Hull Maintenance Technician

Hull Maintenance Technician
Hull Maintenance
DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.
By enrolling in this self-study course, you have demonstrated a desire to improve yourself and the Navy.
Remember, however, this self-study course is only one part of the total Navy training program. Practical
experience, schools, selected reading, and your desire to succeed are also necessary to successfully round
out a fully meaningful training program.
COURSE OVERVIEW: In completing this nonresident training course, you will demonstrate an
understanding of course materials by correctly answering questions on the following: safety; ship repair;
woodworking cuts and joints; small boat repair and deck coverings; tools and equipment; metallurgy;
introduction to cutting and welding; oxyacetylene cutting and welding; brazing and braze welding; metal-are
welding and cutting; nondestructive tests and inspection of welds; sheet metal layout and fabrication;
structural steel fabrication; shop mathematics; piping systems; piping system repairs; and sewage systems.
THE COURSE: This self-study course is organized into subject matter areas, each containing learning
objectives to help you determine what you should learn along with text and illustrations to help you
understand the information. The subject matter reflects day-to-day requirements and experiences of
personnel in the rating or skill area. It also reflects guidance provided by Enlisted Community Managers
(ECMs) and other senior personnel, technical references, instructions, etc., and either the occupational or
naval standards, which are listed in the Manual of Navy Enlisted Manpower Personnel Classifications
and Occupational Standards, NAVPERS 18068.
THE QUESTIONS: The questions that appear in this course are designed to help you understand the
material in the text.
VALUE: In completing this course, you will improve your military and professional knowledge.
Importantly, it can also help you study for the Navy-wide advancement in rate examination. If you are
studying and discover a reference in the text to another publication for further information, look it up.
1995 Edition Prepared by
HTC Michael Smart
HTC Arnold L. Steber
Published by
NAVSUP Logistics Tracking Number
1. Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
2. Ship Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3. Woodworking Cuts and Joints . . . . . . . . . . . . . . . . . . . . 3- 1
4. Small Boat Repair and Deck Coverings . . . . . . . . . . . . . . . 4-1
5. Tools and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
6. Metallurgy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7. Introduction to Welding and Cutting . . . . . . . . . . . . . . . . . 7-1
8. Oxyacetylene Cutting and Welding . . . . . . . . . . . . . . . . . . 8- 1
9. Brazing and Braze Welding . . . . . . . . . . . . . . . . . . . . . . 9-1
10. Metal-Arc Welding and Cutting . . . . . . . . . . . . . . . . . . 10- 1
11. Nondestructive Tests and Inspection of Welds . . . . . . . . . . . 11-1
12. Sheet Metal Layout and Fabrication . . . . . . . . . . . . . . . . 12-1
13. Structural Steel Fabrication . . . . . . . . . . . . . . . . . . . . . 13-1
14. Shop Mathematics . . . . . . . . . . . . . . . . . . . . . . . . . .
15. Piping Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .
16. Piping System Repairs . . . . . . . . . . . . . . . . . . . . . . . 16-1
17. Sewage Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1
II. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AII-1
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Upon completion of this chapter, you will be able to do the following:
Identify the basic safety requirements, and how the role of responsibility
starts with you.
Identify various sources of information regarding safety.
Identify various warning signs, placards, tags, and labels.
Describe the safety precautions to be followed when working on or with
electrical welding equipment.
Describe the safety procedures to follow when working with chemicals and
Describe the safety procedures to follow when working on or with various
tools, equipment, and machinery.
Describe the safety procedure, and precautions to follow before and after
hotwork operations.
Describe the safety procedures to follow when performing cutting
Describe the Navy’s Hearing Conservation and Noise Abatement
Describe the Navy’s Heat Stress Control Program.
strictly observed. The primary goals of an effective
safety program are to protect personnel and material
and to ensure that unsafe equipment operations do not
occur. As a petty officer or chief petty officer, you have
the responsibility to recognize unsafe conditions and to
take appropriate actions to correct any discrepancies.
It is Navy policy to provide a safe and healthy
work place for all personnel. These conditions can be
ensured through an aggressive and comprehensive
occupational safety and health program fully endorsed
by the Secretary of the Navy and implemented through
the appropriate chain of command. Safety begins with
A number of safety precautions that are likely to
concern HTs at one time or another are listed in this
chapter. You need to observe all of these precautions.
The purpose of this chapter is not to teach safety but to
stress emphatically to all personnel that to work safely
and to be safety conscious at all times is as much a part
of their trade as may be any of its finer secrets or skills
and to keep forever in mind, in the execution of their
duties, this one simple slogan: WORK SAFELY.
The material discussed in this chapter stresses the
importance of observing standard safety precautions and
procedures. As a Hull Technician, you will be working
with different types of equipment, such as electrical
welding equipment. All electrical equipment is
hazardous; therefore, all safety precautions must be
real instrument of safety is a careful and
safety-conscious worker.
All individuals have the responsibility to understand
and observe safety standards and regulations that are
established for the prevention of injury to themselves
and other people and damage to property and
equipment. As an individual, you have a responsibility
to yourself and to your shipmates to do your part in
preventing mishaps. As a petty officer or chief petty
officer, you have the responsibility of setting a good
example; you cannot ignore safety regulations and
expect others to follow them.
All personnel should make it a habit to observe the
following “ten commandments of safety.”
1. LEARN the safe way to do your job before you
2. THINK safety and ACT safely at all times.
3. OBEY safety rules and regulations—they are
for your protection.
Personnel should always observe the following
safety practices:
4. WEAR proper clothing and personal protective
equipment (PPE).
Observe all posted operating instructions and
safety precautions.
5. CONDUCT yourself properly at all
times—horseplay is prohibited.
Report any unsafe condition or any equipment
or material deficiency you think might be
6. OPERATE only the equipment you are
authorized to use.
Warn others of hazards and the consequences
of their failing to observe safety precautions.
7. INSPECT tools and equipment for safe
condition before starting work.
Wear or use approved protective clothing or
protective equipment.
8. ADVISE your superior promptly of any unsafe
conditions or practice.
Report any injury or evidence of impaired
health that occurs during your work or duty to
your supervisor.
9. REPORT any injury immediately to your
10. SUPPORT your safety program and take an
active part in safety meetings.
Exercise reasonable caution as appropriate to
the situation in the event of an emergency or
other unforseen hazardous conditions.
In addition to these rules, there are other good work
habits that will help you perform your job more
efficiently as well as safely.
Inspect equipment and associated attachments
for damage before using the equipment. Be sure
the equipment is suited for the job.
Remember: Mishaps seldom just happen; they are
caused. Another point to remember is to never let
familiarity breed contempt. Most mishaps could have
been prevented had the individuals involved heeded the
appropriate safety precautions. Preventing mishaps that
are avoidable will help you in the Navy and possibly
determine whether or not you survive.
Lessons learned from many industrial mishaps that
have been investigated and studied have been compiled
into easily understandable booklets and pamphlets
published to propagate and market safety awareness and
familiarity with various rules and regulations. Also,
many safety devices and aides of all types have been
developed to save lives and to provide a means for
avoiding mishaps. However, all of the safety literature,
devices, or aides that have been developed thus far and
those that will be developed in the future can only help
the one real instrument of safety play its part. That one
Promoting safety will require you to become safety
conscious to the point that you automatically consider
safety in every job or operation. By safety reminders
Naval Ships’ Technical Manual, chapter
074—Provides general welding safety precautions.
and your personal example, you pass this safety
consciousness on to other personnel.
Personnel are also advised and informed on mishap
prevention through the following periodicals:
Safety precautions, as all rules, laws, or regulations,
must be enforced. It is your duty to take appropriate
action any time you see someone disregarding a safety
precaution. You should ensure that all jobs are done
according to applicable safety precautions.
Fathom magazine, the afloat safety review, is
published bimonthly for the professional benefit of all
hands by the Navy Safety Center. Fathom presents the
most accurate information currently available on the
subject of shipboard mishap prevention.
Doing a job the safe way in some cases may take
a little longer or be a little more inconvenient, however,
there is no doubt as to the importance of doing it this
Ships’ Safety Bulletin is published monthly by the
Navy Safety Center. This bulletin contains articles on
shipboard safety problems, trends, mishap briefs, and
Deckplate magazine is published bimonthly by the
Naval Sea Systems Command. This magazine contains
information on the design, construction, conversion,
operation, maintenance, and repair of naval vessels and
their equipment. It also contains articles on safety
hazards and their prevention.
To be an effective petty officer and supervisor, you
should become familiar with the types of safety
programs implemented throughout the Navy. You
should also be familiar with all safety directives and
precautions concerning your division. Safety
instructions vary from command to command. This
makes it impossible to give you a complete listing of
manuals and instructions with which you should be
familiar. Besides studying the information on safety
described in this chapter and throughout this training
manual, you should read and have knowledge of the
safety information in the following references:
Flash, a monthly mishap prevention bulletin,
provides a summary of research from selected reports
of submarine hazards to assist in the prevention
program. It is intended to give advance coverage of
safety-related information while reducing individual
reading time.
Standard Organization and Regulations of the
U. S. Navy, OPNAVINST 3120.32B, chapter
7—Outlines the safety program and the safety
These publications, as well as notices and
instructions distributed by the cognizant bureaus, make
excellent reference materials. When these publications
are available, you should read them and incorporate
them into your training program.
Navy Occupational Safety and Health
(NAVOSH) Program Manual for Forces Afloat,
OPNAVINST 500.19C—Provides general
shipboard safety precautions and specific
occupational health program guidance.
Other sources of safety information that you will be
dealing with on a day-to-day basis in your work as a
Hull Technician are manufacturers’ technical manuals
and PMS maintenance requirement cards (MRCs).
Navy Occupational Safety and Health
(NAVOSH) Program Manual, OPNAVINST
5100.23C—Encompasses all safety disciplines,
such as systems safety, aviation safety,
weapons/explosives safety, off-duty safety
(recreation, public, and traffic), and
occupational safety and occupational health.
These are not all of the safety resources that are
available to you. However, these sources give you a
good starting point from which you can expand your
knowledge of safety procedures. The Naval Safety
Supervisor, NAVEDTRA 12971, is also a very good
resource for strengthening your awareness of safety
Warning signs, placards, tags, labels, and suitable
guards/markings should be provided to prevent
personnel from coming into accidental contact with
dangerous equipment; for warning personnel of the
possible presence of airborne contaminants as a result
of grinding operations; and for warning personnel of
other dangers that may cause injury to them. Equipment
installations should not be considered complete until
appropriate warning signs have been posted in full view
of operating and maintenance personnel.
Warning signs (red/white) and caution signs
(yellow/black) should be located in an area where
known hazardous conditions exist or may exist. Some
of the areas that are hazardous aboard ship include
workshops, pump rooms, and machinery spaces.
However, hazards may be encountered anywhere aboard
Figure 1-1.—A warning placard.
Remember, once a tag or label is used, it should
only be removed by signed authorization of the
authorizing officer. You should always follow your
command’s procedures for logging and recording
tag-out actions.
Signs designating an entire space as hazardous must
be posted at eye level or above in full and clear view of
entering personnel. Signs designating a specific piece of
equipment as hazardous must be posted on or near
equipment (in full view of the equipment operator) that
is particularly dangerous.
Markings consisting of paint or tape are used to
designate safe traffic lanes, operator caution areas,
operator working areas, and observer safe areas.
Warning placards (fig. l-l) should be located on the
door to the entrance of any space where noise levels are
consistently high, requiring single- or double-hearing
protection. A warning placard should also be displayed
on all portable equipment capable of emitting noise in
excess of 84 dB(A) when operated. Remember that the
messages are aimed at YOU. It is your responsibility to
“read and heed.”
Safe traffic lanes are designated in workshops.
These lanes start and stop at all exits and entrances for
workshops and are marked by continuous white lines,
3 inches wide, painted on the deck.
Operator caution areas, operator working areas, and
observer safe areas are designated for each equipment
working area deemed hazardous. Operator caution areas
are marked by a continuous yellow tine, 3 inches wide,
outlining the caution area. Operator work areas are
marked by painting the deck yellow in areas where it is
safe for an operator of machinery or equipment. The
outer perimeter of this area is designated by alternate
black and yellow lines, or checkerboard pattern, 3
inches wide. Observer safe areas are designated as all
areas outside of this perimeter and are the normal color
of the deck within the space.
Tags and labels are used in the Navy to identify a
defective piece of equipment or instrument. Tags and
labels are also used to ensure the safety of personnel
and to prevent improper operation of equipment. They
will be posted according to authorized procedures and
must not be removed or violated without proper
authorization and adequate knowledge of the
The use of tags and labels is not a substitute for
other safety measures, such as locking valves or
removing fuses from a fuse panel. Also, tags or labels
associated with tag-out procedures must never be used
for anything other than their intended purpose.
Eye hazardous areas are marked with a black and
yellow checkerboard, or chevron, pattern and a label
plate made up of black letters on a yellow background
that reads: “WARNING EYE HAZARD.”
Respirators and masks protect personnel from the
inhalation of many toxic materials. The wearing of a
respirator is required when performing grinding,
welding, brazing, and wood operations. It is also
required when you are exposed to high concentrations
of hazardous vapors or fumes. Respirators and masks
provide protection against aerosols, dusts, fumes, and
vapors. Some respirators are disposable and others are
reusable. A filter or disposable respirator protects
against dust; and the reusable chemical cartridge type of
air-purifying respirator protects against gaseous
contaminants. Particle masks, air line hose masks, and
vapor masks are also reusable.
Safety equipment is for you. It will protect you
from injury and may possibly save your life. Some of
the more common types of safety equipment for your
personal protection are described in the following
Proper eye protection is of the highest importance
for all personnel. Eye protection is necessary because of
hazards caused by infrared and ultraviolet radiation or
by flying objects such as sparks, globules of molten
metal, or chipped concrete and wood. These hazards are
always present during welding, cutting, soldering,
chipping, grinding, and a variety of other operations. It
is absolutely necessary for you to use eye protection
such as helmets, face shields, goggles, and safety
glasses during eye-hazard operations. Appropriate use
of goggles will limit eye hazards. Some goggles have
plastic windows that resist shattering upon impact.
Others are designed to limit harmful infrared and
ultraviolet radiation from arcs or flames by use of
appropriate filter lenses. Remember, eye damage can be
extremely painful. Protect your eyes.
HTs perform plan, supervise, and perform tasks
necessary for fabrication, installation, and repair of all
types of shipboard structures, plumbing, and piping
systems. This includes performing welding, cutting,
brazing, and grinding operations. Because of this, HTs
must be aware of the general and specific safety
precautions involved in their work. The following
paragraphs will discuss some of the safety hazards and
precautions that you should be familiar with.
Proper hearing protection is a must when working
with or around certain types of power tools. Some tools
are capable of producing dangerously high noise levels
which, if ignored, can result in serious hearing loss or
injury. You should use hearing protection regularly.
Examples of hearing protection are aural hearing
protectors, single-flanged earplugs, double-flanged
earplugs, triple-flanged earplugs, and foam earplugs.
Before using any machine or piece of equipment,
you must be familiar with all safety precautions
pertaining to its operation. Carelessness around any
moving machinery is extremely dangerous. When
moving machinery is equipped with sharp cutting tools,
the dangers are greatly increased. The following list
includes some of the more general safety precautions
for machines/equipment. Specific safety and operating
precautions should be posted in plain sight on or by
every machine.
Safety shoes/boots protect and prevent injury or loss
of toes. Some safety shoes are designed to limit damage
to your toes or feet from falling objects. A steel plate is
placed in the toe area of such shoes so that your toes
are not crushed if an object falls on them. Other safety
shoes are designed for use where danger from sparking
could cause an explosion. Such danger is minimized by
elimination of all metallic nails and eyelets and the use
of soles that do not cause static electricity. Examples of
safety shoes are boondockers, high-steel toe, and molder
—Before operating a machine, make sure there is
plenty of light to work by.
—Do not distract the attention of a machine
—Do not lean against any machine that is in
motion. Keep clear of all gears, belts, and other moving
parts. Never remove the guards from any part of an
operating machine.
—When operating the brake press, place hands
under the plate. Be sure the head and upper body are
clear from the plate. Do not lean over the work while
bending the plate.
—Never start a machine unless you are thoroughly
familiar with its operation.
—Do not attempt to clean, adjust, or repair a
machine while it is in motion. Shut off the power
supply to the machine. NEVER attempt to clean
running gears.
—Magnetic particle test equipment is capable of
producing current in excess of 600 amperes. Follow all
electrical safety precautions; failure to do so may result
in serious injury or death.
—PROTECT YOUR EYES. Do not hold your head
too close to the cutting tool-flying bits of metal or
scale may get into your eyes. Always wear goggles
when there is any danger of flying particles getting in
your eyes; for example, when using a grinding or
drilling machine.
—In all machine work, stress SAFETY first,
ACCURACY second, and SPEED last. Excessive
speed is both dangerous and unproductive.
appropriate hearing protection. Either aural hearing
protectors (mickey mouse ears) or ear plugs will reduce
the noise from running machinery. Prolonged exposure
may damage your hearing.
Safety is a very important factor in the use of
portable power tools and cannot be overemphasized.
The hazards associated with the use of portable power
tools are electric shock, cuts, flying particles,
explosions, and so on. Because you will be using
portable power drills, hammers, and grinders in the
shop and out on the job, you should be thoroughly
familiar with the operation and care of these tools and
with all applicable safety precautions. The portable
power tools that you use may be powered by electric
motors or by air (pneumatic) motors. Whether
electrically powered or air powered, the tools and
procedures for using them are basically the same. Safe
pratice in the use of these tools will reduce or eliminate
the mishap potential. By observing the following safety
guidelines, you can ensure maximum benefits from the
tools you use and reduce to a minimum the chances of
serious injury.
—Keep your fingers away from the cutting edges
when the machine is in operation; otherwise, you could
lose some fingers.
—Do not wear gloves or loosely hanging clothes.
They can be caught by moving parts of the shop
machinery and cause serious injuries. Keep your
sleeves rolled down and buttoned up tightly Do not
wear neckties or loose neckerchiefs. If clothing becomes
caught in a machine, shut off the power immediately.
—When using portable electric equipment around
machine tools, take special care so that electrical cords
are clear of moving parts.
—Do not exceed the recommended depth of cut,
cutting speeds, and feeds.
Never operate any portable power tools unless
you are completely familiar with their controls
and features.
—Keep areas around machines clear of obstructions
and ensure a nonskid surface is available for the
equipment operator.
Inspect all portable power tools before using
them. See that they are clean and in good
—Remove chips with a brush or other suitable tool;
never by hand or with compressed air.
Make sure there is plenty of light in the work
area. Never work with power tools in dark
areas where you cannot see clearly.
—When operating the brake press, always
disconnect the foot switches and ensure that the
eccentrics are in the bottom stroke before setting or
adjusting the punch and die.
Before connecting power tools to a power
source, be sure the tool switch is in the OFF
—Place eccentrics on the bottom center of the drop
shear bed.
When operating a power tool, give it your full
and undivided attention.
Exposure to chemical hazards may cause significant
health problems. Solvents are capable of damaging your
respiratory system in cases of prolonged inhalation.
Chemicals and solvents come in the form of gas, vapor,
mist, dust, or fumes. Materials ordinarily thought to be
safe may be rendered hazardous under certain use
conditions by the uninformed user. As an HT, you will
inevitably come into contact with various
chemicals/solvents. Most of these chemicals will have
some type of hazard associated with them. Among these
hazards are irritants, toxics, corrosives, and flammables.
Do not distract or in any way disturb another
person while they are operating a power tool.
Never try to clear a jammed power tool until it
is disconnected from the power source.
After using a power tool, turn off the power,
disconnect the power source, wait for all
movement of the tool to stop, and then remove
all waste and scraps from the work area. Store
the tool in its proper place.
Personnel engaged in the handling and use of
chemicals must always use appropriate protective
equipment for the class of chemical being used.
Do not allow power cords to come in contact
with sharp objects, nor should they kink or
come in contact with oil, grease, hot surfaces,
or chemicals.
Such protective equipment includes, but is not
limited to, the following items:
Never use a damaged cord. Replace it
Rubber gloves, boots, and aprons
Check electrical cables and cords frequently for
overheating. Use only approved extension
cords, if needed.
Air masks, respirators, and filter masks
Eye protection, goggles, and face shields
Always connect the cord of a portable power
tool into the extension cord before the
extension cord is inserted into a live receptacle.
Protective skin creams, when sensitive or skin
irritants are used
Any other protective equipment that is
Always unplug the extension cord from the
receptacle before the cord of the portable power
tool is unplugged from the extension cord.
Following is a list of safety precautions that you
should observe when using and handling chemicals/
See that all cables and cords are positioned
carefully so they do not become tripping
—Review the Material Safety Data Sheet (MSDS)
for any chemical prior to using or handling it.
Treat electricity with respect. If water is present
in the area of electrical tool operation, be
extremely cautious and, if necessary, disconnect
the power tool.
—Do not work alone in a poorly ventilated space.
—Do not apply solvents to warm or hot equipment,
since this increases the potential evaporation rate
making it more hazardous.
The air pressure for any pneumatic tool must
not exceed 90 psi.
—Never use a solvent in the presence of any open
Never point the air hose at another person.
When working with pneumatic tools, always
stand so you are properly balanced while
working so you will not slip and lose control of
the tool.
—Place a fire extinguisher close by, ready for use.
—Hold the nozzle close to the object being sprayed.
be provided, organic respirators are required for
protection against vapors.
—Personnel who use potential irritants, such as
epoxy, resins, and hardeners, should avoid direct skin
contact. Should contact be made with an irritant, the
area should be washed thoroughly with soap and water.
Irritants require no special storage other than that
required by their other properties, such as flammability
or toxicity.
—Always wash exposed skin areas thoroughly
when you are finished working.
—All hazardous materials used by the Navy is
required to be correctly labeled.
As an HT, one of your main jobs will be welding.
You must use extreme care when welding. Safety must
always be practiced by people working around or with
arc welding equipment. Welding performed with proper
safety equipment presents no great safety hazards. You
should learn the correct procedures for arc welding in
order that the hazards that exist may be properly
observed and eliminated, and, if possible, injury
—In compliance with the Occupational Safety and
Health Administration (OSHA). a fire resistant
hydraulic fluid must be used when filling the reservoir
of a hydraulic power rig.
—Dispose of solvent-soaked rags in a container
designed for flammable disposal. Wear rubber
protective gloves when handling solvents and be sure
that ventilation is adequate.
The chief hazards to be avoided in arc welding are
as follows:
—Do not allow eating, drinking, or smoking in the
area where solvents are being used. Any chemicals or
solvents should be handled with caution.
Radiation from the arc, in the form of
ultraviolet and infrared rays
Flying sparks and globules of molten metal
—Cutting and grinding of reinforced plastic
laminates generate a fine dust that irritates the skin and
eyes. Inhalation of the dust should be avoided.
Electric shock
Metal fumes
—Keep chemical containers clearly labeled and
tightly covered when they are not in use. When mixing
a polyester resin, never mix the catalyst and accelerator
directly together or an explosion may result. Always
mix chemicals according to instructions.
Radiation from the arc presents some dangers. Eyes
must be protected from radiation from the arc by use of
an arc welding helmet or face shield with approved
—Many solvents give off toxic vapors and are
dangerous upon contact with the skin. Wear respirators
and rubber gloves, as appropriate, when handling
solvents and ensure that the working area is well
Your face, hands, arms, and other skin surfaces
must be covered to prevent exposure to the radiation.
Gloves should be worn and other parts of the body
covered by clothing of sufficient weight to shut out the
rays of the arc. Without proper clothing, burns
comparable to sunburn will result.
—Do not use solvents and degreasers of the
halogen family (for example, freon and trichloroethane)
near the cutting operation, because light from the arc
can break them down into toxic components (phosgene
When possible, all arc welding operations should be
shielded so that no one may accidentally look directly
at the arc or have it shine or reflect into their eyes. An
arc “flash” may cause a person to be temporarily
blinded, by causing the person to see a white spot
similar to a photographer's flash. The severity of an arc
flash and the time it will take to recover varies with the
length of time a person was exposed to the arc. A long
—If clothing becomes contaminated, remove it and
wash it thoroughly before reuse.
—When working in confined spaces, be sure there
is adequate ventilation. Where such ventilation cannot
exposure has been known to cause permanent damage
to the retina of the eye. If someone is severely
“flashed,” special treatment should be administered at
once by medical personnel.
process will burn skin. Gas welding can also cause
radiation burns due to infrared rays emitted by the red
hot material. Flame-resistant or flame-retardant clothing
must be worn and the hair protected at all times.
Arc welding is usually accompanied by flying
sparks, which present a hazard if they strike unprotected
skin, lodge on flammable clothing, or hit any other
flammable material. When arc welding, you should
wear suitable weight clothing and cuffless trousers.
Cover your pockets so they will not collect sparks, and
remove any flammable materials, such as matches,
plastic combs, or gas lighters. You should also ensure
that you wear the proper foot protection. High top boots
or boondockers with steel toes should be worn.
—Fluxes used in certain welding and brazing
processes produce vapors that are irritating to the eyes,
nose, throat, and lungs. Oxides produced by these
volatile elements are very poisonous. Therefore,
welding must be performed in a well-ventilated area
and approved safety goggles must always be worn. The
darkest shade of the goggles that still show a clear
outline of the work without producing eyestrain are
recommended. Sun glasses are not adequate.
—Do not smoke or work near hot surfaces or open
Hot metal will cause severe bums and should never
be handled with bare hands until it has cooled naturally
or has been quenched in the quenching tank. Therefore,
you should use leather gloves with tight fitting cuffs
that fit over the sleeves of the jacket. Many welders
wear a full set of leathers that consists of the following:
Soldering or brazing with or on alloys containing
cadmium or beryllium can be extremely hazardous.
Fumes from cadmium or beryllium compounds are
extremely toxic. In fact, several deaths have been
reported from inhaling cadmium oxide fumes.
Jacket or set of sleeves
Gauntlet gloves
Skin contact with cadmium and beryllium should
also be avoided. An expert in industrial hygiene should
be consulted whenever cadmium or beryllium
compounds are to be used or when repairs are to be
made on parts containing the metals.
Welders hat liner
Fluxes containing fluoride compounds are also
toxic. Good ventilation is essential when soldering or
brazing and the operator must always observe good
safety practices.
Following is a list of other safety precautions that
you should keep in mind when performing welding
A common hazard when soldering is exposure of
the skin, eyes, and clothing to acid fluxes. You should
observe the following safety precautions when soldering
or brazing:
—The possibility of dangerous electric shock can be
avoided by using insulated electrode holders and
wearing dry leathers and gloves. When possible, avoid
using arc welding equipment in wet or damp areas.
—Always work in a way that flux will not be
spilled on the skin or clothing.
—Use a welding helmet with a No. 10 or No. 12
shade along with good quality work clothing and
gauntlet-type gloves. Wear ear protection when
sound-pressure levels exceed 84 dB(A).
—Always wear chemical splashproof goggles,
rubber gloves, and long sleeves when using cleaning
solutions, pickling solutions, or acids.
—In gas welding, the high temperatures of the
welding flame and the sparks created by the welding
—If at any time you are exposed to any chemical
solutions, acids, or fluxes, wash the affected area at
once, and seek medical attention immediately.
—Remember, heating soldering coppers sometimes
presents a fire hazard if an open flame is used. Be sure
all flammable material is removed or kept away from
the heating flames.
You must always observe safety precautions when
working on equipment or operating machinery. Because
of the danger of electric shock from equipment and
operating machinery, the possibility of receiving burns
from welding, and the possibility of a body part being
cut when performing cutting operations, it is important
that you know and be able to perform the proper action
when a mishap occurs. The following paragraphs will
briefly describe some of first-aid techniques that you
should be familiar with.
—Make sure there are no flammable vapors present,
such as gasoline, acetylene, or other flammable gases,
where the hot work is to be performed.
—No job should ever be started until all safety
precautions have been taken, and the fire marshal
notified, if applicable.
Methods of resuscitating or reviving an electrical
shock victim include artificial ventilation (to reestablish
breathing) and cardiopulmonary resuscitation (to
reestablish heartbeat and blood circulation).
Another part of your job will involve cutting
operations such as oxyacetylene cutting and plasma arc
cutting. Observe the following safety precautions when
performing any cutting operation:
Artificial Ventilation
A person who has stopped breathing is not
necessarily dead, but is in immediate critical danger.
Life depends on oxygen that is breathed into the lungs
and then carried by the blood to every body cell. Since
body cells cannot store oxygen, and since the blood can
hold only a limited amount (and only for a short time),
death will surely result from continued lack of
—Never place hands or fingers between the metal
plate and the bed. Never place hands under the
holddowns or knife. Ensure that all personnel are clear
from the piece being cut.
—Ensure that the plate is supported so that injuries
to personnel can be avoided if the cut end of the metal
falls away.
The heart may continue to beat and the blood may
still be circulated to the body cells for some time after
breathing has stopped. Since the blood will, for a short
time, contain a small supply of oxygen, the body cells
will not die immediately. Thus, for a very few minutes,
there is some chance that the person’s life may be
saved. A person who has stopped breathing but who is
still alive is said to be in a state of respiratory failure.
The first-aid treatment for respiratory failure is called
artificial ventilation/respiration.
—When using oxyacetylene cutting equipment,
ensure that the work area is gas-free. This is particularly
important when working in bilges and other spaces
where dangerous vapors may collect.
—The high-pressure oxygen stream used in cutting
with an oxyacetylene torch can throw molten metal for
a distance of 50 to 60 feet. Always post a fire watch to
protect the surrounding areas and personnel.
—When using oxyacetylene cutting equipment,
ensure that any interfering system has been removed
and tagged out, if necessary.
The purpose of artificial ventilation is to provide a
method of air exchange until natural breathing is
reestablished. Artificial ventilation should be given only
when natural breathing has stopped; it must NOT be
given to any person who is still breathing. Do not
assume that breathing has stopped merely because a
person is unconscious or because a person has been
rescued from an electrical shock Remember, DO NOT
—Install all covers, insulators, and handles before
attempting to operate the plasma arc cutting equipment.
—When using plasma arc cutting equipment, open
all primary disconnect switches before charging any
electrical connections.
Wounds are classified according to their general
condition, size, location, how the skin or tissue is
broken, and the agent that caused the wound.
methods of administering artificial ventilation: mouthto-mouth and mouth-to-nose.
For additional information on performing artificial
ventilation, refer to Standard First Aid Training Course,
When you consider the manner in which the skin or
tissue is broken, there are four general kinds of wounds:
abrasions, incisions, lacerations, and punctures.
Cardiopulmonary Resuscitation
When there is a complete stoppage of heart
function, the victim has suffered a cardiac arrest. The
signs include the absence of a pulse, because the heart
is not beating, and the absence of breathing. In this
situation, the immediate administration of
cardiopulmonary resuscitation (CPR) by a rescuer using
correct procedures greatly increases the chances of a
victim’s survival.
Abrasions are made when the skin is rubbed or
scraped off. Rope bums, floor burns, and skinned knees
or elbows are common examples of abrasions. There is
usually minimal bleeding or oozing of clear fluid.
Incisions, commonly called cuts, are wounds made
with a sharp instrument, such as a knife, razor, or
broken glass. Incisions tend to bleed very freely because
the blood vessels are cut straight across.
CPR consists of external heart compression and
artificial ventilation. The compressions are performed
by pressing the chest with the heel of your hands, and
the lungs are ventilated either by mouth-to-mouth or
mouth-to-nose techniques. To be effective, CPR must
be started within 4 minutes of the onset of cardiac
Lacerations are wounds that are torn, rather than
cut. They have ragged, irregular edges and masses of
torn tissue underneath. These wounds are usually made
by blunt forces, rather than sharp objects. They are
often complicated by crushing of the tissues as well.
CPR should not be attempted by a
rescuer who has not been properly trained.
Improperly done, CPR can cause serious
damage to a victim. Therefore, CPR is
NEVER practiced on a healthy individual.
For training purposes, a training aid is used
instead. To learn CPR, you should take an
approved course from a qualified CPR
Punctures are caused by objects that penetrate some
distance into the tissues while leaving a relatively small
surface opening. As a rule, small punctures do not bleed
freely; however, large puncture wounds may cause
severe internal bleeding.
A puncture wound can be classified as penetrating
or perforating. A perforation differs from a penetration
in that it has an exit as well as an entrance site.
For additional information on administering CPR,
refer to Standard First Aid Training Course,
For additional information on the treatment of
wounds refer to Standard First Aid Training Course,
A wound, or breaking of the skin, is another
problem that could be the result of an electrical shock.
You could accidentally suffer an electrical shock, which
could cause a loss of balance. This could result in a
minor or serious injury. Because you could be in a
critical situation to save someone’s life, or even your
own, you should know the basics of first aid.
The first-aid methods that are used to stop serious
bleeding depend upon the application of pressure.
Pressure may be applied in three ways: (1) directly to
the wound, (2) at key pressure points throughout the
body, and (3) with a tourniquet.
body, since its use in these locations would result in
greater injury or death. A tourniquet should be used on
an injured limb only as a last resort for severe,
life-threatening hemorrhaging that cannot be controlled
by any other method. A tourniquet must be applied
ABOVE the wound—that is, towards the trunk—and it
must be applied as close to the wound as practicable.
Direct Pressure
You should try the direct-pressure method first to
control bleeding. Place a sterile first-aid dressing, when
available, directly over the wound. Tie the knot only
tight enough to stop the bleeding, and firmly fasten it
in position with a bandage. In the absence of sterile
dressings, use a compress made with a clean rag,
handkerchief, or towel to apply direct pressure to the
wound, as in figure 1-2. If the bleeding does not stop,
firmly secure another dressing over the first dressing, or
apply direct pressure with your hand or fingers over the
dressing. Under no circumstances is a dressing to be
removed once it is applied.
Any long, flat material can be used as a band for a
tourniquet—belts, stockings, flat strips of rubber, or a
neckerchief. Only tighten the tourniquet enough to stop
the flow of blood. Use a marker, skin pencil, crayon, or
blood, and mark a large T on the victim’s forehead.
Pressure Points
If the direct-pressure method does not stop the
bleeding, use the pressure point nearest the wound, as
shown in figure 1-3. Bleeding from a cut artery or vein
may often be controlled by applying pressure to the
appropriate pressure point. A pressure point is a place
where the main artery to the injured part lies near the
skin surface and over a bone. Pressure at such a point
is applied with the fingers or with the hand; no first-aid
materials are required. Pressure points should be used
with caution, as they may cause damage to the limb as
a result of an inadequate flow of blood. When the use
of pressure points is necessary, do not substitute them
for direct pressure; use both.
Remember, a tourniquet is only used as
a last resort to control bleeding that cannot
be controlled by other means. Tourniquets
should be removed as soon as possible by
medical personnel only.
The causes of burns are generally classified as
thermal, electrical, chemical, or radiation. Whatever the
cause, shock always results if the burns are extensive.
Thermal burns are caused by exposure to intense
heat, such as that generated by fire, bomb flash,
sunlight, hot liquids, hot solids, and hot gases. Their
care depends upon the severity of the bum and the
percentage of the body area involved.
Use of a Tourniquet
A tourniquet is a constricting band that is used to
cut off the supply of blood to an injured limb. It cannot
be used to control bleeding from the head, neck, or
Electrical burns are caused by electric current
passing through tissues or the superficial wound caused
by electrical flash. They may be far more serious than
they first appear. The entrance wound may be small;
but as electricity penetrates the skin, it burns a large
area below the surface. Usually there are two external
burn areas: one where the current enters the body, and
another where it leaves.
Chemical burns for the most part are not caused by
heat, but by direct chemical destruction of body tissues.
When acids, alkalies, or other chemicals come in
contact with the skin or other body membranes, they
can cause injuries that are generally referred to as
chemical burns. The areas most often affected are the
extremities, mouth, and eyes. Alkali burns are usually
Figure 1-2.—Direct pressure.
Figure 1-3.—Pressure points for control of bleeding.
more serious than acid burns, because they penetrate
deeper and burn longer. When chemical burns occur,
emergency measures must be carried out immediately.
Do not wait for the arrival of medical personnel.
Radiation burns are the result of prolonged
exposure to the ultraviolet radiation. First- and
second-degree burns may develop. Treatment is
essentially the same as that for thermal bums.
Classification of Burns
Emergency Treatment of Burns
Burns are classified in several ways: by the extent
of the burned surface, by the depth of the burn, and by
the cause of the burn. The extent of the body surface
burned is the most important factor in determining the
seriousness of the burn and plays the greatest role in the
victim's chances of survival.
The degree of the burn, as well as the skin area
involved, determines the procedures used in the
treatment of burns. Large skin areas require a different
approach than small areas. To estimate the amount of
skin area affected, the extent of burned surface, the
“Rule of Nines” (fig. 1-5) is used. These figures aid
in determining the correct treatment for the burned
Burns may also be classified as first, second, or
third degree, based on the depth of skin damage (fig.
1-4). First-degree burns are mildest. Symptoms are
reddening of the skin and mild pain. Second-degree
burns are more serious. Symptoms include blistering of
the skin, severe pain, some dehydration, and possible
shock. Third-degree burns are worst of all. The skin is
destroyed and possibly the muscle tissue and bone in
severe cases. The skin may be charred or it may be
white or lifeless. This is the most serious type of burn,
as it produces a deeper state of shock and will cause
more permanent damage. It is usually not as painful as
a second-degree burn because the sensory nerve endings
have been destroyed.
As a guideline, consider that burns exceeding 15
percent of the body surface will cause shock; burns
exceeding 20 percent of the body surface endanger life;
and bums covering more than 30 percent of the body
surface are usually fatal if adequate medical treatment
is not received.
Minor burns, such as first-degree burns over less
than 20 percent of the body area and small
second-degree bums, do not usually require immediate
medical attention unless they involve the facial area.
Figure 1-4.—First-, second-, and third-degree burns.
used because lint may contaminate and further irritate
the injured tissue. When hands and feet are burned,
dressings must be applied between the fingers and toes
to prevent skin surfaces from sticking to each other.
Do not attempt to break blisters, and do not
remove shreds of tissue or adhered particles of charred
clothing. Never apply greasy substances (butter, lard, or
petroleum jelly), antiseptic preparations, or ointments.
If the victim is conscious and not vomiting, prepare
a weak solution of salt (1 teaspoon) and baking soda
(l/2 teaspoon) in a quart of warm water. Allow the
victim to sip the drink slowly. Aspirin is also effective
for the relief of pain.
Treat for shock. Maintain the victim’s body heat,
but do not allow the victim to become overheated. If
the victim’s hands, feet, or legs are burned, elevate
them higher than the heart.
ELECTRICAL BURNS.—In electrical shock
cases, burns may have to be ignored temporarily while
the patient is being revived. After the patient is revived,
lightly cover the burn with a dry, preferably sterile,
dressing, treat for shock, and transport the victim to a
medical facility.
Figure 1-5.—Rule of Nines.
CHEMICAL BURNS.—To treat most chemical
burns, you should begin flushing the area immediately
with large amounts of water. Do not apply the water
too forcefully. If necessary, remove the victim’s
clothing, including shoes and socks, while flushing.
THERMAL BURNS.—When emergency treatment of the more serious thermal burns is required, first
check the victim for respiratory distress. Burns around
the face or exposure to hot gases or smoke may cause
the airway to swell shut. If facial burns are present,
place the victim in a sitting position to further ease
breathing. Transport the victim with facial burns to a
medical facility as soon as possible.
Water should not be used for alkali burns caused by
dry lime unless large amounts of water are available for
rapid and complete flushing. When water and lime are
mixed they create a very corrosive substance. Dry lime
should be brushed from the skin and clothing.
Isopropyl or rubbing alcohol should be used to treat
acid burns caused by phenol (carbolic acid). Phenol is
not water soluble; therefore, water should only be used
after first washing with alcohol or if alcohol is not
Remove all jewelry and similar articles, even from
unburned areas, since severe swelling may develop
To relieve pain initially, apply cold compresses to
the affected area or submerge it in cold water. Cold
water not only minimizes pain, but also reduces the
burning effects in the deep layers of the skin. Gently
pat dry the area with a lint-free cloth or gauze.
For chemical burns of the eye, flush immediately
with large amounts of fresh, clean water. Acid bums
should be flushed at least 15 minutes, and alkali burns
for as long as 20 minutes. If the victim cannot open the
eyes, hold the eyelids apart so water can flow across the
eyes. After thorough irrigation, loosely cover both eyes
with a clean dressing.
Cover the burned area with a sterile dressing, clean
sheet, or unused plastic bag. Coverings such as blankets
or other materials with a rough texture should not be
Periodic hearing testing must be conducted to
monitor the effectiveness of the program.
The after care for all chemical burns is similar to
that for thermal burns. Cover the affected area and get
the victim to a medical facility as soon as possible.
Navy personnel must be educated on the
Hearing Conservation Program to ensure the
overall success of the program.
RADIATION BURNS.—For first- and seconddegree sunburns, treatment is essentially the same as for
thermal burns. If the bum is not serious, and the victim
does not need medical attention, apply commercially
prepared sunburn lotions and ointments.
Hazardous noise areas and equipment must be so
designated and appropriately labeled. Areas and
equipment that produce continuous and intermittent
sound levels greater than 84 dB(A) or impact or
impulse levels of 140 db peak are considered
For further information on the treatment of burns,
refer to Standard First Aid Training Course,
An industrial hygienist with a noise level meter will
identify the noise hazardous areas. Noise hazardous
areas will be labeled using a hazardous noise warning
decal, NAVMED 6260/2 (fig. 1-6). This decal will be
posted at all accesses. Hazardous noise labels,
NAVMED 6260/2A, are the approved labels for
marking portable and installed equipment.
Historically, hearing loss has been recognized as an
occupational hazard related to certain trades, such as
blacksmithing and boilermaking. Modern technology
has extended the risk to many other activities: using
presses, forging hammers, grinders, saws, internal
combustion engines, or similar high-speed, high-energy
processes. Exposure to high-intensity noise occurs as a
result of either impact noise, such as gunfire or rocket
fire, or from continuous noise, such as jet or propeller
aircraft, marine engines, and machinery.
All personnel that are required to work in
designated noise hazardous areas or with equipment that
produces sound levels greater than 84 db(A) or 140 db
sound/pressure levels are entered in the hearing
conservation program.
Hearing loss has been and continues to be a source
of concern within the Navy, both ashore and afloat.
Hearing loss attributed to such occupational exposure to
hazardous noise, the high cost of related compensation
claims, and the resulting drop in productivity and
efficiency have highlighted a significant problem that
requires considerable attention. The goal of the Navy
Hearing Conservation Program is to prevent
occupational noise-related hearing loss among Navy
personnel. The program includes the following
Work environments will be surveyed to identify
potentially hazardous noise levels and personnel
at risk.
Environments that contain, or equipment that
produces, potentially hazardous noise should be
modified to reduce the noise to acceptable
levels whenever technologically and
economically feasible. When this is not
feasible, administrative control (for example,
stay times) and/or hearing protection devices
should be used.
Figure 1-6.—Hazardous noise warning decal.
As a petty officer or chief petty officer, your role in
the command’s Heat Stress Program involves adhering
to the command’s program and reporting heat stress
conditions as they occur.
You will find further information on hearing
conservation in OPNAVINST 5100.23C, Navy
Occupational Safety and Health (NAVOSH) Program
Manual, and OPNAVINST 5100.19B, Navy
Occupational Safety and Health (NAVOSH) Program
Manual for Forces Afloat.
Primary causes that increase heat stress conditions
are as follows:
Excessive steam and water leaks
All naval personnel receive an initial or reference
audiogram shortly after entering the service. Thereafter,
a hearing test will be conducted at least annually while
you are assigned to a noise hazardous environment.
Hearing tests will also be conducted when there are
individual complaints of difficulties in understanding
conversational speech or a sensation of ringing in the
ears. The annual audiograms will be compared to the
reference (baseline) to determine if a hearing threshold
shift has occurred.
Boiler air casing leaks
Missing or deteriorated lagging on steam
piping, valves, and machinery
Clogged ventilation systems or an inoperative
fan motor
Operating in hot or humid climates
To determine heat stress conditions, permanently
mounted dry-bulb thermometers are installed at key
watch and work stations. Their readings should be
recorded at least once a watch period. When a reading
exceeds 100°F (38°C), a heat stress survey must be
ordered to determine the safe stay time for personnel.
Hearing protective devices should be worn by all
personnel when they must enter or work in an area
where noise levels are greater than 84 dB(A). A
combination of insert earplugs and circumaural muffs,
which provides double protection, should be worn in all
areas where noise levels exceed 104 db(A). Personnel
hearing protective devices should be issued to suit each
A heat stress survey is taken with a wet-bulb globe
temperature (WBGT) meter. You should compare these
readings to the physiological heat exposure limits
(PHEL) chart. After comparing the readings with the
PHEL chart, you will be able to determine the safe stay
time for personnel.
As a petty officer or chief petty officer, you should
have a working knowledge of all aspects of the Heat
Stress Program so you can recognize heat stress
conditions if they occur and take the proper corrective
Heat stress may occur in many work spaces
throughout the Navy. Heat stress is any combination of
air temperature, thermal radiation, humidity, airflow,
and workload that may stress the human body as it
attempts to regulate its temperature. Heat stress
becomes excessive when your body’s capability to
adjust is exceeded. This results in an increase in body
core temperature. This condition can readily produce
fatigue, severe headaches, nausea, and poor physical
and/or mental performance. Prolonged exposure to heat
stress could cause heatstroke or heat exhaustion and
severe impairment of the body’s temperature-regulating
ability. Heatstroke can be life-threatening if not
immediately and properly treated. Recognizing
personnel with heat stress symptoms and getting them
prompt medical attention is an all-hands responsibility.
Further information and guidance of the Navy Heat
Stress Program is contained in OPNAVINST 5100.19B,
Navy Occupational Safety and Health (NAVOSH)
Program Manual for Forces Afloat.
In this chapter, we have described your
responsibilities regarding general and equipment safety,
both as an individual and as a petty officer and chief
petty officer.
procedures for giving first aid to the victim. We have
also briefly discussed the Navy’s Hearing Conservation,
Noise Abatement, and Heat Stress programs.
We have identified various sources of safety
information that are available to you, and provided you
with general and specific safety precautions to assist
you in your day-to-day work as a HT.
Think safety! Always remain alert to possible
We have discussed the danger of electrical shock,
how to rescue a victim from electrical shock, and the
Upon completion of this chapter, you will be able to do the following:
Describe the different types of repairs and alterations on naval ships.
Describe the basic organization of the Repair Department at intermediate
maintenance activities (IMAs).
Describe the basic duties of personnel assigned to IMAs.
Define the Quality Assurance Program.
Explain the quality assurance organization.
Describe the basic requirements for the Quality Assurance Program and
its link to maintenance.
Identify the basic work center organization and the role of the work center
Be able to make a basic time line and identify its component parts.
Identify the structural parts of a ship and discuss the purpose of the parts.
rate are assigned to billets at IMAs performing the basic
functions of ship repair. Therefore, you can expect that
sometime in your career you will be assigned to an
IMA. It is important that you have a basic idea of the
organization and role that an IMA plays in ship’s
Ship's can operate only a certain length of time
without repairs. To keep a ship in prime condition,
constant attention should be given to material upkeep
and definite intervals of time must be allotted for
general overhaul and repair.
Quality assurance (QA) also impacts every maintenance procedure performed by ship’s personnel or maintenance personnel assigned to IMAs. QA has become a
prime consideration when performing maintenance on
any ship’s system. You will use the QA guidelines as
established by your command on a daily basis.
Even when regular maintenance procedures are
carefully followed, accidents and derangements may
necessitate emergency repair work. Defects and
deficiencies that can be corrected by ship’s force should
be dealt with as soon as possible. When repairs are
beyond the capacity of ship’s force to accomplish, aid
must be obtained from a repair activity afloat or ashore.
This chapter covers basic repair, alteration, and
maintenance procedures for naval ships. It also covers
the the IMA organization, the QA program, the the
basic structural parts of a ship.
Ship repair is the basic duty of the HT whether
ashore or afloat. The majority of personnel in the HT
number, location, or relationship of the component
parts. This is true regardless of whether the SHIPALT
is undertaken separately from, incidental to, or in
conjunction with repairs. NAVSEASYSCOM, the forces
afloat, or CNO may originate requests for SHIPALTs.
Corrective maintenance and repairs to ships may be
divided into the general categories of (1) repairs, (2)
alterations equivalent to repairs, and (3) alterations. It
is important that you have an understanding of the
different types of repairs and the difference between a
repair and an alteration.
NAVSEASYSCOM Responsibilities
One of NAVSEASYSCOM's prime responsibilities
for ship maintenance is to administer SHIPALTs under
its technical control. NAVSEASYSCOM keeps informed of technical developments in its day-to-day
relations with the forces afloat, the naval shipyards,
private industry, and research centers. NAVSEASYSCOM may determine that a particular ship or class of
ships should be altered to bring them to a more efficient
and modem state of readiness. These alterations may be
changes to the hull, such as changes to bulkheads that
will strengthen bulkheads or changes to deck arrangements that will provide space for installation of
machinery; changes to machinery or substitution of
newer and more efficient machinery; changes to equipment, such as the replacement of an item with a more
efficient type; or changes in design. NAVSEASYSCOM
relies on input from the fleet and unit commanders for
the need of new SHIPALTs.
A repair is defined as the work necessary to restore
a ship or an article to serviceable condition without a
change in design, material, or in the number, location,
or relationship of parts. Repairs may be done by ship’s
force, tenders, ship repair facilities, or by naval or
civilian shipyards.
Before we discuss alterations, we need to understand that NAVSEASYSCOM may determine that some
work requested as an alteration may be better defined
as an alteration equivalent to repair. In that case,
NAVSEASYSCOM forwards the request to the
appropriate type commander (TYCOM) to be handled
as a repair. An alteration is considered to be an
alteration equivalent to a repair if it meets one or more
of the following conditions:
Commanding Officer Responsibilities
When the commanding officer of a ship believes a
SHIPALT is necessary, he/she sends a request to
NAVSEASYSCOM via the administrative chain of
command (3-M systems). Copies of the request are sent
to all ships of the type within the fleet for comments as
to the value of the SHIPALT for other ships of the
same type or class.
Materials that have previously been approved
for similar use and that are available from
standard stock are substituted without other
change in design.
Worn out or damaged parts, assemblies, or
equipment requiring renewal will be replaced
by those of a later and more efficient design
that have been previously approved.
INSURV Responsibilities
Parts that require repair or replacement to
improve reliability of the parts and of the unit
will be strengthened, provided no other change
in design is involved.
The reports of the Board of Inspection and Survey
(INSURV) are another source of recommended
SHIPALTs. When the board completes each material
inspection of a ship, it furnishes a list of recommended
repairs, alterations, and design changes that it feels
should be made. NAVSEASYSCOM normally will not
act on those recommendations until the commanding
officer of the inspected ship requests the changes, and
the TYCOM approves.
Equipment that requires no significant changes
in design or functioning but is considered
essential to prevent recurrence of unsatisfactory
conditions will be given minor modifications.
TY COM Responsibilities
This section deals only with ship alterations (SHIPALTs) as opposed to ordnance alterations (ORDALTs).
These are alterations to the hull, machinery, equipment,
or fittings that include a change in design, materials,
TYCOMs (or other administrative commanders)
must endorse all requests for SHIPALTs addressed to
NAVSEASYSCOM. Their endorsements must include
recommendations for or against approval, classification,
and applicability to other ships of the type. Copies of
the basic request and endorsements are forwarded to
other concerned TYCOMs with requests to comment on
them for the information of NAVSEASYSCOM.
activity. Only the authority granting the availability can
change the allotted period of time. However, a repair
activity may recommend a completion date to the
granting authority or request an extension of time to
complete work already underway. There are several
types of ship availabilities that we will define in the
next paragraphs. For example, restricted and technical
availabilities differ in whether the ship is or is not ready
to carry out its mission.
SHIPALTs fall into two broad categories: military
SHIPALTS and technical SHIPALTs. If there is a
question as to whether a proposed SHIPALT is military
or technical, NAVSEA will forward the proposal to
CNO for determination. You will most often install
technical SHIPALTs.
used to complete specific items of work in a
shipyard or SRF; the ship is NOT available to
perform its mission during that time.
changes the ship’s operational and military
characteristics and improves the ship’s
operational capabilities. Only CNO can approve
a military SHIPALT. An example of a military
SHIPALT would be the installation of a new
weapons system.
to complete specific items of work in a
shipyard or SRF; the ship IS available to
perform its mission during that time.
Other types of availabilities identify the type of
work to be done and where it will be done.
TECHNICAL SHIPALT—A technical SHIPALT is one that improves the safety of
personnel and equipment and/or improves
reliability, ease of maintenance, and efficiency
of equipment. A technical SHIPALT can only
be approved at the NAVSEA level.
A REGULAR OVERHAUL (ROH) AVAILABILITY is used to complete general repairs
and alterations in a naval shipyard or other
shore-based repair activity. The schedule for an
ROH for a given ship varies between 2 and 5
years according to an established cycle. An
overhaul can take as little as 2 months for small
ships and as much as 18 months for larger
ships. ROH planning begins about 18 months
before the scheduled overhaul.
Approved military and technical SHIPALTs are
ranked in order of priority on an annual basis in the
Amalgamated Military and Technical Improvement
Plan. The decision to install a SHIPALT is based on the
priority of the alteration in the Amalgamated Military
and Technical Improvement Plan, funding, ship
availability, and whether material is available to
complete the SHIPALT. When a decision is reached to
install a SHIPALT during a given fiscal year, the
alteration is entered into the Fleet Modernization
Program (FMP). Approved SHIPALTs are authorized
by letters issued not less than 180 days before the ship
is scheduled to begin overhaul or other types of repair
for repairs while the ship is underway. These
are emergency repairs that are necessary if the
ship is to continue on its mission, and they can
be done without changing the ship’s operating
schedule. These repairs will be done by the
ship’s force if possible, or if necessary, by
personnel from an IMA, SIMA, or SRF.
for general repairs and authorized alterations
that are not emergencies. This work is usually
beyond the capability of the ship’s force and is
normally scheduled in advance.
used to repair specific casualties and generally
takes first priority at a fleet IMA.
An availability is the period of time a ship is
assigned to undergo maintenance or repair by a repair
quite simple; others require planning so they can be
done during upkeep or overhaul periods.
for ship-to-shop work by the shore IMA,
tender, or repair ship. These availabilities are
usually scheduled to take place just before a
regular shipyard overhaul or restricted
A ship's effectiveness depends on its ability to
function well; therefore, ship’s personnel and IMAs
have a dual responsibility to keep it in prime condition.
That means that the ship's crew routinely handles
normal maintenance and repairs and IMAs handle those
repairs that a ship's crew cannot handle.
Repair activities are set up to do work the ship’s
forces cannot handle. Repair activities are IMAs,
XMAS, SRFs, and shipyards. The type of work and
available funds govern the assignment of repair work to
repair activities. The office of the Supervisor of
Shipbuilding (SUPSHIP) places and administers
contracts for the repair or overhaul of naval ships at
private shipyards, and contracts for civilian work to be
done in IMAs, SIMAs, and SRFs.
This section deals mostly with those jobs the ship's
crew cannot handle and which are done by repair
facilities. We will discuss what happens at an IMA or
SIMA. The following is a list of the different types of
repair facilities:
An intermediate maintenance activity (IMA) is
a repair ship (AR), destroyer tender (AD), or
submarine tender (AS).
Fleet and type commanders usually call on IMAs or
SIMAs to handle repairs and alterations under regular,
emergency, and concurrent availabilities. If work is
beyond an IMAs or SIMA’s capability, other activities
ashore, such as an SRF or a shipyard, will do it. In the
following paragraphs, we will discuss the work done by
the ship’s forces and IMAs. In addition, we will
examine the organization, duties of personnel, and QA
procedures used in an IMA.
A shore intermediate maintenance activity
(SIMA) is based on land and offers services
similar to those of an IMA.
A ship repair facility (SRF) is similar to a naval
shipyard but on a smaller scale and is usually
based outside the continental United States.
A shipyard is any full-service naval shipyard or
a civilian shipyard contracted for Navy work.
Each ship's force should be able to make its own
normal repairs. To do that, each ship should have the
necessary materials, repair parts, tools, and equipment.
The most competent and experienced personnel should
supervise these repairs. If ship's personnel are not
familiar with the needed repairs and tests, or cannot
handle a problem for any reason, the CO should request
an IMA or shipyard availability. Personnel who are not
familiar with these repairs and tests should take
advantage of an IMA or SIMA availability to observe
how such work is undertaken. If the ship's force needs
technical assistance, they should request it from the
local TYCOM's maintenance representatives.
While each type of IMA has its special purpose, all
of them have many characteristics and facilities in
common that make them suitable for general repair
work on most ships. Repair ships and tenders perform
battle and operational damage repairs on ships in the
forward areas, and they provide logistic support to ships
of the fleet. They also can provide other services,
including medical and dental treatment, for the ships
they tend. Their shops can handle hull, machinery,
electrical, and ordnance work, and they stock parts to
help them deal with most of the repairs they perform.
SIMAs are shore-based facilities that only do repair
work, while other departments on a shore base handle
the supply, medical, and administrative needs of the
ship. Ships are assigned to IMAs with a flexible
approach that considers unusual repair requirements and
operational commitments, particularly for ships outside
the continental United States.
The ship's force should follow a regular schedule of
preventive maintenance to be sure that equipment and
machinery are always ready for service. This includes
cleaning, inspections, operations, and tests to ensure
trouble-free operation and to detect faults before they
become major problems. Some inspections and tests are
IMA Availabilities
COMMANDING OFFICER.—The IMA's commanding officer has the overall responsibility for the
daily operation and function of the IMA as a whole.
The CO coordinates the activities of the IMA's
departments and divisions and is responsible to the
Ships are scheduled for regular IMA availabilities
or upkeep periods at certain intervals of time that vary
with different types of ships. There are numerous types
of availabilities used by TYCOMs and they vary
between the surface and submarine components.
Therefore, you should always refer to the governing
document associated with the command at which you
are stationed. The availability periods are usually
planned in advance and depend upon the quarterly
deployment schedule of each ship.
REPAIR OFFICER.—The repair officer is head of
the repair department on an IMA. The repair officer
oversees the upkeep, operation, and maintenance of the
equipment assigned to the repair department, and the
training, direction, and coordination of its personnel.
The repair officer keeps up with production and ensures
efficient and economical operation of the production
A ship's commanding officer sends a request for an
IMA availability with a forwarding letter to the
TYCOM or his or her representative. The request must
include job sequence numbers (JSNs) for work requests
in the Current Ship's Maintenance Project (CSMP) and
a listing of TYCOM master job catalogue work items.
repair officer assumes the repair officer’s responsibilities
in his/her absence and carries out the responsibilities the
repair officer delegates. This officer usually handles the
internal administration of the department and specifically keeps progress records on all work. In the submarine force, the assistant repair officer is called the
production management assistant (PMA).
A reviewing officer with TYCOM will review the
request and make any necessary corrections to conform
to established policies and procedures. Most of the
ship's work list items will be approved, but the ship
may have to furnish more detailed information on
certain work requests.
quality assurance officer (QAO) is responsible to the
commanding officer for planning, monitoring, and
executing the overall IMA QA program. The QAO
ensures that all work done by the IMA meets all
established technical and quality control requirements.
The reviewing officer will forward the approved
ship’s work requests to the appropriate IMA well in
advance of the period of availability so the IMA repair
department personnel can prepare for the work. Because
you should know something about these personnel
before you learn about the arrival conference, the shops,
and the ship maintenance procedures, we will discuss
them in the following paragraphs.
The planning and estimating (P & E) officer is
responsible to the assistant repair officer for planning
and estimating all work assigned to the IMA. The P &
E officer also is tasked with providing technical
information for repairs, preparing detailed work
packages for controlled work, and maintaining
specifications, standards, process instructions, and
Repair Personnel
Standard Organization and Regulations of the U.S.
Navy, OPNAVINST 3120.32, contains general
information about the relative positions and
responsibilities of IMA departments. These positions
may vary between the submarine and surface
components, but their responsibilities are generally the
same. Also, TYCOMs issue standard ship organizations
for their type that describe the organization for every
routine function and most emergency conditions that
can exist aboard ship. The following paragraphs explain
the roles of the repair officer, the assistant repair
officer, quality assurance officer, planning and
estimating officer, repair division officers, diving and
salvage officer, and enlisted personnel.
DIVISION OFFICERS.—The division officers
(DOs) have both administrative and production
responsibilities for the actual work that is done in shops
under their supervision. They have administrative and
production responsibility. Their administrative
responsibility is in the administration of personnel in
their respective divisions, including the assignment of
berths and watches, and all training and training
records. Their production responsibilities include
oversight of all work requests and review of progress,
requisitions for material, proper operation of division
be accepted or rejected by the IMA or deferred to a
future IMA availability, depending on shop loading and
material availability. Before the AWR is accepted,
rejected, or deferred, it will be ship checked by the lead
and assist work centers for applicability. If the AWR is
accepted for work in the current availability, it will be
checked by the P & E and QA divisions for technical
and QA requirements and then issued to the shop.
Remember, this is a general overview of the work
request routing from the customer to the craftsman, and
each IMA has different routing sequences as established
shops for which they are responsible, safety, and
progress reports to the repair officer.
position of diving and salvage officer may be a separate
assignment or a collateral duty for an officer in the
repair department. In either case, the diving and salvage
officer is responsible for the supervision of all diving
operations, the maintenance of diving and salvage
equipment, and compliance with diving instructions and
ENLISTED PERSONNEL.—Navy enlisted personnel provide the technical skills required aboard
IMAs. The Manual of Navy Enlisted Manpower and
Personnel Classifcations and Occupational Standards,
NAVPERS 18068, contains detailed information on the
enlisted rating structure.
Ship/IMA Work Coordination
Ship’s engineering personnel must know the status
of work underway during an IMA availability whether
that work is being done by the ship’s force or the IMA.
You need this information to coordinate your own work
with that being done by the ship’s force. There are three
basic kinds of work that require coordination: (1)
equipment removed by the ship’s force to be delivered
to the IMA for repair, (2) equipment dismantled by the
ship’s crew so they can send parts to the IMA for repair
(also known as ship-to-shop jobs), and (3) repairs the
IMA force makes on the ship.
Arrival Conference
An arrival conference is usually held immediately
when a ship begins an IMA availability or an upkeep
period. Representatives of the ship, the repair
department, and the TYCOM usually attend the
conference. They discuss the relative needs of the ship
and the urgency of each job and approve/disapprove
work requests, clarify uncertainties, and arrange for
temporary services such as electricity and steam.
The IMA usually appoints a ship superintendent,
normally a chief petty officer, who should always know
the status of all jobs on the ship and on the IMA. The
ship will also normally appoint a chief petty officer for
that purpose to interface with the IMA. The person(s)
in these positions are a liaison between the ship and the
IMA for all work in progress and completed, and all
tests required and completed. They should keep a daily
running progress report of each job and should report
that information daily to the ship’s/IMA representative.
Work Requests
This section will briefly discuss the routing of the
work request from the time the ship submits the ship’s
maintenance request action form (OPNAVINST
4790/2K) until you receive it to begin work.
As mentioned earlier, the ship will submit a
4790/2K to the TYCOM requesting specific maintenance work to be accomplished. The 2K is screened
at the TYCOM level for completeness and to determine
what type of repair facility to assign the maintenance
action to. If the IMA is assigned the maintenance
action, the 2K is routed to the Maintenance Document
Control Office (MDCO) and the automated data
processing (ADP) facility for processing. MDCO and
ADP will process the 2K, entering it onto the CSMP
and will issue an automated work request (AWR) (fig.
2-1) to the IMA.
Repair Department
You need a general idea of the shops composing
the repair department and their functions whether you
are assigned to an IMA or are part of a ship’s company.
In this section, we will describe the shops as they are
organized in the divisions on a destroyer tender (AD),
which is representative of all surface IMAs.
Submarine-related IMAs are organized differently but
have the same capabilities.
repair division consists of the shipfitter shop, sheet
metal shop, pipe and copper shop, weld shop, carpenter
shop, diving locker, and canvas shop. As an HT, you
When the AWR arrives at the IMA, it is screened
by the RO for applicability, shop capability, urgency,
and manning requirements. At this point, the AWR may
Figure 2-1.—Automated Work Request.
will probably be assigned to at least a tour of duty as a
member of R-l division. We will explain the duties of
personnel assigned to each of these shops in the following paragraphs. On submarine tenders, the carpenter
shop, dive locker, and canvas shops are assigned to R-6
machinery repair division consists of the inside machine
shop, the outside machine shop, the boiler shop, and the
foundry shop. We will explain the duties of personnel
assigned to each of these shops in the following
Shipfitter Shop.—Personnel make repairs on the
hull, manufacture and install various structural metal
components, repair or replace watertight fixtures, and
handle alterations designated for forces afloat.
Inside Machine Shop.—Personnel repair or
fabricate mechanical parts that require work done on
machine shop tools and equipment. They do metal
plating and engraving, and they test metals to determine
their characteristics. They also handle alterations
designated for forces afloat.
Sheet Metal Shop.—Personnel make all types of
repairs and fabrications on light gauge sheet metal and
handle alterations designated for forces afloat.
Outside Machine Shop.—Personnel shop test and
repair all types of machinery used in naval ships. They
also handle alterations designated for forces afloat. On
submarine tenders, they are assigned to R-9 division.
Pipe and Copper Shop.—Personnel fabricate and
repair most pipe and tubing, test completed work
hydrostatically, and handle alterations designated for
forces afloat.
Boiler Shop.—Personnel shop test, inspect, and
repair boilers of naval ships.
Weld Shop.—Personnel weld most metals, including high-pressure welding on boilers. They repair
castings, stress relieve castings and forgings, forge
special tools and hull fittings, and case harden
low-carbon steel.
Foundry Shop.—Personnel pour castings of various
metals to produce repair parts and whole items used on
the ship. On submarine tenders, they are assigned to
R-6 division.
electrical repair division consists of the electric shop,
the gyro shop, the printing shop, and the photo shop.
NOTE: The nondestructive testing laboratory
performs all nondestructive testing used to test the
quality of the welds and is part of the quality control
division, R-8.
Electric Shop.—Personnel inspect, test, repair, and
make adjustments to nearly all electrical equipment, and
they also handle electrical alterations designated for
forces afloat. (On submarine tenders, the print and
photo shops are assigned to R-O division.)
Carpenter Shop.—Personnel repair and fabricate
most items made of wood, and lay linoleum tile,
magnetite, and terrazzo covers on decks. The pattern
shop functions under the carpenter shop and fabricates
patterns of wood, metal, and plastic for templates and
foundry castings.
The electronics repair division consists of the
electronics shop and the calibration shop.
Canvas Shop.—Personnel fabricate miscellaneous
canvas covers, awnings, and boat cloths, and they repair
furniture using leather and cloth fabrics.
Electronics Shop.—Personnel align and repair all
types of electronic equipment, make field changes, and
maintain an electronics publications library.
Diving Locker.—Personnel inspect the underwater
portion of the hull and prepare the underwater hull
reports for the repair officer. They also replace
propellers on destroyers and small ships and repair or
replace other items underwater as needed. They clean
propellers, sonar domes, sea chests, and large injection
valves; clear fouled propellers and sea chests; and
maintain the diving boat and diving equipment in repair
and operational readiness.
Calibration Shop.—Personnel repair and calibrate
most test equipment used on naval ships.
As an HT, most repairs that you will make require
a great deal of quality controls to ensure that the system
Eliminate unnecessary man-hour and dollar
you are working on is restored to its original conditions.
The QA program provides a uniform policy of
maintenance and repair on ships and submarines. It
improves discipline in the repair of equipment, safety of
personnel, and configuration control. It is essentially a
program to ensure that all work meets specifications or
that any departure from specifications is approved and
documented. You, the supervisor or craftsman, are
expected to carry out the QA program. This section will
give you the broad knowledge you need to understand
how it works.
Improve the training, work habits, and
procedures of maintenance personnel.
Store, locate, and distribute required technical
information more effectively.
Plan realistic material and equipment/
maintenance tasks.
The ever-increasing technical complexity of
present-day surface ships and submarines has pointed to
a need for special administrative and technical procedures known collectively as the QA program. The
fundamental QA concept is that all maintenance personnel have the responsibility to prevent defects from the
beginning to the end of each maintenance operation.
You must consider QA requirements whenever you plan
maintenance, and you must apply the fundamental
The Navy’s fleet commanders in chief (CINCs)
publish and update QA manuals that set forth minimum
QA requirements for both the surface fleets and the
submarine force. The TYCOMs then publish QA
manuals that apply to their forces but are based on the
fleet CINC manuals. Since these CINC and TYCOM
manuals apply to a wide range of ship types,
equipment, and resources, the instructions are general in
nature. Therefore, each activity must implement its own
QA program that meets the intent of the latest versions
of the fleet CINC and TYCOM QA manuals. If higher
authority imposes more stringent requirements, they will
take precedence.
Quality control (QC) means you regulate events
rather than being regulated by them. It means that you
work with proper methods, material, and tools. In other
words, knowledge is the key, and knowledge comes
from factual information.
The Navy’s QA program applies to maintenance
done aboard ship by the ship’s force, in IMAs, SIMAs,
SRFs, and shipyards. However, this section will
concentrate on QA work done by the ship’s force and
IMAs since you may be assigned to either type of duty.
The QA program provides a way to document and
maintain information on the key characteristics of
equipment. It helps you base decisions on facts rather
than intuition or memory. It provides comparative data
that will be useful long after you have forgotten the
details of a particular time or event. You can get
knowledge from data, ship's drawings, technical
manuals, material references (such as APLs), and many
other sources. As you use these sources, you will
develop the special skills you need to analyze
information and supervise QA programs.
The basic thrust of the QA program is to ensure
that you comply with technical specifications during all
work on ships of both the surface fleet and the
submarine force. The key elements of the QA program
include administrative and job execution components.
The administrative component includes the requirement
to train and qualify personnel, monitor and audit
programs, and complete the QA forms and records. The
job execution component includes the requirement to
prepare work procedures, meet controlled material
requirements, requisition and receive material, conduct
in-process control of fabrication and repairs, test and
recertify equipment, and document any departure from
A good QA program provides enough information
so you can accomplish the following goals:
Improve the quality, uniformity, and reliability
of the total maintenance effort.
Improve the work environment, tools, and
equipment used in maintenance.
The Navy has a long-standing requirement that
maintenance work must meet technical specifications.
The person performing the maintenance is ultimately
responsible for ensuring that this requirement is met.
Therefore, any worker who is expected to do the job
properly must be properly trained, provided with correct
tools and parts, familiar with the technical manuals and
plans, and adequately supervised.
The CO cannot maintain high standards of quality
workmanship by merely creating a QA organization
within a maintenance organization. The organization
must have the full support of everyone within it. It is
not the inspection instruments and instructions that
bring high standards of quality; it is the attitudes of
those who do the work.
The Quality Assurance Officer
The QAO is responsible to the CO for the
organization, administration, and execution of the ship’s
QA program according to the QA manual. On most
surface ships other than IMAs, the QAO is the chief
engineer with a senior chief petty officer assigned as
the QA coordinator. The QAO is responsible for the
These elements continue to be the primary means of
assuring that maintenance is performed correctly.
Once there is a decision to proceed with
maintenance, you must apply QA requirements at the
same time you plan the maintenance and supervise its
completion. Technical specifications will come from a
variety of sources. The determination of which sources
are applicable to the particular job will be the most
difficult part of your planning effort. Once you decide,
the maintenance objective becomes two-fold: (1) ensure
the maintenance work meets all specifications, and (2)
ensure the documentation is complete and accurate and
can be audited.
— Coordinating the QA training program as an
integral part of the ship's/IMA's overall training
— Maintaining the ship’s/IMAs QA records and
test and inspection reports
— Maintaining departure-from-specifications records that can be audited
— Reviewing procedures and controlled work
packages prepared by the ship/IMA
The Navy's QA program organization begins with
the fleet CINCs, who provide the basic QA program
organization responsibilities and guidelines. The
TYCOMs provide instruction, policy, and overall
direction to implement and operate the force QA
program. Each TYCOM has a force QA officer
assigned to administer the force QA program.
Commanding officers are responsible to the TYCOM,
via the chain of command, for QA of their organization.
The CO is responsible for organizing and implementing
a QA program within the organization to carry out the
provisions of the TYCOM's QA manual, and assigns
key QA personnel for that purpose. In most cases, it is
a collateral duty assignment for these key personnel on
ships and a primary duty for key personnel at IMAs.
The following paragraphs will give you a brief
description of the responsibilities of each of these
positions followed by a discussion of their training and
— Conducting QA audits as required and
following up on corrective action to ensure
compliance with the QA program
— Preparing QA/QC reports as required by higher
— Qualifying key personnel in the QA program.
The Division Officer
The DOs ensure that all division personnel receive
the necessary QA training and qualifications for their
positions and that they carry out their QA
The Commanding Officer
The Quality Assurance Coordinator
The CO is responsible for the quality of material
within a command, and he/she depends on the full
cooperation of all hands to help meet this responsibility.
The quality assurance coordinators (QACs) are
senior petty officers assigned to this duty. Personnel
assigned to this duty train other QA personnel, conduct
interviews for prospective QA personnel, and administer
written examinations for QA qualifications.
the material and workmanship for that stage of
Ship Quality Control Inspector
Personnel who serve as SQCIs will be responsible
for the following:
If you are a work center supervisor, you will most
often be appointed and trained in the collateral duty of
ship quality control inspector (SQCI). IMAs have
personnel permanently assigned to these positions
within the QA division. As an SQCI, you will be
deeply and directly involved in QA. You must be
familiar with all aspects of the QA program and the QC
procedures and requirements of your specialty. As an
SQCI, you should act as an inspector or assign a
collateral duty inspector at the same time you assign
work to be sure the work is inspected in progress and
on completion. Do not allow personnel in your shop to
do a final inspection on their own work.
Developing a thorough understanding of the
QA program.
Training all work center personnel until they
are familiar with the QA/QC requirements that
apply to your work.
Ensuring that all controlled work done by your
work center personnel meets the minimum
requirements in the latest plans, directives, and
specifications of higher authority and that
controlled work packages (CWPs) are properly
used on repair work.
Inspections normally fall into one of the following
three inspection areas:
Inspecting all controlled work for conformance
to specifications and witnessing and
documenting all tests required on these systems.
RECEIVING OR SCREENING INSPECTIONS. These inspections apply to material,
components, parts, equipment, logs and records,
and documents. They determine the condition
of material, proper identification, maintenance
requirements, disposition, and correctness of
related records and documents.
Maintaining records and files to support the QA
program and ensuring the QA manual is
Ensuring test personnel use measuring devices,
instruments, inspection tools, gauges, or fixtures
that have current calibration stickers or records
when acceptance tests are performed.
IN-PROCESS INSPECTIONS. These inspections are specific QA actions that are required
in cases where you cannot know whether the
job was done right without the inspections.
They include witnessing, application of torque,
functional testing, adjusting, assembling, servicing, and installation.
Ensuring a qualified inspector accepts the work
before the ship installs the product when an
inspection is beyond the capability of the
ship’s/IMA's QA inspector.
FINAL INSPECTIONS. These inspections
comprise specific QA actions performed
following the completion of a task or a series
of tasks. An example is an inspection of work
areas after several personnel have completed
Reporting all deficiencies to the ship’s QAC
and keeping the division officer informed.
Helping the DO and QAO conduct internal
audits and correct discrepancies.
Work Center Controlled
Material Petty Officer
Most commands that have a QA program will issue
you a special ID number that will identify you as a
qualified SQCI. In addition, the QAO will assign a
personal serial number to each shop SQCI as proof of
certification to use on all forms and tags that require
initials as proof that certified tests and inspections were
made. This will provide documented proof and
traceability to show that each item or lot of items meets
If you supervise a work center that has level I or
subsafe material, you must ensure the procedures that
govern controlled material are followed. Your work
center or division will usually appoint a controlled
material petty officer (CMPO) to handle these
responsibilities. After training, that person will inspect,
segregate, stow, and issue controlled material in the
work center.
As an HT, you may be required to organize and
supervise an HT shop aboard ship or at a shore facility.
It will be your responsibility to supervise and instruct
personnel of lower rates in the techniques of carpentry
and woodworking, plate and sheet metal layout and
fabrication, pipefitting, and the welding of various types
of metals. In addition, you will be required to estimate
the time, materials, and personnel required for the
completion of various wood and metalworking jobs; to
maintain the HT shop, including all tools and
equipment, in the best possible condition; and to ensure
that all safety precautions are observed by your
personnel. To supervise HT shop work efficiently,
afloat or ashore, you will rely mostly upon your past
experience in shop work and repair procedures.
Shop Craftsmen
Shop craftsmen are not normally trained in specific
QA functions as are the key QA people. Still, they must
do their work under QA guidelines if they apply. They
will work closely with their shop supervisors and QA
inspectors to ensure the work is done according to QA
guidelines and procedures.
As an HT, you will be required to document the
repair work that you do on any ship’s system. This
documentation is done in an approved and issued CWP
received from the P & E division. The CWP provides
QC requirements and procedures to help ensure that
fabrication or repair will produce a quality product.
These requirements or procedures include both TYCOM
and local command-generated information for work
package processing and sign-off. The typical CWP will
have QA forms, production task control forms,
departure from specifications forms, material deficiency
forms, QC personnel sign-off requirements, and hydro
or test forms. Each CWP covers the entire scope of the
work process and is a permanent and legal record of the
performed work. The job control number (JCN)
provides traceability from the work package to other
certification documentation. When filled in, the CWP
documents adherence to specified quality standards.
The purpose of this section is to acquaint an HT
with some of the most important things that must be
considered by a person in charge of a work center. It is
impossible, however, to cover all the procedures and
problems that arise in the daily operations of a work
center. By studying this section of the chapter, you will
become aware of some of the things that occur,
particularly in regard to the job of setting up shop
procedures and the methods by which everyday
problems are solved.
Leading petty officers, especially those who are in
direct contact with personnel, often fail to recognize
that they are part of the ship’s administrative organization. Every petty officer in the shipboard organization
is definitely part of the administrative group. In such a
capacity, you have many responsibilities that you are
expected to carry out by interpreting and executing the
established policies and procedures. Supervisors can
accomplish this properly only when they have a clear
understanding of these policies and procedures, as well
as their place within the command’s organization.
You must ensure that the CWP is at the job site
during the performance of the task. Since the CWP is
the controlling documentation for the performance of
any repair work you accomplish, it is required on the
work site to ensure that no steps or inspection are
omitted. If the work procedure requires the
simultaneous performance of procedure steps and these
steps are done in different locations, use locally
developed practices to ensure you maintain control for
each step.
As a supervisor, the petty officer is expected to spot
operating difficulties in their shop and do something
about them. You must have an understanding of your
department, ship’s organization, and the proper channels
and lines of authority which are open to you. The
further up the organizational chain that you progress,
the greater your responsibilities become. The job of a
supervisor is a detailed one, and most important with
respect to the operation of any naval repair activity or
facility. A weakness in the performance of any supervisory duty or responsibility reduces the effectiveness of
the work center as a whole.
Immediately after a job is completed, each assigned
work center and the QAO will review the CWP
documentation to be sure it is complete and correct. If
you and your workers have been doing the assigned
steps as stated, this should not be a problem. Be sure all
verification signature blocks are signed. Make sure all
references, such as technical manuals or drawings, are
returned to the appropriate place.
Checking and inspecting completed repairs or
replacement parts
Obviously, then, the HT in charge of an HT shop
should fully appreciate and understand the responsibility
he/she holds as a member of a shipboard organization,
and be able to identify each of his/her duties with
respect to any assigned job. This is not an easy task in
a field so complex and variable as the work of a shop
Promoting teamwork
From the extent of the preceding list it is obvious
that the job of a supervisor covers a broad field. These
items are quite general in nature; therefore, it is
necessary for each HT shop supervisor to carry out a
detailed study of his/her own specific duties and
Some administrative personnel have made long lists
of the responsibilities of shop supervisors. A close
examination of such lists might disclose to each leading
petty officer points of differences as well as points of
agreement. Many differences are of minor importance,
and others represent major differences in responsibilities. After such a comparison, it might be concluded
that an accurate list of duties for any given job can be
made only by the individual occupying the particular
job. The following list includes the duties and responsibilities that are common to most shop supervisors:
The leading petty officer in charge of an HT shop
should take advantage of every opportunity to provide
personnel with specific information about their jobs.
The type of petty officer who says, “Never mind why;
just do as you are told,” is rapidly being replaced by
the supervisor who recognizes the importance of each
Keeping personnel satisfied and happy on the
As the leading petty officer in charge of an HT
shop, you should use all possible interest factors. You
should study each of your personnel and use those
interest factors that seem to obtain the best results
according to individual characteristics. Your ability to
interest your personnel in their work is important, as it
determines your success or failure as a supervisor. Your
proficiency in rating depends in part on the quality and
quantity of work assigned personnel produce, which, in
turn, reflects the morale of the shop personnel and their
interest in their work.
Adjusting individual grievances
Maintaining discipline
Careful planning is necessary to keep an HT shop
running efficiently and productively. Remember that
any time lost, whether on a job or between jobs, lowers
the overall efficiency of the shop. To keep the work
flowing smoothly, you will have to consider such
factors as sizing up the job, checking on the availability
of materials and supplies, time and material
requirements, allowing for priority of work, assigning
work, checking the progress of the work, and checking
the completed work.
Getting the right person on the right job at the
right time
Using tools and materials as economically as
Preventing conditions that might cause
Keeping records and making reports
Maintaining the quality and quantity of repair
Planning and scheduling repair work
Training personnel
Sizing up the Job
Requisitioning tools, equipment, and materials
When a new job order comes into the HT shop,
check it over carefully to be sure that it contains all the
necessary information. Don't start a job until you are
sure that you understand in detail the scope of the job.
If blueprints or drawings will be needed, check to be
sure that they are available. Shipcheck each job as soon
Inspecting and maintaining tools and equipment
Giving orders and directions
Cooperating with others
as possible to verify the scope of the job against
available blueprints or other technical documentation.
course, be added to the total estimate of time required
to complete the job.
Checking on Materials
3. Find out what materials will be required, and
make sure they are available. If the specified materials
are not available, time may be lost while you try to find
a satisfactory substitute.
Before starting a job, be sure that all the required
materials will be available. This means not only the
correct kind of wood or metal for the job, but also
whatever other materials may be required to finish the
job, such as glue, dowels, nails, welding rod, rivets,
bolts, clips, and hinges. Ensure that all material used for
the repair meets applicable specifications and are
4. Find out what part of the job (if any) must be
done in other shops. It is important to consider not only
the time actually required by these other shops, but also
the time that may be lost if one of the shops holds up
the work of your shop. Never attempt to estimate the
time that will be required by other shops. Each shop
must make a separate estimate, and these estimates must
be combined to obtain the final estimate.
Estimating Time for a Job
Accuracy in estimating the required time for a
specific job is primarily a matter of experience. When
making a time estimate, you will compare the present
problem with one you have solved in the past. An
estimate, in a very real sense, is a guess, but it is an
intelligent guess when based on the proper use of
records and experience.
5. Consider all the interruptions that might cause
delay, over and above the time actually required for the
work itself. Such things as ship's drills, inspections,
field days, and working parties will affect the number
of personnel that will be available to work on the job at
any given time.
6. Next, try to estimate the time that will be
required for the work itself. Perhaps the best way to do
this is to divide the total job into its various phases or
steps that will have to be done. The time required for
each step depends partly on the nature of the job and
partly on the number of personnel available. You may
find it helpful to draw a diagram or chart showing how
many persons can be assigned to each step of the job,
and how long each step is likely to take. Figure 2-2
shows a chart made up to estimate the total time
required to make certain repairs to a gangway.
From time to time, you will probably be called
upon to give the estimate of the time that will be
needed to complete a repair job. For most of the routine
jobs coming into the HT shop, a quick estimate made
on the basis of your experience will probably be
sufficient. For urgent jobs, however, the time required
for completion may be an important consideration; and
you should be very cautious in making these estimates.
The estimate(s) that you make may have an effect on
the operational schedule of a ship; therefore, it is
important to consider all factors that might affect the
time required for the job.
The total job is divided up into nine phases or
The following steps are generally required to make
an accurate estimate of the time that will be required
for a repair job.
A. Making the template. This step might take one
person about 1 hour.
1. Study the job order and any blueprints or other
drawings that are applicable to determine the extent of
the job. For a repair job, inspect the damaged item to
determine whether or not it requires repairs or
replacements in addition to those specified in the job
order. In other words, the first thing to do is to get all
possible information about the job.
B. Obtaining metal fittings (treads and padeyes).
This step might take one person about 1 hour.
C. Renewing one stringer and six treads. This step
might take four people about 6 hours.
D. Sanding the surface and using wood filler. This
step might take two people about 2 hours.
2. Find out the priority of the job. If it has a lower
priority than some of the work already scheduled to be
done in the shop, you will not be able to start work
immediately. Any delay in starting the job must, of
E. Giving the first coat of varnish. This step might
take one person about 1 hour.
Figure 2-2.—Estimating time required for a gangway repair job.
F. Drying time (8 hours). This must be counted in
the total estimate even though no work can be
done on the gangway during this period.
24 man-hours
4 man-hours
G. Giving the second coat of varnish. This step
might take one person about 1 hour.
1 man-hour
0 man-hour
1 man-hour
0 man-hour
1 man-hour
H. Drying time (8 hours).
I. Putting on the metal fittings. This step might
take one person about 1 hour.
Notice that, although there are four people available
to work on this job, it is not possible for all four to be
working on it at all times. Most of the work must be
done in sequence; for example, you can’t finish the
surface before you have renewed the stringer and treads,
and you can‘t make the new stringer and treads before
you have made the template. Step A (obtaining the
metal fittings) could be performed at any convenient
time before step I (putting on the metal fittings). The
advantage of using a diagram such as the one shown in
figure 2-2 is that it shows at a glance the total number
of hours that must be allowed for the work-in this
case, 28 hours.
1 man-hour
1 man-hour
33 man-hours
So you find that the total job requires 33 man-hours
of work. But what does this mean? Does the number of
man-hours tell you how long the job is going to take?
Is it safe to assume that a job requiring 33 man-hours
can be done in 8 1/4 hours if you put four people to
work on it? Obviously not, since there is a limit to the
number of people who can work on the job at any
given time.
The unit MAN-HOURS, then, is a measure of
amount of work but not of total length of time. You
should be very cautious about using man-hours when
estimating how long a job will take, since this measure
does not allow for the sequence in which the work must
be performed, the number of steps required, or the
number of people who can work on the job at each
The diagram shows you something else, too: the
number of man-hours required for each step. Let’s add
these up:
base times the height (π R H. For example, to compute
the weight of the 2 1/2-inch extra strong steel pipe
shown in figure 2-3, you would use the following
Material Estimates
The material you will use on a given job will be
determined from specifications or plans. If the material
is not specified, you will decide what you need and
select it. Your decision will be based on the purpose of
the structure or object, and the conditions that it will
meet in service. Some of the “in-service conditions” are
resistance to corrosion, resistance to acids, or resistance
to wear. You will have to consider the weight to be
supported, pressures to be withstood, and working
stresses that may be encountered. Safety, too, is an
important point to consider in determining the material
to use on a particular job. There is no set rule to follow. Each problem must be considered individually.
Step 1. Compute the volume of metal contained in
cylinder 1, using the formula volume = πR H.
Substituting known values we find that:
π = 3.1416
R = 1.4375
H = 30 ft (360 inches)
V = 3.1416 (1.4375)2360
ALLOWING FOR WASTE.—In most jobs, a
careful study of the detail plans will reveal the exact
amount of material needed for a particular installation
or repair. However, it is sometimes impossible to use
every linear foot of a length of pipe or bar stock or to
use every square foot of plate or sheet metal. Some
waste is unavoidable, and an allowance for such waste
is necessary in material estimates.
V = 2337.0 cu in.
Step 2. Compute the volume of metal contained in
cylinder 2:
π = 3.1416
R = 1.1615
WEIGHT CONSIDERATIONS.—Weight considerations are important in shipboard repairs and alterations. Consequently, it not only may be necessary for
you to determine the amount of material required for a
job, but also to calculate the weight of the material
going into the job. The weight of pipes, tubes, plates,
sheets, and bars can be determined in either of two
ways: (1) by referring to tables in a handbook and
locating the weight per linear or square foot of the
particular material in question; and (2) by arithmetical
computation. For example, suppose you need to know
the weight of a 30-foot length of 2 1/2-inch extra strong
steel pipe. By referring to the appropriate table in a
piping handbook, we find that this pipe weighs
approximately 7.66 pounds per linear foot. Thus, a
30-foot length weighs 229.8 pounds.
H = 30 ft (360 inches)
V = 3.1416 (1.1615)2360
V = 1525.7 cu in.
But, suppose you do not have such tabulated
information available. In that case, it is necessary to
determine the volume of metal involved and multiply
that result by the weight of the metal per cubic inch. To
compute the volume of metal in a pipe or tube, think of
it as being two cylinders. The outside diameter being
cylinder 1 and the inside diameter being cylinder 2. The
result obtained by subtracting the volume of cylinder 2
from the volume of cylinder 1 will be the volume of
metal (in cubic inches) contained in the pipe or tube.
The volume of a cylinder is equal to the area of the
Figure 2-3.—Actual measurements of inside and outside
diameters of 2 1/2-inch extra strong steel pipe.
Step 3. Find the volume of metal contained in the
pipe by subtracting the volume of cylinder 2 from the
volume of cylinder 1:
Table 2-2.—Weight of Various Gauges of Uncoated Plain
Steel Sheet Metal
2337.0 - 1525.7 = 811.3 cu in.
Step 4. Find the weight of the pipe by multiplying
the volume of metal by the weight of steel, shown in
table 2-1:
811.3 × 0.284 = 230.4 lb
The weight of plate and sheet metal structures may
be found by computing the volume of metal contained
(in cubic inches), and then multiplying the volume by
the weight of the metal (per cubic inch), as shown in
table 2-2. As an example, find the weight of a steel
plate that is 68 inches in length, 44 inches wide and 1/2
inch thick. Using the formula weight = volume ×
weight of the metal per cubic inch, we use the
following procedure:
Step 1. Compute the volume of metal contained.
The weight of steel per square foot may be
determined by multiplying the thickness of the metal by
40.9. Table 2-2 lists the weight per square foot of the
various gauges of uncoated plain steel sheet metal, and
also the decimal equivalents of the different gauges.
Volume = length × width × thickness
V = 68 × 44 × 1/2
V = 1496 cu in.
Obviously, to calculate the weight of a particular
structure, you must be able to break the whole down
into its component geometrical parts, circles, squares,
rectangles, pyramids, and so on, and determine their
respective volumes. Further, you need to know the
weight of metal per cubic inch. This information can be
found in a variety of handbooks readily available in the
engineer or repair department office. Table 2-1 gives
the information for a few of the more common metals.
Step 2. Find the weight of the steel plate.
Weight = volume of metal × weight per cu in.
W = 1496 × 0.284
W = 424.86 lb
When specific job requirements are known,
estimating of material needed is no problem. However,
when estimating requirements for future use, you will
have to anticipate your needs. Referring to records of
previous jobs and records of materials expended can
help eliminate much guesswork.
Table 2-1.—Weight of Common Metals
Priority of Work
In scheduling work in an HT shop, you will have to
consider the priority of each job. Most job orders will
have a ROUTINE priority; this means that they must be
done as soon as possible, within the normal capacity of
the shop. Jobs having an URGENT priority must be
working party. At that time, however, you probably did
not understand “how” or “why” the stores were placed
aboard. As a HTI or HTC, you are expected to know
the immediate supply channels in order to obtain the
material you need. The fact that there are supply
specialists aboard does not relieve you of the
responsibility for aiding in procuring, handling, stowing,
and accounting for the materials used in your shop.
done immediately, even at the expense of routine jobs
that may be in progress. Jobs with a DEFERRED
priority do not constitute a problem, since they are
usually accomplished when the workload of the shop is
light and there are no routine or urgent jobs to be done.
Assigning Work
The assignment of work in the HT shop is
extremely important. As a rule, the more complicated
jobs should be assigned to the more experienced
personnel. When time and the workload of the shop
permit, however, the less experienced personnel should
be given difficult work to do under proper supervision
so that they may acquire skill and self-confidence.
The big job of supply is handled by the supply
department. But if that department does not know what
you need, you are not going to have the material you
want when you need it. It is your responsibility to keep
the proper people informed of your estimated needs so
that you will have the required materials on board at all
times. Most of your orders will be placed through your
division officer or the head of the department, but in
some cases, you may order directly from the supply
When assigning work, be sure that the person who
is going to do the job is given as much information as
necessary. An experienced person may need only a
drawing and a general statement concerning the finished
product. A less experienced person will probably
require additional instructions concerning the layout of
the job and the procedures to be followed.
Selecting Materials and Repair Parts
The materials and repair parts to be used are
specified for many jobs, but not for all. When materials
or parts are not identified in the instructions
accompanying the job, you will have to use your own
judgment or do some research to find out just what
material or part should be used. When you must make
the decision yourself, select the material on the basis of
the purpose of the structure or part and the service
conditions it must withstand. Operating pressure and
operating temperature must be considered in selecting
materials. For some applications, wear resistance or
corrosion resistance will be important; for others (as, for
example, for high-temperature steam piping), creep
resistance will be a necessary property of the material.
Checking Progress of Work
When you are in charge of the HT shop, you will
have to keep a constant check on the progress of all
work. In particular, be sure that the proper materials are
being used, that the work is set up properly, that
personnel are using the correct tools properly, and that
all safety precautions are being observed. Note the
progress of each job in relation to the planned schedule
of work; you will probably find that some jobs are
ahead of schedule, while others are lagging behind. If
necessary, reschedule the work to prevent the
development of bottlenecks. By frequently talking to
shop personnel and answering their questions, you can
prevent jobs from being spoiled, as might happen if you
were not available to give correct details on the jobs.
The shipboard sources of information that will be
helpful to you in identifying or selecting materials and
repair parts include (1) nameplates on the equipment,
(2) manufacturers’ technical manuals and catalogs, (3)
stock cards maintained by the supply officer, (4)
specifications for ships, (5) ship's plans, blueprints, and
other drawings, and (6) allowance lists.
Checking Completed Work
When you are in charge of the HT shop, it will be
your responsibility to inspect and approve all finished
work before it is allowed to leave the shop. In addition,
you must make sure that all shop records concerning
finished work are complete, correct, and up to date.
NAMEPLATES on equipment supply information
regarding the characteristics of the equipment, and are
therefore a useful source of information concerning the
equipment itself. Nameplate data seldom, if ever,
include the exact materials required for repairs;
however, the information given on the characteristics of
the equipment may be a useful guide for the selection
of materials.
In all probability, your first experience with naval
supplies and repair parts was as a member of a store's
are furnished with practically all machinery and
equipment on board ship. Materials and repair parts are
sometimes described in the text of these technical
manuals; usually, details of materials and parts are
given on the drawings. Manufacturers’ catalogs of repair
parts are sometimes furnished with shipboard
The set of STOCK CARDS that is maintained by
the supply officer is often a valuable source of
information for the identification of repair materials and
repair parts. One of these cards is maintained for each
machinery repair part carried on board.
SHIP'S PLANS, BLUEPRINTS, and other drawings
available on board ship are excellent sources of
information on materials and parts to be used in making
various repairs. Many of these plans and blueprints are
furnished in regular large sizes; some drawings are
being furnished on microfilm to naval shipyards and to
repair ships and tenders.
Handling Materials and Equipment
Figure 2-4.—Clamp for handling heavy plate.
As an HT, your duties will include the supervision
of the handling, stowing, and inventory of all shop
materials and repair parts. The rigging and actual
transferring of the materials, parts, and equipment to
your ship will be done under the supervision of the
Boatswain’s Mate. It is your responsibility to furnish the
personnel and supervise the stowage of the materials or
equipment in the proper shop stowage space.
Heavy plate is usually handled with wire rope slings
or straps or with an approved-plate clamp such as the
one shown in figure 2-4. These clamps should NOT be
used for handling bundles of sheet metal, since the
sheets in the middle could slip and cause the entire load
to drop. Bulky items such as bars, strap, and structural
shapes are usually handled with slings or straps. The
chokers shown in figure 2-5 are effective devices for
handling pipe and other materials that must be gripped
tightly; when the hooks are used in pairs, the pull
should be from opposite sides of the load, as shown in
figure 2-5.
Figure 2-5.—Chokers for handling pipe.
custody of repair parts, storerooms with bins and
drawers for individual stowage of repair part items are
generally used instead of the repair parts boxes. The
available space and the type of work done in the shop
are factors that determine how much material is stowed
in the shops and how much is stowed in storerooms.
STOWAGE.—Whenever possible, repair parts
should be stowed in special storerooms. On small ships,
where it may be impracticable to stow repair parts
boxes in storerooms, the boxes are generally located in
(or near) the same space as the machinery for which
they are required. Where the supply department has
Pipe Shop Stowage.—In a tender or repair ship
pipe shop, for example, you will probably not have
the stowage of material and equipment. Some of thest
important of these are as follows:
room for all the varied sizes and lengths of materials
that you may use. However, storage should be provided
in the pipe shop for the most commonly used pipe sizes
and also for the leftover lengths that accumulate in the
course of time. Overhead or bulkhead storage racks are
often used for stowage of piping. Stowage should be
provided in the pipe shop for the most commonly used
valves, fittings, bolts, nuts, rivets, and other items
required for piping repairs.
Stow material neatly and in such a way that
you can get it when you need it.
Identify all materials. A piece of carbon
molybdenum steel looks just like a piece of
mild steel, but you cannot use the two materials
for the same purpose. Materials should be
identified by labels for each bin or rack, by
shipping tags attached to the materials, by
color-code markings (when applicable), and by
stock number. Keeping the stock number with
the material will save you time and trouble
when you need to reorder material.
Weld Shop Stowage.—In a welding shop, you will
have the problem of stowing welding machines,
welding rods, protective equipment, and all the other
gear required for welding. Particular precautions should
be taken in stowing electrodes to make sure that they
will be kept dry and that the coated surfaces will not be
Protect all materials against rust and other
corrosion and against other kinds of damage.
Sheet Metal Shop Stowage.—In the sheet metal
shop and in the shipfitter shop, the stowage of large
sheets, bars, or structural shapes will present special
problems. In a general-purpose HT shop, the requirements vary so much from day to day that you will
probably find it impracticable to stow large amounts of
any one material; instead, you will draw your material
as you need it from a storeroom. The main stowage
problem that you are likely to have in a general-purpose
HT shop is the stowage of leftover materials.
Be sure that your stowage facilities include
provision for securing for sea. Metal sheets,
bars, structural shapes, pipes, and tubes must be
secured so that they will not shift when the ship
is underway. Padeyes, turnbuckles, wedges,
bars, and C-clamps can be used to secure
Within the limits of available space, provide
stowage facilities that will make the shop a
convenient place to work.
type of shop you are in, certain general rules apply to
Figure 2-6.—Shell section of a destroyer.
additional member is attached to this flange to serve as
the center strake.)
In the repair of ships, it is important that you have
an understanding of basic ship structure. Therefore, the
following section will discuss the structural parts of a
ship and the purpose of the parts.
The web of the I-beam is a solid plate that is called
the vertical keel. The upper flange is called the rider
plate; this forms the center strake of the inner bottom
plating. An inner vertical keel of two or more sections,
consisting of I-beams arranged one on top of the other,
is found on many large combatant ships.
The principal strength members of the ship’s
structure are located at the top and bottom of the hull
where the greatest stresses occur. The top section
includes the main deck plating, the deck girders, and
the sheer strakes of the side plating. The bottom section
includes the keel, the outer bottom plating, the inner
bottom plating, and any continuous longitudinals in way
of the bottom. The side webs of the ship girder are
composed of the side plating, aided to some extent by
any long, continuous fore-and-aft bulkheads. Some of
the strength members of a destroyer hull girder are
indicated in figure 2-6.
Frames used in ship construction may be of various
shapes. Frames are strength members. They act as
integral parts of the ship girder when the ship is
exposed to longitudinal or transverse stresses. Frames
stiffen the plating and keep it from bulging or buckling.
They act as girders between bulkheads, decks, and
double bottoms, and transmit forces exerted by load
weights and water pressures. The frames also support
the inner and outer shell locally and protect against
unusual forces, such as those caused by underwater
explosions. Frames are called upon to perform a variety
of functions, depending upon the location of the frames
in the ship. Figure 2-8 shows various types of frames
used on board ship.
The keel is the most important structural member of
a ship. It is considered to be the backbone of the ship.
The keel is built up of plates and angles into an I-beam
shape (fig. 2-7). The lower flange of this I-beam
structure is the flat keel plate, which forms the center
strake of the bottom plating. (On large ships, an
There are two important systems of framing in
current use:the transverse framing system and the
longitudinal framing system. The transverse system
provides for continuous transverse frames with the
widely spaced longitudinals intercostal between them.
Transverse frames are closely spaced and a small
number of longitudinals are used. The longitudinal
system of framing consists of closely spaced
longitudinals, which are continuous along the length of
the ship, with transverse frames intercostal between the
Transverse frames are attached to the keel and
extend from the keel outward around the turn of the
bilge and up to the edge of the main deck. They are
closely spaced along the length of the ship, and they
define the form of the ship.
Figure 2-7.—Typical welded keel section.
Figure 2-8.—Types of frames used on board ship.
Longitudinals (fig. 2-9) run parallel to the keel
along the bottom, bilge, and side plating. The
longitudinals provide longitudinal strength, stiffen the
shell plating, and tie the transverse frames and the
bulkheads together. The longitudinals in the bottom
(called side keelsons) are of the built-up type (fig.
Where two sets of frames intersect, one set must be
cut to allow the other to pass through. The frames,
Figure 2-11.—Intercostal and continuous frames.
which are cut and thereby weakened, are known as
intercostal frames; those that continue through are
called continuous frames. Both intercostal and
continuous frames are shown in figure 2-11.
A cellular form of framing results from a
combination of longitudinal and transverse framing
systems using closely spaced deep framing. Cellular
framing is used on most naval ships.
In the bottom framing, which is normally the
strongest portion of the ship's structure, the floors and
keelsons are integrated into a rigid cellular construction
(fig. 2-12). Heavy loads, such as the ship’s propulsion
machinery, are bolted to foundations that are built
directly on top of the bottom framing (fig. 2-13). (This
method is outdated and is being replaced by block
assembly technology.)
In many ships, the top of this cellular region is
covered with shell plating, which forms many tanks or
voids in the bottom of the ship. The plating over the
intersection of the frames and longitudinals is known as
the inner bottom plating. The inner bottom plating is a
watertight covering laid on top of the bottom framing.
It is a second skin inside the bottom of the ship. It
prevents flooding in the event of damage to the outer
bottom, and it also acts as a strength member. The
tanks and voids may be used for stowage of fresh water
or fuel oil or they can be used for ballasting. This type
of bottom structure, with inner bottom plating, is called
double-bottom construction.
Figure 2-9.—Basic frame section (longitudinal framing).
The ship's bow, which is the front of the ship,
varies in form from one type of ship to another as the
requirements of resistance and seakeeping dictate the
Figure 2-10.—Built-up longitudinal.
Figure 2-12.—Bottom structure.
rigidly fasten together the peak frames, the stem, and
the outside plating. Breast hooks are made of heavy
plate and are basically triangular in shape.
Deep transverse framing and transverse bulkheads
complete the stem assembly. The stem itself is
fabricated from castings, forgings, and heavy plate, or
in the case of smaller ships, heavy, precut structural
steel plate.
The after-most section of the ship's structure is the
stem post, which is rigidly secured to the keel, shell
plating, and decks. On single-screw ships, the stem post
is constructed to accommodate the propeller shaft and
rudder stock bosses. The stem post as such is difficult
to define, since it has been replaced by an equivalent
structure of deep framing. This structure (fig. 2-15)
consists of both longitudinal and transverse framing that
extends throughout the width of the bottom in the
vicinity of the stem. To withstand the static and
dynamic loads imposed by the rudders, the stem
structure is strengthened in the vicinity of the rudder
post by a structure known as the rudder bearing
Figure 2-13.—Deep floor assembly for machinery foundations.
shape. The external shape is shown in figure 2-14 and
is commonly used on combatant ships. This form is
essentially bulbous at the forefoot, tapering to a sharp
entrance near the waterline and again widening above
the waterline. Internally, the stem assembly has a heavy
centerline member that is called the stem post. The stem
post is recessed along its after edge to receive the shell
plating, so that the outside presents a smooth surface to
cut through the water. The keel structure is securely
fastened to the lower end of the stem by welding. The
stem maintains the continuity of the keel strength up to
the main deck. The decks support the stem at various
intermediate points along the stem structure between the
keel and the decks.
The outer bottom and side plating forms a strong,
watertight shell. Shell plating consists of approximately
rectangular steel plates arranged longitudinally in rows
or courses called strakes. The strakes are lettered,
beginning with the A strake, which is just outboard of
the keel, and working up to the uppermost side strake.
At various levels and at regular intervals along the
stem structure between the keel and the decks are
horizontal members called breast hooks. Breast hooks
Figure 2-14.—Bulbous-bow configuration.
very much upon the strength and tightness of the
connections between the individual pieces. In today’s
modern naval vessels, joints are welded flush together
to form a smooth surface.
The end joint formed by adjoining plates in a strake
is called a butt. The joint between the edges of two
adjoining strakes is called a seam. Seams are also
welded flush. Butts and seams are illustrated in figure
In general, seams and butts are located so that they
do not interfere with longitudinals, bulkheads, decks,
and other structural members. Since the hull structure is
composed of a great many individual pieces, the
strength and tightness of the ship as a whole depend
Bilge keels are fitted in practically all ships at the
turn of the bilge. Bilge keels extend 50 to 75 percent of
the length of the hull. Bilge keels consist of two plates
forming a “V” shape welded to the hull, and on large
Figure 2-15.—Stern Structure.
Figure 2-16.—Section of a ship, showing plating and framing.
stringer strake is usually heavier than the other deck
strakes, and it serves as a continuous longitudinal
stringer, providing longitudinal strength to the ship’s
ships may extend out from the hull nearly 3 feet. Bilge
keels serve to reduce the extent of the ship's rolling.
Decks provide both longitudinal and transverse
strength to the ship. Deck plates, which are similar to
the plates used in side and bottom shell plating, are
supported by deck beams and deck longitudinales.
To reinforce the deck transverses and to keep the
deck transverse brackets and side frames from carrying
the total load, vertical stanchions or columns are fitted
between decks. Stanchions are constructed in various
ways of various materials. Some are made of pipe or
rolled shapes. The stanchion shown in figure 2-18 is in
fairly common use; this pipe stanchion consists of a
steel tube that is fitted with special pieces for securing
it at the upper end (head) and at the lower end (heel).
The term uppermost strength deck is applied to the
deck that completes the enclosure of the box girder and
the continuity of the ship's structure. It is the highest
continuous deck—usually the main or weather deck.
The term strength deck also applies to any continuous
deck that carries some of the longitudinal load. On
destroyers, frigates, and similar ships in which the main
deck is the only continuous high deck, the main deck is
the strength deck. The flight deck is the uppermost
strength deck on aircraft carriers (CVs and LHDs) that
carry helicopters, but the main or hangar deck is the
strength deck on older types of carriers.
Bulkheads are the vertical partitions that, extending
athwartships and fore and aft, provide compartmentation
to the interior of the ship. Bulkheads may be either
structural or nonstructural. Structural bulkheads, which
tie the shell plating, framing, and decks together, are
capable of withstanding fluid pressure; these bulkheads
usually provide watertight compartmentation. Nonstructural bulkheads are lighter; they are used chiefly for
separating activities aboard ship.
The main deck is supported by deck transverses and
deck longitudinales. Deck transverses are the transverse
members of the framing structure. The transverse beams
are attached to and supported by the frames at the sides,
as shown in figure 2-17. Deck girders are similar to
longitudinales in the bottom structure in that they run
fore and aft and intersect the transverse beams at right
Bulkheads consist of plating and reinforcing beams.
The reinforcing beams are known as bulkhead stiffeners
(fig. 2-19). Bulkhead stiffeners are usually placed in the
The outboard strake of deck plating that connects
with the shell plating is called the stringer strake. The
Figure 2-18.—Pipe stanchion.
Figure 2-17.—Transverse beam and frame.
of flooding in the compartments that they bound. To
form watertight boundaries, structural bulkheads must
be joined to all decks, shell plating, bulkheads, and
other structural members with which they come in
contact. Main subdivision bulkheads extend through the
watertight volume of the ship, from the keel to the
bulkhead deck, and serve as flooding boundaries in the
event of damage below the waterline.
Ship repair is the fundamental duty of the Hull
Maintenance Technician. In this chapter, you have been
exposed to the basic organization of the IMA and some
of the personnel assigned to this type of organization.
You have also been exposed to the basics of the QA
program and its link to maintenance. When assigned to
your command you should study your command’s
organization and QA program for a greater understanding of your role in that organization. As you gain
experience and advance in rate you will be given the
opportunity to become a work center supervisor. The
appointment as a work center supervisor carries a lot of
responsibility and accountability for your actions. But
the role of a work center supervisor is often a rewarding and challenging position. As a work center
supervisor you will be expected to organize, plan, and
supervise the completion of various tasks that met all
the requirements of the QA program.
Figure 2-19.—Bulkhead stiffeners.
vertical plane and aligned with deck longitudinales; the
stiffeners are secured at top and bottom to any
intermediate deck by brackets attached to deck plating.
The size of the stiffeners depends upon their spacing,
the height of the bulkhead, and the hydrostatic pressure
that the bulkhead is designed to withstand.
Bulkheads and bulkhead stiffeners must be strong
enough to resist excessive bending or buckling in case
Upon completion of this chapter, you should be able to do the following:
Identify, the various characteristics of wood, and tree growth and structure.
Identify the various methods used in cutting and seasoning lumber.
Identify common defects and blemishes of lumber.
Identify the various grades of lumber and the methods used to measure
Identify types of wood joinery to include cuts, joints, fasteners, and materials.
Recognize the proper method and necessary took and equipment for laying
out and cutting joints.
Identify applications for the various joints.
Recognize the purpose and use of different types of fastening materials.
Identify the types of glue and their application methods.
Identify the various sanding materials and their proper uses.
Although Navy ships are now made largely of
steel and other metals, there is still plenty of
woodworking for HTs to do. Cruisers and carriers
usually have a shop equipped with the necessary
handtools and three or more standard woodworking
machines; tenders and repair ships have large shops
with all types of woodworking machines.
In the lumber industry, woods are classified as
hardwoods or softwoods. These two terms are more
as a matter of convenience than as an exact
classification. In fact, this classification does not
depend on how hard the wood is. It depends on
what kind of leaves the trees have. If the tree has
broad leaves that shed in winter, the wood is
classified as hardwood. If the tree has needle leaves
and cones, the wood is classified as softwood.
These classifications are somewhat confusing
because some softwoods are harder than some
hardwoods, and some hardwoods are softer than
most softwoods.
An HT is required to have a knowledge of the
types of wood and woodworking glue, the principles
of wood finishing, and to be able to solve problems
dealing with the number of board feet in a piece of
lumber. This chapter provides information related
to these requirements.
Hardwoods are used in construction and repair
work because of their strength, durability, and ability
to resist warpage. They are used to make furniture,
dowels, and some patterns. Hardwoods include ash,
birch, beech, white oak, poplar, walnut, and maple.
HTs prefer softwoods for most patterns because
they work easily. Softwoods are also used as
structural lumber, boat planking, and for shoring.
Softwoods include white cedar, cypress, Douglas fir,
white pine, yellow pine, and redwood.
Wood consists of small cells. The size and
arrangement of these cells determine the grain of
the wood and many of its properties. Look at a
freshly cut tree stump. You will see thousands of
large and small cells arranged in circular rings
around the pith or center of the tree. The large
cells have thin walls, and the smaller cells have thick
walls (figs. 3-1 and 3-2). Rings form because of a
difference in the growth rate during various seasons
of the year. In spring, a tree grows rapidly and
builds up a layer of soft, large cells. These cells
appear in the cross section of the trunk as the
light-colored rings (spring rings).
Figure 3-2.—Structure of wood.
and the bark (fig. 3-1). Sapwood is lighter in color
than heartwood.
The cambium layer (fig. 3-1) is the boundary
between the sapwood and the bark. New sapwood
cells form in this thin layer.
Medullary rays (fig. 3-1) are radial lines of wood
cells. They are highly visible. Their function is to
move cell liquids horizontally in the tree trunk.
When speaking of medullary rays, we use thickness
to refer to the horizontal dimension, and width to
refer to the vertical dimension.
As the weather gets hotter during early summer,
the growth rate slows. The summer cells form
closer together and become dark rings (summer
rings). The age of a tree can be determined very
accurately by counting these dark rings. Some trees,
such as oak and walnut, have very distinctive rings.
White pine is so uniform that you can barely see the
When a tree is sawed lengthwise, the annual
rings form a pattern called the grain. Several terms
describe wood grain.
If the wood cells that form the grain are
closely packed and small, the wood is
fine-grained or close-grained. Maple and
birch are good examples.
The sapwood of a tree is the outer section of the
tree between the heartwood (darker center wood)
If the cells are large and porous, the wood
is coarse-grained or open-grained. Oak,
walnut, and mahogany are examples of
coarse-grained wood.
When the wood cells are straight and
parallel to the trunk of the tree, the wood is
If the grain is crooked, slanting, or twisted,
the wood is cross-grained.
Figure 3-1.—Cross section of a tree.
When a log is sawed lengthwise into boards,
each saw cut crosses the annual rings at an angle.
If the angle between the saw cut and the rings is 45°
or greater, the board has a vertical grain. If the
angle is less than 45°, the board has a flat grain. If
the log feeds through without turning, the first few
outside boards cut off will be flat-grained. The
boards cut from the center section will be
vertical-grained. The last few boards cut will be
flat-grained. By turning the log between saw cuts
(fig. 3-3), you can produce all vertical-grained or all
flat-grained lumber.
Slash cutting is the easier, quicker, and less
wasteful of the two methods. The surface knots that
appear in slash-cut lumber affect the strength of the
lumber much less than the knots that appear in
rift-cut lumber. However, if a log is sawed to
produce all slash-cut lumber, more boards will have
knots than if the log were all rift cut.
Rift-cut lumber provides edge grain on both
faces. If hardwood is rift cut, it is quarter-sawed
lumber. If softwood is rift cut, it is edge-grain
lumber. When an entire log is slash cut, several
boards near the center of the log will actually be rift
Vertical-grained wood resists wear better than
flat-grained wood of the same species. Most
flat-grained wood will take and hold a finish better
than most vertical-grained wood. Use the term
texture to express the relative size of the pores
(cells) and fibers as coarse or fine textured and even
or uneven textured.
Getting as many edge-grained boards as possible
from a tree requires that the logs first be sawed into
quarters (fig. 3-3). Then, each quarter is sawed into
planks by one of the four methods shown. The
method used depends on the intended use for the
lumber. Radial quarter sawing will yield lumber
that is stronger and will warp less than that gotten
by any other method of sawing. The disadvantages,
however, are that this method is more costly, takes
longer, and is more wasteful of material.
In a large lumber mill, logs are processed into
lumber with huge band saws and circular saws. The
two methods of sawing the logs are slash cutting and
rift cutting (fig. 3-4). Slash cutting is from a series
of parallel cuts. If hardwoods are cut, the process
is termed plain sawing. If softwoods are cut, the
process is termed flat-grain sawing.
Once lumber has been sawed, it must be
seasoned (dried). The purpose of seasoning is to
remove the moisture from the cells. Moisture
(water or sap) occurs in two separate forms—free
water and imbibed water. Free water is the
moisture the individual cells contain internally.
Imbibed water is the moisture contained by the cell
walls. During drying or seasoning, the free water
evaporates until a minimum remains. The amount
of moisture remaining is the fiber-saturation point.
Figure 3-4.—Slash cutting and rift cutting.
Figure 3-3.—Four methods of quarter sawing.
worms, and fungi, which can cause defects either
before or after the lumber is cut. Improper
seasoning causes other defects and blemishes.
The fiber-saturation point varies from 25 to 30
percent, but for general purposes is accepted as 30
percent. Below the fiber-saturation point, the
imbibed water extracts from the cell walls, causing
a reduction in the thickness of the walls.
The most common defects are knots. Knots
occur in most kinds of lumber and are the result of
branch growth. An interwoven knot forms while the
tree is alive. Its annual rings are interwoven with
those of the trunk of the tree. Usually an
interwoven knot is solid and is not a serious defect.
If the limb dies before the tree is cut, the wood
formed in the trunk of the tree makes no further
connection with the limb, but grows around it. This
produces a dead knot. This may be loose enough to
drop out or may be tight enough to hold its shape
and position when the tree is being sawed into
lumber. A spike knot is a long, thin knot caused by
the way the tree was sawed. Small, solid knots are
not objectionable in most of the lumber used aboard
ship. If lumber has loose or large knots, you should
cut it into smaller pieces to eliminate these defects.
Wood shrinks across the grain when the
moisture content lowers below the fiber-saturation
point. Evaporation or absorption of moisture causes
shrinking and swelling of the wood cells, changing
the size of the cells. Therefore, the lowering or
raising of the moisture content causes lumber to
shrink or swell.
The loss of moisture during seasoning causes
wood to be (1) harder, (2) stronger, (3) stiffer, and
(4) lighter in weight. There are two methods for
seasoning lumber—air drying and kiln drying.
Air-dried lumber is exactly what the name
implies. It is wood placed in a shed or in the open
to dry. This method takes up to 7 years to season
some woods.
Heartshake and windshake (fig. 3-5) are other
lumber defects. Heartshake is caused by the action
of the wind and is a lengthwise separation of the
annual rings. Windshake is also a defect caused by
the action of the wind, which causes the tree to
A faster method of drying is known as kiln
drying. The wood is placed in a kiln and treated
with steam. The time required for drying varies
from 2 or 3 days to several weeks. Often a
combination of air-dried and kiln-dried methods is
used to dry lumber.
A CHECK is a crack or separation, usually
short, caused by the uneven shrinking of the wood
cells in seasoning. Do not confuse these with pitch
pockets. Pitch pockets are small enclosed spaces in
the wood filled with sap or pitch (rosin).
Lumber is dry enough for most uses when the
moisture content reduces to about 12 or 15 percent.
However, lumber used for patterns should be drier.
The moisture content should be 8 or 10 percent for
hardwoods and 10 to 12 percent for softwoods. As
an HT, you will learn to judge the dryness of a
wood by its color, weight, smell, and feel. Looking
at the shavings and chips also helps identify wood.
WARP or WARPAGE is a lumber defect in
which a board distorts from a true, flat surface; it is
twisted, bowed, or cupped warped. The varying
amount of moisture in the wood changes the
diameter of the cells. This causes the board to
shrink or swell in width as well as in thickness, but
not in length. Redwood is an exception because it
will swell or shrink in all three dimensions.
A defect in lumber is any flaw that affects the
strength, durability, or utility value of the lumber.
A blemish is a flaw that mars only the appearance
of the lumber. A blemish that affects the utility
value of the lumber (such as a blemish in wood
intended for fine furniture or cabinet work) is also
a defect.
You will seldom find a piece of lumber that
does not have a defect or blemish of some sort.
Some defects and blemishes are the result of decay
in the growing tree. Others are the result of insects,
Figure 3-5.—Defects in logs.
WANE is a term that identifies a board that is
not full or true to size. It lacks wood along corners,
edges, or ends, or is partially composed of bark.
All softwood framing lumber, and most other
softwood lumber, is cut to even-numbered foot
lengths, such as 10 feet, 12 feet, and 14 feet.
Hardwood is sometimes cut to odd-numbered as
well as even-numbered foot lengths.
BLUE STAIN is a blemish caused by a mold
fungus. It does not weaken the wood.
Hardwoods used for cabinets, furniture, and
other finish work are cut to specific thicknesses (in
graduations of 1/4 inch). They are cut to random
widths and lengths (RWL) with a specified
minimum. For example, a written order for walnut
would be 4/4x4x6 RWL. This would tell the
supplier that you require material 1 inch thick (4/4),
at least 4 inches wide, and at least 6 feet long.
A BARK POCKET is a patch of bark that has
had the tree grow over. It is entirely or almost
entirely enclosed.
CROSS-GRAINED LUMBER has grain that is
not parallel to the length of the lumber.
There are several lumber defects caused by
improper seasoning. One common one is
honeycombing. Honeycombing is a series of checks
or cracks on the surface or in the center of the
lumber caused by drying stresses. If the stress is not
relieved by the addition of moisture during the
seasoning process, honeycombing will result.
Lumber grades are based on the type and extent
of defects, size of the pieces, and seasoning
condition. Softwood lumber is graded for quality
according to American Lumber Standards. These
standards are set by the National Bureau of
Standards for the U.S. Department of Commerce.
The major quality grades, in descending order of
quality, are select lumber (usually used for interior
finish) and common lumber (usually used for house
Each grade has subdivisions in
descending order of quality as follows:
Lumber is sized according to how thick it is.
Boards are pieces of lumber less than 2 inches thick.
Planks or dimension lumber are pieces of lumber
from 2 to 5 inches thick. Timbers are heavier
pieces. Softwoods are usually cut to standard
thicknesses, widths, and lengths.
1. Select lumber
The dressed dimensions of lumber are always
smaller than the specified size (nominal size) (table
3-1). The nominal size is the size of the lumber in
its rough form as it comes from the saw mill.
Dressed lumber has been surfaced (planed smooth)
on two or four sides. Lumber surfaced on two sides
is S2S (surfaced on two sides). Lumber surfaced on
four sides is S4S (surfaced on four sides).
Grade A lumber. This lumber is select
lumber that is practically free of defects and
Grade B lumber. This is select lumber that
contains a few minor blemishes.
Grade C lumber. This is finish item lumber
that contains more blemishes and more significant
blemishes than grade B. These blemishes must be
able to be easily and thoroughly concealed with
Table 3-1.—Nominal and Dressed Lumber Sizes
Nominal Size
Dressed Dimensions
1 5/8 × 1 5/8
1 5/8 × 3 5/8
1 5/8 × 5 5/8
1 5/8 × 7 1/2
2 × 10
1 5/8 × 8 1/2
2 × 12
1 5/8 × 11 1/2
3 5/8 × 3 5/8
Grade D lumber. This is finish item lumber
that contains more blemishes and more significant
blemishes than grade C, but it is still capable of
presenting a satisfactory appearance when painted.
2. Common lumber
No. 1 common lumber. This is sound,
tight-knotted stock containing only a few minor
It is common practice to state the thickness
dimension in inches first; the width in inches second;
and the length in feet last. For example, if you were
told to get a 2 by 4 by 6, you would know to get a
board 2 inches thick by 4 inches wide by 6 feet long.
defects. It must be suitable for use as watertight
No. 2 common lumber. This lumber
contains a few significant defects, but no knotholes
or other serious defects.
The standard measure for lumber is a board
foot. This is abbreviated as bf or bd ft. A board
foot is simply one-twelfth of a cubic foot. A board
measuring 1 inch thick, 12 inches wide, and 12
inches long contains 1 bd ft. Figure 3-6 shows
different size pieces of wood. Each one contains 1
bd ft.
No. 3 common lumber. This lumber
contains a few defects that are larger and coarser
than those in No. 2 common; for example,
occasional knotholes.
No. 4 common lumber. This lumber is low
quality and contains serious defects like knotholes,
checks, shakes, and decay.
You may use several formulas to determine bd
ft. The one most commonly used is the inches,
inches, feet method. To use it, multiply the
thickness (T) in inches by the width (W) in inches
by the length (L) in feet. Next, divide the product
by 12. Write the formula as follows:
No. 5 common lumber. This lumber is
capable only of holding together under ordinary
Mill-run lumber is everything that is sawed
except the slabs (bark). Some associations use
grades of construction known as standard, utility,
and economy.
bd ft = T(in.) × W(in.) × L(ft.)
Suppose you want to determine the bd ft
contained in a piece of wood measuring 1 inch thick
by 8 inches wide by 9 feet long. Using the formula,
you would work it like this:
All species of lumber are covered by the grading
rules and size standards of some association or
grading bureau. Softwood lumber standards are set
by a regional association of manufacturers. In a few
cases, a softwood species growing in more than one
region is graded under rules of two different
associations. It is better to buy according to these
association grades than to try to buy according to
individualspecifications, unless the requirements are
very unusual. Occasionally a departure from the
standard grade provision is necessary. This is
handled as an exception to a standard grade.
bd ft = T(in.) × W(in.) × L(ft.)
bd ft =
1(in.) × 8(in.) × 9(ft.)
bd ft = 6
Hardwoods are graded as firsts, seconds, selects,
No. 1 common, and No. 2 common. These grades
indicate only the amount of clear usable lumber in
a particular piece. They are established by the
National Hardwood Manufacturers’ Association.
The way to buy hardwoods for any use other than
construction is by personal inspection.
Therefore, a board measuring 1 inch by 8 inches by
9 feet will contain 6 bd ft.
When you are measuring lumber, thickness is the
dimension between the two face surfaces, Width is
the dimension between the two edges that are
parallel to the wood grain. Length is the dimension
between two ends and is parallel to the wood grain
regardless of the width dimension.
Figure 3-6.—The board foot.
measurement of a piece of lumber. Therefore, if
you had a 2 by 4 by 6, its linear measurement would
be 6 feet. This method is often used when buying
dimensioned lumber for construction purposes.
A board less than 1 inch thick is figured as 1
inch when you are calculating bd ft. A board more
than 1 inch thick is figured to the next larger
1/4-inch increment. Thus, a board having a
thickness of 1 1/8 inches calculates as 1 1/4 inches.
Board measure calculates on the basis of the
nominal not the dressed dimension of the lumber.
Before proceeding with this chapter, review the
sources, uses, and characteristics of the various types
of common woods provided in table 3-2.
Another common way of measuring lumber is by
linear measure. Linear measure is simply the length
Table 3-2.—Common Woods
East of Rockies.
Oars, boat thwarts,
benches, gratings,
hammer handles,
cabinets, ball bats, wagon
construction, farm
Strong, heavy, hard, tough,
elastic, close straight grain,
shrinks very little, takes excellent
finish, lasts well.
Rafts, food boxes, linings
of refrigerators, life
reserves, loud speakers,
sound-proofing, air-conditioning devices, model
airplane construction.
Lightest of all woods. Very soft,
strong for its weight, good heat
insulating qualities, odorless.
Eastern half of U.S.
with exception of
coastal regions.
Low-grade furniture,
cheaply constructed
buildings, interior finish,
shelving, drawers, boxes,
drainboards, woodenware, novelties, excelsior,
general millwork.
Soft, very light, weak, brittle, not
durable, shrinks considerably.
Interior to poplar, but very
uniform, works easily. Takes
screws and nails well and does
not twist or warp.
East of Mississippi
River, Southeastern
Cabinetwork, imitation
mahogany furniture,
wood dowels, capping,
boat trim, interior finish,
tool handles, turnery,
shoe lasts, carving,
Similar to birch but not so
durable when exposed to
weather. Shrinks and checks
considerably. Close-grained,
light or dark red color.
East of Mississippi
River and north of Gulf
Coast States, Southeast
Canada, Newfoundland.
Cabinetwork, imitation
mahogany furniture,
wood dowels, capping,
boat trim, interior finish,
tool handles, turnery,
Hard, durable, fine grain, even
texture, heavy, stiff, strong,
tough. Takes high polish, works
easily. Forms excellent base for
white enamel finish, but not
durable when exposed.
Heartwood is light to dark
reddish brown in color.
Table 3-2.—Common Woods—Continued
Southern Canada,
Minnesota, Eastern
U.S. as far south as
Alabama and Florida.
Toys, altars, woodenware,
millwork, interior trim,
furniture, boats, scientific
Very much like walnut in color
but softer. Not so soft as white
pine and basswood. Easy to
work, coarse-grained, fairly
Maryland to Texas,
along Mississippi
Valley to Illinois.
Small boat planking,
siding, shingles, sash,
doors, tanks, silos, railway
Many characteristics similar to
white cedar. Water-resistant
qualities make it excellent for use
as boat planking.
Doulgas fir
Pacific Coast, British
Patternmaking, deck
planking on large ships,
shores, strongbacks, plugs,
filling pieces and
bulkheads of small boats,
building construction,
dimension timber,
Excellent structural lumber.
Strong, easy to work, clear
straight grained, soft but brittle.
Heartwood is durable in contact
with ground. Best structural
timber of northwest.
States east of
Agricultural implements,
wheel-stock, boats,
furniture, crossties, posts,
Slippery, heavy, hard, tough.
Durable, difficult to split, not
resistant to decay.
Arkansas, Tennessee,
Ohio, Kentucky.
Tools, handles, wagon
stock, hoops, baskets,
vehicles, wagon spokes.
Very heavy, hard, stronger and
tougher than other native wood,
but checks and shrinks. Difficult
to work. Subject to decay and
insect attack.
Central America.
Patternmaking, block
sheaves, and pulleys,
water-exposed shaft
bearings of small boats
and ships, tool handles,
small turned articles, and
mallet heads.
Dark greenish brown. Unusually
hard, close-grained, very heavy,
resinous. Difficult to split and
work, has soapy feeling.
Live oak
Southern Atlantic and
Gulf Coasts of U.S.,
Oregon, California.
Implements, wagons,
Very heavy, hard, tough, strong,
durable. Difficult to work. Light
brown or yellow sap wood nearly
Honduras, Mexico,
Central America,
Florida, West Indies,
Central Africa, other
tropical sections.
Patternmaking, furniture,
boats, decks, fixtures,
interior trim in expensive
homes, musical
Brown to red color. One of
most useful of cabinet woods,
hard, durable. Does not split
badly. Open-grained, takes
beautiful finish when grain is
filled but checks, swells, shrinks,
warps slightly.
Table 3-2.—Common Woods—Continued
All states east of
Colorado, Southern
Patternmaking, excellent
furniture, high-grade
floors, tool handles, ship
construction crossties,
counter tops, bowling pins.
Fine-grained, grain often curly or
“bird's eyes.” Heavy, tough, hard,
strong. Rather easy to work, but
not durable. Heartwood is light
brown, sap wood is nearly white.
States bordering Great
Dimension timber, masts,
spars, piling, interior trim.
Light, fairly hard, strong. Not
durable in contact with ground.
Philippine Islands
Patternmaking, pleasure
boats, medium-grade
furntiure, interior trim.
Not a true mahogany. Shrinks,
expands, splits, warps, but
available in long, wide, clear
Virginias, Tennessee,
Kentucky, Mississippi
Patternmaking, low-grade
furniture, cheaply
constructed buildings,
interior finish, shelving,
drawers, boxes.
Soft, cheap obtainable in wide
boards. Warps, shrinks, rots
easily. Light, brittle, weak, but
works easily and hold nails well,
Red cedar
East of Colorado and
north of Florida.
Mothproof chests, lining
for linen closets, sills, and
other uses similar to white
Very light, soft, weak, brittle, low
shrinkage. Great durability,
fragrant scent. Generally knotty,
beautiful when finished in
natural color. Easily worked.
Red oak
Virginias, Tennessee,
Arkansas, Kentucky,
Ohio, Missouri,
Interior finish, furniture,
cabinets, millwork,
crossties when preserved.
Tends to warp. Coarse-grained.
Does not last well when exposed
to weather. Porous easily
impregnated with preservative.
Heavy, tough, strong.
Patternmaking, general
construction, tanks,
Inferior to yellow pine and fir in
strength. Shrinks and splits little.
Extremely soft, light straightgrained. Very durable,
exceptionally decay resistant.
New York, New
England, West
Virginia, Central
Canada, Great Lakes
states, Idaho,
Washington, Oregon.
Railway ties, resonance
wood, piles, airplanes,
oars, masts, spars, baskets.
Light, soft, low strength, fair
durability, close grained,
yellowish, sap wood indistinct.
Sugar pine
California, Oregon.
Same as white pine.
Very light, soft, resembles white
India, Burma, Java,
Deck planking, shaft logs
for small boats.
Light brown color. Strong, easily
worked, durable, resistant to
damage by moisture.
Table 3-2.—Common Woods—Continued
Eastern half of U.S.
except Southern
Atlantic and Gulf
Coasts, some in New
Mexico, Arizona,
Expensive furniture,
cabinets, interior
woodwork, gun stocks,
tool handles, airplane
propellers, fine boats,
musical instruments.
Fine cabinet wood. Coarsegrained but takes beautiful finish
when pore closed with wood
filler. Medium weight, hard,
strong. Easily worked. Dark
chocolate color. Does not warp
or check, brittle.
White cedar
Eastern Coast of U.S.
and around Great
Boat planking, railroad
ties, shingles, siding posts,
Soft, light weight, close-grained.
Exceptionally durable when
exposed to water. Not strong
enough for building construction.
Brittle, low shrinkage, generally
White oak
Virginias, Tennessee,
Arkansas, Kentucky,
Ohio, Missouri,
Maryland, Indiana.
Boat and ship stems,
sternposts, knees, sheer
strakes, fenders, capping,
transoms, shaft logs,
framing for buildings,
strong furniture, tool
handles, crossties,
agricultural implements,
fence posts.
Heavy, hard, strong. Medium
coarse-grained. Tough, dense,
most durable of hardwoods.
Elastic, rather easy to work, but
shrinks and likely to check.
Light brownish grey in color with
reddish tines. Medullary rays are
large and outstanding and
present beautiful figures when
quarter sawed. Receives high
White pine
Minnesota, Wisconsin,
Maine, Michigan,
Idaho, Montana,
Washington, Oregon,
Patterns, any interior job
or exterior job that
doesn’t require strength,
window sash, interior trim,
millwork, cabinets,
Easy to work. Fine-grained, free
of knots. Takes excellent finish.
Durable when exposed to water,
expands when wet, shrinks when
dry. Soft, white. Nails without
splitting, not very strong,
Yellow pine
Virginia to Texas.
Most important lumber
for heavy construction and
exterior work, keelsons,
risings, filling pieces,
clamps, floors, bulkheads
of small boats, shores,
wedges, plugs,
strongbacks, staging, joists,
posts, piling, ties, paving
Hard, strong, heartwood is
durable in the ground. Grain
varies. Heavy, tough, reddish
brown in color. resinous,
medullary rays well marked.
much moisture or pitch. Such boards are difficult
to work with, shrink excessively, and will not keep a
smooth surface.
Woods that have a comparatively straight, close
grain, that are easy to work, and that do not warp or
shrink easily are the woods you should select for
pattern work. Do not select boards containing too
A board that contains excess pitch may be
unusually heavy. When planed, large amounts of
pitch may be seen. Excessive moisture cannot
always be detected by weight. Detection comes
when the board is crosscut or dressed.
direction of the grain, but it is excellent for
cross-grain carving. Mahogany will outlast pine 3
to 1.
Kinds of Lumber
Several varieties of mahogany are used. Spanish
mahogany is from the West Indies, Honduras
mahogany (also called baywood) and Mexican
mahogany is from Central America and Mexico, and
Senegal mahogany is from Africa. Distinguishing
between varieties is difficult. Mahogany is usually
reddish-brown, but it often varies in color.
The woods most frequently used in the
carpenter shop for most projects are redwood, white
pine, ponderosa pine, mahogany, and poplar.
REDWOOD is inferior to the better grades of
sugar pine and white pine, but for most patterns it
works well. The best grades work easily. Redwood
has one peculiar property that no other wood has—it
shrinks in length as well as in thickness and in
width. The name redwood derives from the
reddish-brown color of the wood itself. It is related
to pine but is much more durable when in contact
with soil or when exposed to weather.
POPLAR is used in many carpenter and pattern
shops. It is soft with close, straight grain. Its use is
limited because of brittleness and excessive warping
and shrinkage. Poplar ranges in color from
off-white to light yellow. The poplar tree grows in
the eastern part of the United States. It goes from
the Gulf of Mexico north into southern Canada.
Other woods used by HTs are discussed in the
following paragraphs.
The redwood tree grows exclusively on the West
Coast. The age of these forest giants runs as high
as 3,000 to 4,000 years. They frequently grow to a
height of 350 feet, with a diameter of 25 feet or
MAPLE, especially eastern maple, is very hard
and is difficult to work. It varies in color from light
brown to white. Oregon maple (western soft maple)
is close-grained and reddish-brown in color. This
wood is mostly used in the manufacture of furniture
and tool handles. Oregon maple is also used for
certain projects that must endure heavy wear or that
are weak because of their shape or size. Maple will
outlast pine 8 to 1.
WHITE PINE is the best wood for making
simple patterns that are used less than 30 times and
that are under 2 feet in length. This softwood is
smooth, straight and even-grained, light, and warps
very little when properly seasoned. White pine that
is free from knots is the cheapest of lumber. With
sharp tools, you can cut and carve white pine almost
like soap. White pine takes a good coat of lacquer
or glue, but it chips or breaks easily. Its color
ranges from almost white to light yellowish-brown.
WHITE ASH is open-grained, elastic, and hard.
The color of the heartwood is light brown. The
sapwood is almost white.
In the West, the name white pine usually applies
to the native sugar pine that grows in northern
California and southern Oregon.
BLACK WALNUT grows in the eastern part of
the United States. It is very durable and very hard.
When used as pattern material, black walnut will
outlast pine 5 to 1.
PONDEROSA PINE is sometimes mistakenly
called sugar pine. It closely resembles the sugar
pine, but it is not good for some types of work such
as pattern work. It warps and shrinks a lot and has
more pitch than sugar pines.
HICKORY is the strongest, heaviest, and
toughest of all American woods. It is also flexible.
The color of hickory varies from brown to white.
OREGON PINE (Douglas fir) is of two
varieties, red and yellow. The yellow is the more
valuable of the two, being hard, strong, and very
durable—but difficult to work.
MAHOGANY is more durable and harder than
pine. Use it when 30 to 100 castings are required.
Also, use it for patterns having long or thin sections
or projections. Mahogany is strong, coarse-grained,
and warps very little. It is soft enough to cut and
nail easily, yet hard enough to stand a lot of wear.
Mahogany is difficult to plane or carve in the
CHERRY is brown in color, close-grained, and
very hard—but warps excessively. Cherry is a little
difficult to carve, but when used for small patterns,
it will outlast pine 5 to 1.
flat surface without full air circulation will usually
warp toward the exposed surface. The air draws
more moisture from the exposed surface than from
the underneath surface.
LIGNUM VITAE is excessively heavy, hard, and
resinous. Its color varies from light yellow to dark
greenish-brown—at times almost black. This wood
is native to tropical America, New South Wales, and
New Zealand.
The carpenter shop usually has overhead lumber
storage racks. The bulk of the lumber is stowed in
other parts of the ship because of space limitations
aboard a repair ship or tender.
TEAK is heavy, strong, and oily. It has a dark
color. It does not shrink, crack, or warp. Teak
comes from East India.
You should maintain a careful record of the
lumber used and on hand. If possible, at least 3
months’ supply should be on hand.
Care and Storage of Lumber
Lumber is a tool like the saw or plane and
should be considered as such. Store and care for
lumber properly. This will prevent it from becoming
water-soaked, rotted, or warped. The best way to
stow lumber is by stacking it on end in racks. This
way air can circulate around all the boards.
Circulation dries the wood evenly and reduces
Laminated lumber is made up of layers of wood
glued face-to-face (fig. 3-7). The parts glued
together to make laminated lumber may be thinly
sliced sheets of veneer or they may be sawed boards.
One advantage of laminated wood is that it can
be any desired thickness. Also, staggering the ends
of individual layers can produce timbers that are
much longer than solid timbers.
Room for storing lumber on end is hard to find
aboard ship. Lumber usually gets stored in the next
best manner. The accepted method is to store the
lumber horizontally. Separate the lumber by sizes.
Put the l-inch lumber together, the 1 1/2-inch
lumber together, and so on. When placing the
lumber in racks, you should place small strips or
battens about 1 inch thick across the boards about
6 feet apart. This will separate the boards and form
a space for the air to circulate around them. Air
circulation is important. A dressed board laid on its
Plywood (fig. 3-8) is thin layers of wood glued
face-to-face. It usually has the grain of each layer
at right angles to the next layer. Plywood alternates
grain each ply, and laminated wood never alternates
grain. Plywood always has an odd number of plies.
Veneered stock for furniture manufacture usually
has five layers. A thick layer called the core is in
the center. The layers that are glued on with the
grain running across are called cross bands. The
surface layers or faces are placed so their grain runs
parallel to the length of the panel.
One-quarter inch and one-eighth inch fir
plywood has only 3 plies. Plywood always has an
odd number of plies—up to 15. The standard size of
Figure 3-8.—Plywood.
Figure 3-7.—Laminated lumber.
plywood sheets is 4 feet wide by 8 feet long, though
smaller and larger sizes are available. Because of
the cross-grain effect, splitting plywood is very
difficult and shrinking and swelling are rare.
fiber faces that provide better painting surfaces and
better wearing qualities.
Because of the conditions of its manufacture,
plywood is dry when received. It should be stored
in a closed shed. For long storage, a heated storage
area is recommended.
The development of special glues and bonding
materials has made plywood highly resistant to
water. It was widely used during World War II and
is still in use in the Navy.
Plywood is commonly stacked in solid piles.
Under humid conditions, edges swell because of
exposed end grain. This swelling causes dishing,
especially in the upper panels of high piles. Reduce
dishing by placing strips between sheets of stacked
plywood. Use enough strips to prevent the plywood
from sagging between strips. Dry l-inch strips are
suitable for supporting plywood.
Two basic grades of plywood are interior and
exterior. Interior plywood is unreliable in wet
places. Exterior plywood will keep its original form
and strength when subjected to the elements. It is
suitable for permanent exterior use provided it is
properly protected from the elements.
plywood is branded or stamped on the edge with the
symbol EXT. or INT. More complete information
is stamped on the back of the plywood sheet. A
typical Douglas fir back stamp, with all symbols
explained, is shown in figure 3-9.
Hardboard is known by several trade names. It
is wood fibers separated, treated, and then subjected
to heat and heavy pressure. Hardboard is available
in thicknesses from 1/16 inch to 5/6 inch. The most
common size is 4-foot by 8-foot sheets, but other
sizes are available. Hardboard comes in a plain,
smooth surface or in several glossy finishes. Some
finishes imitate tile or stone. Use class B treated
hardboard where moisture resistance or strength is
required. Otherwise, class A hardboard is
Plywood is graded by the quality of the face
veneers. Grade A is the best. Grade D is the
poorest (fig. 3-9). Grading is based upon the
number of defects, such as knotholes, pitch pockets,
and splits. It also considers the presence of streaks,
discolorations, sapwood, shims, and patches in the
face of the panel. Plywood has resin-impregnated
Figure 3-9.—Typical Douglas fir back stamp.
The plain butt joint is the simplest and the one
most used by the HT.
An important skill to master is wood joinery. In
woodworking, joinery is the art of combining two or
more pieces of material into one. The purpose for
this procedure is to increase dimensions, strength, or
material alignment. Wood joinery includes the
manufacture of wood joints and the various devices
or methods used to fasten them together. These
methods include glue, screws, and brads.
The doweled joint is usually a plain butt joint
that has been given greater strength with wooden
dowels. Dowels also reinforce other joints such as
the miter and half lap.
When choosing a dowel for edge-to-edge use,
the dowel diameter should be one-third the
thickness of the stock you are jointing. Thus,
3/4-inch thick stock would require a 1/4-inch dowel.
A joint is only as strong as its weakest point.
This can be the joints if they are incorrectly made or
if you use the wrong joint. Correct joint usage and
proper construction can make the joint the strongest
point of the project.
The tongue-and-groove joint is stronger than the
butt or dowel joint. It is used for wood flooring.
The splined edge joint is a variation of the
tongue-and-groove joint. It is easier to make
because two matching grooves and a separate spline
replace the tongue. Minimal strength is gained if
the grain direction of the spline is parallel to the
edges, as shown in figure 3-11. A significant
strength gain results when the grain direction of the
spline is perpendicular to the edges.
There are four standard methods for joining
wood stock edge-to-edge. These methods are the
plain butt, dowel, tongue-and-groove, and splined
edge joints shown in figure 3-10.
The thickness of both the spline and tongue
should be one-third of the material thickness. The
width of the spline should be equal to twice the
material thickness, while the tongue width should be
the same as the thickness. For example, 3/4-inch
stock would require a spline measuring 1/4 inch
thick and 1 1/2 inches wide or a tongue measuring
1/4 inch thick and 3/4 inch wide (fig. 3-11).
Lap Joints
Lap joints are shown in figure 3-12. Plain lap
joints are used in all kinds of construction,
particularly if appearance is not a factor. The end
butt half lap is not as strong as the plain lap joint,
but it looks better and requires less space. The
corner half lap works well for framing buildings,
boxes, and cabinets. The cross lap joint joins the
spokes of a wheel pattern.
The scarf joint (fig. 3-13) is a special type of lap
joint that is used to join heavy timbers. For repair
purposes, the recommended slope is 1 in 12. The
cut should slant through the length of a piece of
wood 12 inches for every inch of depth or width.
The end butt joint with fishplates (fig. 3-14) is
useful for joining short members to make long
pieces. Secure the fishplates with nails, screws,
Figure 3-10.—Edge joints.
Figure 3-12.—Lap joints.
The gain joint (fig. 3-15) is a special kind of
dado joint. You use it when appearance is a factor.
Rabbet joints are often used with dadoes. They
are cut across or with the grain (fig. 3-16). Cut
rabbets with the circular saw dado head or with the
jointer. They can be cut by hand using special
rabbeting planes.
Dovetail Joints
Cabinetmakers and other skilled woodworkers
often use the dovetail joint (fig. 3-17). It is used
most often in joining the corners of furniture
drawers and chests because of its locking features.
Such joints are usually made with blind dovetails so
Figure 3-11.—Tongue and spline joints.
rivets, or bolts. Its main disadvantage is that it is
Dado, Gain, and Rabbet Joints
You would use the plain dado joint (fig. 3-15) to
make cabinets and shelves. You would usually cut
this joint with a dado head (cutters), which fits on a
circular saw. You also can make this cut by hand
using a backsaw or tenon saw and finish it with
chisels. Fasten this joint with glue, nails, or screws.
Figure 3-13.—Typical scarf joints.
Figure 3-14.—End butt joint with fishplates.
Figure 3-16.—Rabbet joints.
they cannot be seen from the outside of the
3-20) to shape the end of the abutting member to fit
the face of the first member.
Heavier construction that requires locking joints
call for single dovetails and half dovetails. The
single dovetail (dovetail key) is a good joint for
attaching a loose piece to a pattern. Dove tails
require accurate layout. Use a sharp knife edge to
mark the layout, not a pencil. Use a T-bevel to lay
out the angles. You can use the tenon saw to saw
out most of the waste and then finish the work with
a chisel.
Mortise-and-Tenon Joints
Good furniture has several mortise-and-tenon
joints (fig. 3-21). This joint appears weak, but when
glued it is very strong. It can be wedged, split, or
offset. You can’t go wrong with properly designed
and fitted mortise-and-tenon joints. Use the
slip-tenon joint the same way as a miter or corner
half-lap joint. Secure it with dowels, screws, bolts,
or nails and then glue it.
Box Corner and Miter Joints
Many commercial packing boxes are made with
the box corner joint (fig. 3-18). It cuts easily on the
circular saw with special dado heads.
One of the basic skills you must learn in
woodworking is to join pieces of wood to form tight,
strong joints. The two joined pieces are members.
The two major steps in joining members are layout
and cutting. Lay out the joints on the ends, edges,
or faces of the members. Then cut the members to
the required shapes for joining.
The miter joint (fig. 3-19) is used for picture
frames, boxes, panel frames, and other frames.
Glue the joints, and then fasten miter joints with
nails, brads, and corrugated fasteners.
The spline miter is better than the plain miter.
Cut it with the table saw and jig. Other miters
require more work and are used only on special
Coping Joints
When matching inside corner joints between
molding trim members, use the coping joint (fig.
Figure 3-17.—Dovetail joints.
Figure 3-15.—Dado and gain joints.
squaring a small board to dimensions by hand
should be the first lesson in woodworking. The six
major steps in the process are shown in figure 3-22.
Practice them until you learn to make a smooth,
square board with minimum planing.
Instruments used for laying out joints are the
combination square, the T-bevel, the marking gauge,
and a bench knife for scoring lines. For hand
cutting joints, use the backsaw, dovetail saw, coping
saw, and various chisels and planes.
You can cut all joints mentioned in this chapter
by hand or machine. Whatever the method you use
and whatever the type of joint, always remember the
following rule: To ensure a tight joint, always cut
on the waste side of the line, never on the line itself.
Cutting a groove on the waste side of the line with
a knife or chisel will help a backsaw get a smooth
Figure 3-18.—Box corner joint.
Cutting accurate joints requires square and true
stock. To square and true stock, you use a jointer
for trueing the edges and a surface planer to get
uniform thickness. Use a table or radial saw for
squaring the ends and cutting stock to the desired
length. Often, you will have to perform these
operations by hand.
Therefore, planing and
Figure 3-19.—Miter joints.
edges and end of each member. This line will
extend from the shoulder line on one edge to the
shoulder line on the opposite edge (fig. 3-23). Be
sure to gauge the cheek line from the face of each
member. If you gauge from both faces, the faces
will be flush after cutting the joint. The faces must
be flush regardless of whether or not the gauge was
set to exactly one-half the thickness. Too much
waste cut from one member offsets a lesser cut from
the other.
Figure 3-20.—A coping joint.
If you gauge from the face of one member and
the back of the other, and the gauge is not set to
one-half the thickness, the faces will be out of flush
by the amount of the error. A rule you should use
for half-lap joints is to always gauge the cheek line
from the face of the member.
Half-Lap Joints
For half-lap joints (fig. 3-23), the joining
members are usually the same thickness. For the
end butt half lap, measure off the desired amount of
lap from the end of each member. At this point,
use a combination square to guide and to score a
line all the way around the member. This is
squaring a line. For the corner half lap, measure
off the width of a member from the end of each
member. Square a line all the way around. These
are shoulder lines.
Next, make the shoulder cuts by sawing along
the shoulder line down to the cheek line. Saw from
the back of the lapping member and from the face
of the lapped member (fig. 3-23). Clamp a piece of
wood along the starting groove to steady the saw.
The cheek cuts (sometimes called the side cuts)
are next. Cut them along the waste side of the
cheek line. Clamp the member in the vise so it
leans diagonally away from you. With the member
in this position, you can see the end and the upper
edge. When the saw reaches the shoulder line on
Next, you should select the best surface of each
member and place it facing up. This is the face of
the member. The opposite surface is the back.
Mark the face of each member plainly. Next, set
the marking gauge to one-half the thickness of the
member. Score a line (called the cheek line) on the
Figure 3-21.—Mortise-and-tongue and slip-tenon joints.
Figure 3-22.—Planing and squaring to dimension.
Completing the shoulder cut will detach the
waste. The members should fit together with faces,
ends, and edges flush, or near enough to make flush
by a little paring with the chisel.
the upper edge, it will still be some distance away
from the shoulder line on the edge you can’t see.
Reverse the member in the vise, and saw exactly to
the shoulder line on that edge.
Figure 3-23.—End butt half-lap or comer half-lap joint.
A cross half-lap joint (fig. 3-24) between
members of equal cross-section dimensions is laid
out and cut as follows: If the members are of the
same length and they are to lap each other at the
midpoint, place them face-to-face with ends flush.
Then square a center line all the way around. To
test the accuracy of the center calculation, turn one
of the members end for end. If the center lines still
meet, the center location is correct.
In the cross half-lap joint, you should chisel the
waste out rather than saw it out. To make the
chiseling easier, remove as much stock as possible
with the saw first. Saw a series of kerfs between the
shoulder cuts. In chiseling, make a roughing cut
down to just above the cheek line with a firmer
chisel and mallet. Hold the chisel bevel down.
Finish off the bottom with a paring chisel while
holding the chisel bevel up.
When making a cross half-lap joint, you should
put the best wide surfaces up and mark each face
plainly. Lay off one-half the width of a member on
either side of the center lines; then, square the
shoulder lines all the way around. Again check for
accuracy by turning a member end for end. If the
shoulder lines meet, the layout is accurate. Next,
gauge one-half the thickness of a member. Do this
from the face of each member and score check lines
on the edges between the shoulder lines. Next,
make the shoulder cuts, sawing from the back of the
lapping member and from the face of the lapped
You can use a circular saw to cut half-lap
recesses and cross half-lap recesses. For an end
half-lap recess, set the table saw blade above the
table a distance equal to one-half the thickness of a
member. Place the member against the miter
gauge, set it at 90° to the saw blade, and make the
shoulder cut. Take out the remaining waste by
making as many recuts as necessary.
For a cross half-lap recess, you should proceed
as follows: Set the table saw blade or dado head so
its height above the table is equal to one-half the
thickness of a member. Then, place the member
against the miter gauge set at 90° to the saw blade
Figure 3-24.—Gross half-lap joint.
and make the shoulder cut. Then, reverse the piece
end for end and repeat the procedure to make the
opposite shoulder cut. Take out the remaining
waste between the shoulder cuts by making as many
recuts as necessary.
the waste side of the line. Start the saw and bring
the piece into light contact with it. Then stop the
saw. Look at the stock to make sure the cut will be
on the waste side of the line. Adjust the fence if
Grooved Joints
When the fence position is exact, make the cut.
Reverse the piece and proceed to set and test as
before for the cut on the opposite side of the
groove. Make as many cuts as necessary to remove
the waste stock between the side kerfs.
A groove is a three-sided recess running with
the grain. A similar recess running across the grain
is a dado. A groove or dado that does not extend
all the way across the piece is a stopped groove or
a stopped dado. A stopped dado is also known as
a gain (refer to fig. 3-15).
Grooving with the dado head is the same as
dadoing, with one exception. The dado head builds
up to take out all or most of the waste in a single
cut. The two outside cutters alone will cut a groove
1/4 inch wide. Inside cutters vary in thickness from
1/16 to 1/4 inch.
A two-sided recess running along an edge is a
rabbet (refer to fig. 3-16). Dadoes, gains, and
rabbets are not actually grooves, but the joints are
called grooved joints.
The circular saw can cut a stopped groove or
stopped dado. You can use either a saw blade or a
dado head as follows: Clamp a stop block to the
rear of the table if the groove or dado stops at only
one end. (This will stop the piece from feeding
when the saw has reached the place where the
groove or dado is supposed to stop.) If the groove
or dado stops at both ends, clamp a stop block to
the rear of the table and a starting block to the
front. Place the starting block so the saw will
contact the place where the groove is supposed to
start when the infeed end of the piece is against the
block. Start the cut by holding the piece above the
saw. Place the infeed end against the starting block
and the edge against the fence. Lower the piece
gently onto the saw blade. When the piece contacts
the tabletop, feed it through to the stop block.
Grooves on edges and grooves on faces of
narrow stock can be cut by hand with the plow
plane. The matching plane will cut a groove on the
edge of one piece. It also cuts a tongue to match it
on the edge of another. You can cut a dado by
hand with the backsaw and chisel. Use the same
method used to cut a cross half-lap joint by hand.
Saw rabbets on short ends or edges by hand with
the backsaw.
Cut a long rabbet by hand with the
rabbet-and-fillister plane by using the following
procedure: First, be sure that the side of the plane
iron is exactly in line with the machined side of the
plane. Then, set the width and depth gauges to the
desired width and depth of the rabbet.
NOTE: Be sure to measure the depth from the
edge of the plane iron, not from the sole of the
plane. If you measure from the sole of the plane,
the rabbet will be too deep by the amount that the
edge of the iron extends below the sole of the plane.
Next, clamp the piece in the vise. Hold the
plane perpendicular, press the width gauge against
the face of the board, and plane down with even,
careful strokes. Continue until the depth gauge
prevents any further planing.
When you are cutting a rabbet, the cut into the
face of the piece is the shoulder cut. The cut into
the edge or end is the cheek cut. Make the
shoulder cut first. Set the saw to extend above the
table a distance equal to the desired depth of the
shoulder. Set the fence a distance away from the
saw equal to the desired depth of the cheek. Be
sure to measure this distance from a sawtooth set to
the left of, or away from, the ripping fence. If you
measure it from a tooth set to the right of, or
toward, the fence, the cheek will be too deep.
Cut a groove or dado on the circular saw as
follows: Lay out the groove on the end of the
wood. For a dado, lay out the edge. Set the saw to
the depth of the groove above the table. Set the
fence so the saw will cause the first cut to run on
Place the face of the piece that was down for
the shoulder cut against the fence and make the
cheek cut. Make the cheek cut with the saw at the
same height as for the shoulder cut if the depth of
the shoulder and the depth of the cheek are the
bare-faced tongue. The dado and rabbet joint (fig.
3-25) is another joint often used in making boxes,
drawers, and cabinets.
same. Change the height of the saw if the depth of
the cheek is different.
By using the dado head, you can cut most
rabbets in a single cut. First, build up a dado head
equal in thickness to the desired width of the cheek.
Next, set the head to protrude above the table a
distance equal to the desired depth of the shoulder.
Clamp a l-inch board to the fence to serve as a
guide for the piece. Set the fence so the edge of
the board barely contacts the right side of the dado
head. Set the piece against the miter gauge that is
set at 90° to the saw blade. Now hold the edge or
end to be rabbeted against the l-inch board and
make the cut.
The housed lock-joint (fig. 3-26) is a type of
dado and rabbet joint. Note that the rabbeted piece
is reversed. The dadoed piece extends beyond the
rabbeted piece. This joint is used extensively in the
pattern shop for manufacturing special wooden
foundry flasks. The dadoed piece extends to form
handles for the flask.
Dovetail Joints
The dovetail joint (refer to fig. 3-17) is the
strongest of all the woodworking joints. However,
its construction requires a lot of work; therefore,
you will use dovetail joints only when working on
finer grades of furniture and cabinet work.
On jointers, a rabbeting strip on the outboard
edge of the outfeed table depresses for rabbeting.
The strip is outboard of the end of the cutterhead.
To rabbet on a jointer, you depress the infeed table
and the rabbeting strip the depth of the rabbet
below the outfeed table. Set the fence the width of
the rabbet away from the outboard end of the
cutterhead. The unrabbeted part feeds onto the
rabbeting strip when the piece feeds through.
A joint containing only a single pin is a single
dovetail joint. A joint containing two or more pins
is a multiple dovetail joint. A joint in which the
pins pass all the way through the tail member is a
through dovetail joint. A joint in which they pass
only part way through is a blind dovetail.
Various combinations of the grooved joints are
used in woodworking. The well-known
tongue-and-groove joint is actually a combination of
the groove and the rabbet. The tongued member is
simply a member rabbeted on both faces. In some
types of panel work, the tongue is made by
rabbeting only one face. A tongue of this kind is a
The simplest dovetail joints is the half-lap
dovetail joint (fig. 3-27). This joint is first laid out
and cut like an ordinary end half lap. The end of
the lapping member is laid out for shaping into a
dove tail as follows:
Set the T-bevel to 10°. This is the correct
angle between the vertical axis and the sides of a
dovetail pin or tail. You can set the bevel with a
protractor or with the protractor head on the
Figure 3-25.—Dado and rabbet joint.
Figure 3-26.—Housed lock-joint.
Figure 3-27.—Dovetail half-lap joint.
Figure 3-29.—Making a half-dovetail joint.
combination square. If you don’t have either of
these, use the method shown in figure 3-28.
occupy, and score the outline of the recess. Then
saw and chisel out the recess. Remember to saw on
the waste side of all lines.
Select a board with a straight edge, square a
line across it, and lay off six equal lengths on the
line as shown. From the sixth mark, lay off one
length perpendicular to the right. A line drawn
from this point to the starting point of the first line
drawn will form a lo-degree angle with that line.
To make a multiple-dovetail joint, you lay out
the end of the tail member as shown in figure 3-30.
The strongest type of dovetail joint is one in which
the pins and tails are the same size. For ease in
cutting, the pins are usually somewhat smaller than
the tails (as shown). To make a multiple-dovetail
joint, you first determine the number of pins and
the size you want to make each pin. Then, lay off
a half-pin from each edge of the member. Next,
locate the center lines of the other pins at equal
intervals across the end of the piece. Then, you lay
Lay off this angle from the end corners of
the lapping member to the shoulder line (fig. 3-29).
Saw out the waste as shown. The lapping member
now has a dovetail on it. Place this dovetail over
the other member, in the position it is supposed to
Figure 3-28.—Laying off a 10-degree angle for a dovetail
Figure 3-30.—Laying out pin member for through
multiple-dovetail joint.
Box Corner and Miter Joints
The box corner joint is the same as a multiple
dovetail with one exception—the 10-degree angle
(refer to fig. 3-18). A miter joint (refer to fig. 3-19)
is made by mitering the ends or edges of the
members that are to be joined. The angle of the
miter cut is one-half of the angle formed by the
joined members. In rectangular frames, door
casings, boxes, and the like, adjacent members form
a 90-degree angle. The correct angle for mitering is
45°. For members that will form an equal-sided
figure with other than four sides (such as an octagon
or a pentagon), you need to calculate the correct
mitering angle. Do this by dividing the number of
sides the figure will have into 180, as shown in
figure 3-33.
Figure 3-31.—Chiseling out waste in a through
multiple-dovetail joint.
off the outlines of the pins at 10° to the center lines.
Determine the depth of the shoulder line by the
thickness of the tail member.
You cut out the pins by sawing on the waste
sides of the lines and then chisel out the waste.
You should chisel halfway through from one side, as
shown in figure 3-31. Then turn the member over
and chisel through from the other side.
You can miter members in a wooden or metal
miter box or on the circular saw by setting the miter
gauge to the desired angle. You can edge miter
members to any angle on the circular saw by tilting
the saw.
When you have finished cutting out the pins, lay
the tail member flat. Set the ends of the pins in
exactly the position they are to occupy (fig. 3-32).
Score the outlines of the pins, which will, of course,
also be the outlines of the tails. Square lines across
the end of the tail member. Saw and chisel out the
waste between the tails.
Abutting surfaces of end-mitered members do
not hold well when merely glued. You need to
reinforce them. A good reinforcement for a joint
between end-mitered members is the slip feather.
This joint is a thin piece of wood or veneer glued
into a kerf cut in the thickness dimension of the
Figure 3-32.—Marking the tail member.
line left by the 45-degree miter cut. The ends of the
abutting members will then match the face of the
other member as shown in view D.
Mortise-and-Tenon Joints
The mortise-and-tenon joint is mostly used in
furniture and cabinet work. In the blind
mortise-and-tenon joint (refer to fig. 3-21), the
tenon does not penetrate all the way through the
mortised member. When the tenon penetrates all
the way through, it is a through mortise-and-tenon
joint. Besides the ordinary stub joint (fig. 3-37, view
A), there are haunched joints (view B) and
table-haunched joints (view C). Haunching and
table-haunching increase the strength and rigidity of
the joint.
lay out an ordinary stub mortise-and-tenon joint
using the following steps:
1. Mark the faces of the members plainly.
2. Lay off the desired length of the tenon.
3. Square the shoulder line all the way around.
Figure 3-33.—Mitering angles.
4. Then, lay off the total width of the tenon
member on the mortise member, as shown in figure
joint. (See fig. 3-34 for a simple jig to use when
making the kerf cut.) Saw about halfway through
from the outer to the inner corner. Apply glue to
both sides of the slip feather, and push the slip
feather into the kerf (fig. 3-35). Clamp it tight and
allow the glue to dry. After it has dried, remove the
clamp and chisel off the protruding portion of the
slip feather.
5. Determine the thickness of the tenon. It is
usually between one-third and one-half the thickness
of the mortise member.
6. Use a marking gauge to mark two lines (fig.
3-38). If the faces of the members are to be flush,
use the same gauge setting to score a double line on
the mortise member. Remember to gauge from the
face of the member. If the face of the tenon
member is to be set back from the face of the
mortise member, you should increase the mortising
gauge setting by the amount of the setback.
Coping Joints
Inside corner joints between molding trim
members are usually made by placing the end of
one member against the face of the other. Figure
3-36 shows the method of shaping the end of the
abutting member to fit the face of the other
members. First, saw the end of the abutting
member square. Do this as you would an ordinary
butt joint between ordinary flat-faced members.
Then, miter the end to 45°, as shown by views A
and B of figure 3-36. Set the coping saw at the top
of the line of the miter cut. Hold the saw at 90° to
the lengthwise axis of the piece. Saw off the
segment as shown in view C. Closely follow the face
7. Last, lay off from the end of the mortise
member and from the matching edge of the tenon
member. Lay off by the amount of end stock that
is to remain above the mortise.
NOTE: You wouldn’t need this last step of the
layout for a slip-tenon joint, like the one shown in
figure 3-21.
Figure 3-34.—Kerf jig for mitered joints.
joint, use a depth gauge. Use of the depth gauge
prevents the drill from boring below the correct
depth of the mortise.
JOINTS.—You can cut tenons by hand with the
backsaw by using the same method described for
cutting corner and end half-lap joints. You can cut
mortises by boring a series of holes slightly smaller
than the width of the mortise. Then, you chisel out
the remaining waste. For a blind mortise-and-tenon
Look at figures 3-39 and 3-40 as you read the
following steps on using a circular saw to cut tenons.
Figure 3-36.—Making a coping joint.
4. Set the saw the depth of the cheek above the
5. Set the fence the width of the shoulder away
from the saw. Then make the cheek cuts, as shown
in figure 3-40. To steady the stock against the
fence, use a feather board like the one shown
clamped to the table. To maintain the stock
upright, use a push board, like the one shown in
figure 3-40.
Figure 3-35.—Slip feather reinforcement.
1. Make the shoulder cuts first.
2. Set the saw the depth of the shoulder above
the table.
You can also use a dado head to cut tenons.
Use the same method described before for cutting
end half-lap joints.
3. Set the rip fence the length of the tenon
away from the saw. Remember to measure from a
sawtooth set to the left. Make the shoulder cuts, as
shown in figure 3-39.
A hollow-chisel mortising machine cuts mortises
mechanically. The cutting mechanism on this
machine consists of a boring bit encased in a square
hollow steel chisel. As the mechanism presses into
Figure 3-37.—Mortise-and-tenon joints. A. Stub. B. Haunched. C. Table-haunched.
Figure 3-40.—Using a feather board and push board to
steady stock when cutting a tenon cheek.
Figure 3-38.—Layout of a stub mortise-and-tenon joint.
the wood, the bit takes out most of the waste. The
chisel pares the sides of the mortise square. Chisels
come in various sizes with bits to match.
Fasten mortise-and-tenon joints with glue and
additional fasteners as required. One or more wood
or metal dowels may be driven through the joint to
give strength to the joint.
Plywood panels are installed in frames to make
parts of doors, partitions, bulkheads, and many
other items. The panels can be installed by several
methods. Four commonly used methods are shown
in figure 3-41. Notice in figure 3-41, views A and B,
Figure 3-39.—Gutting a square-shouldered tenon.
Figure 3-43.—Comer butt joint for table legs.
Figure 3-42 shows the layout and design for
mortise-and-tenon joints. Mortise-and-tenon joints
join the table rails to the legs (fig. 3-43) and secure
the stretcher to the lower end rails. An alternate
method of securing the legs to the rails is by corner
plates and lag screws. Using this method, the legs
tighten easily when they become loose. They also
remove easily for storage or moving.
Figure 3-41.—Panel construction.
how a groove and rabbet set the panel into the rails
and stiles. Join the rails and stiles by using dowels,
miter joints, half-lap joints, or mortise-and-tenon
Standard methods of making a table are shown
in figures 3-42 through 3-46. Make desks in much
the same manner but with the addition of panels
and more drawers.
Make drawers for tables and desks by the
method shown in figure 3-44. You will find it easier
to make drawers by this method than by making
them with dovetail joints. However, dovetail joints
are better and should be used on jobs made of fine
cabinet woods. Use blind dovetails for the front
corners of drawers made for such furniture.
Figure 3-42.—Mortise-tenon layout and design.
Figure 3-44.—Simple drawer construction.
powder mixed with another solution. It is a
water-resistant glue that works well on hardwoods.
It is a cold-working glue that sets within 24 hours at
room temperature (70°F). Urea resin glues set and
harden by the condensation of the resin.
Vinyl resin glue is a synthetic thermoplastic
white liquid. It requires no mixing or heating
before use. This glue comes ready to use and can
be applied at temperatures above 50°F. The initial
setting of the glue takes less than 30 minutes. A
strong bond will occur in less than 1 hour for
ordinary work. In addition, this glue is compounded
to reduce wear on cutting tools. It also has a glue
line that is practically colorless. For general
construction, vinyl resin glue has replaced all glues
that require heating, cooking, or mixing.
Figure 3-45.—Standard table construction.
Pointers on Using Glue
Tabletops usually fasten to the upper rails (fig.
3-45) by one of the six standard methods shown in
figure 3-46. You will probably use the cleat more
than any of the others. Fasten the cleat screws to
the rail first so it is about 1/16 inch below flush.
Then, the screws going into the top will pull the top
down tight and snug.
Prepare and use each type of glue in a specific
manner. Instructions and safety precautions are
always given on the label of the container, or on the
MSDS for the glue. You should study these
carefully before trying to use any glue. Certain
rules should be followed in the application of all
The wood should be room temperature (70°F).
If the wood is cold, the glue next to the wood chills
and sets before it has penetrated the pores of the
joint. If the wood is hot, the water in the wood will
expel, causing the joint to warp. Glues give best
results when the wood is at room temperature.
Many kinds of fasteners hold wood together.
These include glue, nails, screws, bolts, and special
Squeeze or rub excess glue out of a joint before
applying pressure. Always apply pressure as quickly
as possible after spreading the glue. This prevents
the glue from setting before the excess can be
squeezed out. The greater the pressure applied, the
stronger the joint will be.
The two most commonly used glues in today’s
pattern shop are urea resin glue and vinyl resin
(white) glue.
Urea resin glue is a synthetic compound that
comes either in a powder mixed with water or a
NOTE: Do not apply so much pressure that the
wood crushes.
If possible, the pressure should be at least 100
psi. Squeezing out too much glue is impossible.
Clamps alone produce this pressure, but they do not
distribute the pressure evenly. To get a joint with
maximum strength, you should use plates between
the clamps and the wood.
Figure 3-46.—Securing rails to tabletops.
After proper arrangement, use some system of
marking the pieces of stock. This is so they will not
be disarranged during the gluing-up process. Apply
a good coat of glue to the surface of the piece of
stock lying face up. Place one of the other pieces of
stock face-to-face with the glued surface. Rub back
and forth or in a circular motion. Exert as much
down pressure as possible. This spreads the glue
evenly throughout the joint and helps prevent air
bubbles. In addition, a certain amount of glue is
driven into the pores of the wood. The glued
surfaces are pulled closer together. Repeat the
preceding gluing operations until all pieces are
Methods of Applying Glue
When you need thicker or wider material but it
is not available, you will have to glue several pieces
of material together. The two principal methods
used for gluing wood stock are face-to-face gluing
and edge-to-edge gluing.
In face-to-face gluing, first determine the sizes
of stock needed. Then, you should decide what
available stock can be glued up to produce the
required size. Remove enough lumber from the
rack to do the job. Saw the lumber to the required
lengths. Dress one face and one edge of each piece
of material on the jointer. Dress the material to the
proper thickness in the planer. Rip the pieces to
the proper width in the circular saw. Adjust the
hand clamps to an approximate jaw opening. Lay
the stock on the bench and fit each clamp loosely
over the stock. Then place them in a spot where
they can be easily reached.
Position clamps and tighten glued-up stock as
shown in figure 3-47. Place clamp A in a position
so that when the clamps are all in place, the space
between them will be somewhat equal throughout
the length of the material. Keep lower clamp
spindle M at least 1/2 inch above the surface of the
material. Tighten up on spindle M and release
spindle N until a fair amount of pressure is on that
part of the jaws near M. Next, turn spindles M and
N until the entire face of jaw F is exerting an even
pressure on the face of the material. Use enough
force to squeeze excess glue from the joints of the
glued-up stock and draw all surfaces tightly together.
Place the stock in the desired gluing position.
Alternate in relation to the growth rings. The
warpage of each piece offsets the warpage of the
one next to it if this arrangement is followed. Also,
arrange the pieces so the grain of their respective
surfaces runs in the same direction. Otherwise,
difficulties may arise later when dressing the job to
proper thickness. Planing with the grain on one
part of the surface may prove to be the wrong
direction for an adjacent area.
Adjust and tighten clamp B just like clamp A.
As each clamp is added, the glue is forced along, as
well as out of, the joint. If the ends are clamped
first, a large amount of glue is trapped in the
Figure 3-47.—Face-to-face gluing.
gluing. Set the clamp jaw openings to suit the width
of the assembled pieces of stock. Allow for blocks
on the edges of the material to prevent marring.
Make two jig blocks for each of the bottom clamps
(fig. 3-48) to hold the clamps upright during the
gluing operations. Again, note the arrangement of
pieces so the annual ring growth will tend to offset
warpage. Be sure the direction of the grain is the
same in all the pieces to be glued.
middle. This is especially true when you are gluing
up wide pieces of material. Next, turn the stock
completely over on a table or bench so it rests on
the ends of clamps A and B. Place clamps C and
D, and adjust the same as clamps A and B.
NOTE: Clamping the midsection of the material
first will give the excess glue squeezed out of the
joint more outlets.
Place glue on the edges of the boards you are
joining. Rub the stock together to spread the glue
evenly and force out any air bubbles. If the ends of
the joints come apart before tightening the clamps,
use pinch dogs to hold the boards together
temporarily. Put the middle clamps in place with
the blocks in front of the jaws. Adjust and tighten
them. Then adjust and tighten the clamps on the
ends, squeezing out all excess glue.
Now examine the job carefully to see that all the
clamps are properly set and that all the glued joints
have been properly drawn up. Remove the job to a
convenient spot where it will be out of the way until
needed. If the job stays on the bench, excess glue
squeezed from the joint will stick to the bench top.
You should clean all waste glue from the top of the
When the glue has jelled, remove it with a glue
scraper. Then wipe the surface with a piece of cloth
dipped in hot water. If it is a rush job, the clamps
may be removed in 4 hours. However, the joints
cannot be guaranteed to hold if the clamps are
removed too soon. Best results will result from
clamps left on for 12 hours. You should plan
construction of the job to provide time for good
results in gluing operations.
Inspect the clamps every few hours to make sure
the stock is not warping. If any of the edges pull
apart before the glue has dried, adjust the clamps to
apply equal tension throughout.
Fastening materials such as nails, brads, dowels,
and corrugated fasteners work in combination with
glue in pattern construction. Many of the materials
used in the HT rating are the same as those found
in other woodworking trades. Nails provide the
least holding power, screws provide better, and bolts
provide the best holding power of all. Wood screws
may be combined with glue and paper in parted
pattern turning. Use dowels for the alignment of
The edge-to-edge method of gluing up stock has
two purposes. It is used most often to get material
that will be thin in comparison with its width. Use
this method to glue up material that has to be wider
than any on hand.
In edge-to-edge gluing, select, dress, and rip the
material the same way as you did for face-to-face
Figure 3-48.—Edge-to-edge gluing.
parted patterns and of loose pattern parts. A
description of these fasteners is given in the
following paragraphs.
size, shape of head, type of point, and finish. Nail
sizes are described by the term penny. The penny
sets the length of the nail (one penny, two penny,
and so on) and is the same for all types. The
approximate number of nails per pound varies with
the type and size. The wire gauge number varies
with type. Figure 3-49 provides the information
related to the term penny for each nail type
Nails and Brads
There are many types of nails, which are
classified according to use and form. They vary in
Figure 3-49.—Types of nails and nail sizes.
The finish nail (fig. 3-50, view C) is made from
finer wire than either the common wire or box nail.
Its length per penny size is the same. The finish
nail has a small head that may be set below the
surface of the wood. The small hole that remains
may be puttied or waxed over. You should use
finish nails where appearance is important.
referenced in this section. The d next to the
numbers in the size column is the accepted
abbreviation of the word penny, as used in nail
sizing. It reads two penny, three penny, and so on.
A few rules should be followed when you use
nails. For maximum holding power, a nail should
be at least three times as long as the thickness of
wood it is to hold. Two-thirds of the length of the
nail is driven into the second piece for proper
anchorage. One-third provides the necessary
anchorage of the piece being fastened. Nails should
be driven at a slight angle toward each other. Place
them carefully to provide the greatest holding
power. Nails driven with the grain do not hold as
well as nails driven across the grain. A few nails of
proper type and size, properly placed and driven,
will hold better than many nails poorly placed.
Nails are the cheapest and easiest fasteners to use.
The duplex nail (fig. 3-50, view D) is a
temporary fastener so it has two heads. The lower
head, or shoulder, is driven securely home to give
maximum holding power. The upper head projects
above the surface of the wood to make it easy to
The wire gauge brad (fig. 3-50, view E) comes in
several gauges for the same length of brad. It
ranges in length from 3/8 inch to 6 inches. It is the
most suitable brad for pattern work. Remember
that for brads, the higher the gauge number, the
smaller the body diameter. Length and wire gauge
identify its size. For example, 1–12 means 1 inch
long and made of 12-gauge wire (0.105 inch), while
1 1/2—15 means 1 1/2 inches long and made of
15-gauge wire (0.072 inch).
The common wire nail (fig. 3-50, view A) has a
flat head. It ranges in size from 2d (1 inch long) to
60d (6 inches long). The box nail (fig. 3-50, view B)
has the same length per penny size as the common
wire nail. It has a lighter head and smaller
diameter. In structural carpentry where appearance
is not important, you should use both the common
wire and box nail.
Wood Screws
Several factors dictate the use of wood screws
rather than nails and may include the type of
material being fastened and the holding power
requirements. Other factors could be the finished
appearance desired and limits to the number of
fasteners used. Using screws rather than nails is
more expensive in time and money, but their use is
often necessary to meet specifications.
The main advantages of screws are they provide
more holding power and tighten easily to draw the
items fastened securely together. They are also
neater in appearance if properly driven and may be
withdrawn without damaging the material. The
common wood screw is made from unhardened
steel, stainless steel, aluminum, or brass.
Unhardened steel or brass screws are normally used
in the pattern shop. Wood screws are threaded
from a gimlet point for about two-thirds the length
of the screw. They have a slotted or Phillips head
designed to be driven by a screwdriver.
Wood screws (fig. 3-51) are classified according
to head style. The most common types are flat
head, oval head, and round head, both in slotted
and Phillips heads.
Figure 3-50.—Nails and brads.
Figure 3-51.—Types of wood screws and nomenclature.
To prepare wood for receiving the screws, you
bore a pilot hole the diameter of the screw in the
piece of wood to be fastened (fig. 3-52). Then bore
a smaller starter hole in the piece of wood that is to
act as anchor to hold the threads of the screw. Drill
the starter hole with a smaller diameter than the
screw threads. Go to a depth one-half or two-thirds
the length of the threads to be anchored. The
purpose of this careful preparation is to assure
accuracy in the placement of the screws. It also
reduces the chance of splitting the wood and
reduces the time and effort required to drive the
Figure 3-52.—Sinking a screw properly.
The proper name for lag screws (fig. 3-51) is
lag-bolt wood screw. Building construction often
requires you to use these screws. Lag-bolt wood
screws are longer and much heavier than the
common wood screw and have coarser threads. The
threads extend from a cone or gimlet point slightly
more than half the length of the screw.
Square-head and hexagon-head lag screws are
always externally driven, usually by a wrench. They
are used when ordinary wood screws would be too
short or too light.
Properly set slotted and Phillips flat-head and
oval-head screws are countersunk enough to permit
covering the head. Round-head screws are driven
so the head is firmly flush with the surface of the
wood. The slot of the round-head screw is parallel
to the grain of the wood.
Wood screws come in sizes that vary from 1/3
inch to 6 inches. Screws up to 1 inch in length
increase by eighths. Screws from 1 to 3 inches
increase by quarters. Screws from 3 to 6 inches
increase by half inches. Screws also vary in shaft
size. Proper nomenclature of a screw is shown in
figure 3-51. This includes the type, material, finish,
length, and screw size number. The screw size
number shows the wire gauge of the body, drill, or
bit size for the body hole. It also shows drill or bit
size for the starter hole. Tables 3-3 and 3-4 provide
size, length, gauge, and applicable drill and auger bit
sizes for screws.
HTs use dowels to assemble and hold loose
parts of a pattern in proper relation to each other
while ramming up the pattern. Dowels often
reinforce glued joints and delicate parts of a job.
Wood dowels are round wooden pins made from
straight-grained maple or birch. The diameters
commonly used in the shop range from 1/8 to 1
inch, in 1/8-inch increments.
Table 3-3.—Screw Sizes and Dimensions
Metal dowels (usually brass) are sometimes
used. They do not damage easily, and they do not
absorb moisture from the molding sand.
Metal dowels (fig. 3-53) are self-centering. The
lower portion of the threaded end locates its own
center in the bored hole. It also holds the dowel to
Table 3-4.—Drill and Auger Bit Sizes for Wood Screws
Corrugated Fasteners
Corrugated fasteners are metal strips bent into
many W shapes. These fasteners are used to butt
two pieces of wood together. One- half the
corrugated fastener goes on the first piece, the other
half goes on the second. They are driven into the
wood like a nail; but unlike a nail, they are not
intended to be removed. The wood is destroyed if
you try to remove a corrugated fastener. The most
common application for corrugated fasteners is for
holding together picture frames. The fastener is
occasionally placed on the back side of the wood,
but normally it is used like a slip feather.
The sequence of steps you should follow to
complete a project is discussed in the following
sections. A brief list of the steps follows. Sand the
pattern to remove tool marks and ridges before it
receives its final protective coating. Add fillets and
include identification markings. Set rapping and
lifting plates into the pattern.
Figure 3-53.—Dowels and dowel keys.
its center as the threads cut their way into the wood.
The thread depth keeps the dowel tight. The male
and female parts fit within 0.001 inch.
You can easily insert or remove the metal dowel
from the pattern by using a dowel key (fig. 3-53).
Table 3-5 lists the dowel number size, the diameter
of the dowel pin, and the recommended drill
You need to use the correct sandpaper for the
sanding job on which you are working.
Sandpaper is graded by the coarseness or
fineness of the abrasive particles used on the paper.
The grade is marked by a number on the back of
the sandpaper. Table 3-6 shows sandpaper sizes and
their suggested uses. Sandpaper usually comes in
9-inch by 11-inch sheets. For machine sanders, it
comes either in rolls or cut to fit the machine.
Table 3-5.—Drill Sizes for Metal Dowels
Dowel No.
Dowel Diameter
Drill Size
Proper storage of sandpaper is important.
Never store it in an area that is too damp or too
dry. Moisture loosens the abrasive material, while
excessive dryness makes the paper too brittle.
Hand and lathe sanding are the two methods of
finish sanding that you will routinely use. When you
first started your pattern, you rough sanded pattern
parts on power sanders made to remove large
amounts of wood quickly. Finish sanding requires
the careful removal of small amounts of wood in
selected spots.
Table 3-6.—Abrasive Recommendations
Paints and
Hard tough
minerals and
Hard brittle
mineral and
Hard metals
Soft metals
Hard wood
compositions (aluminum
Soft wood
{ 80-120
{ 100-180
Wet paper
"A" weight
{ 80-120
cloth in oil
Wet paper
"A" weight
{ 80-120 (silicon
{ 60-100 (aluminum
{ 50-80
{ 40-60
{ 36-50
Wet paper
“A” wight
{ 2 1/2- 1 1/2
{ 36-60
{ 240-400
{ 150-320
{ 220-320
or crocus
{ 150-320
{ 120-180
{ 60-100
Wet paper
“C” wight
{ 120-220
Wet paper
“A” wight
{ 240-600
{ 2-1
{ 1/2-2/0
{ 3/0-5/0
Redwood and some pines have a marked
difference in hardness between the soft and hard
portions of their growth rings. The abrasive on the
sandpaper removes the softer portion of the grain
quite rapidly when sanding is done with the grain on
this type of wood. The harder grain portions offer
Normally, you sand the finished surfaces of
cabinet and jointer work with the grain. Sanding
with the grain avoids scratches that might spoil the
natural appearance of the wood grain.
more resistance to the abrasive. Instead, they tear
the abrasive from the paper. This loose material, in
turn, wears the softer portions of the wood. This
produces a washboard surface that is not acceptable
for a pattern. When the same woods are sanded
across the grain, the abrasive material rapidly cuts
tiny chips out of the hard fiber walls. The entire
abrasive face of the sandpaper dulls evenly. It
cannot remove the soft grain portion any faster than
the reduction of the hard fibers will permit.
method of sanding is for surfaces for which a
sanding block will not work. Avoid sanding too long
in one spot. This could change the dimensions of a
For sanding flat surfaces, you should select a
sheet of sandpaper that is just coarse enough to
dress the surface free of tool marks without cutting
the surface too rapidly. Then, tear or cut a sheet of
sandpaper into four equal parts since it is too large
for the average-size job.
The principal purpose of sanding a finished or
lacquered surface is to remove any roughness that
may be present without removing the finish. The
pressure exerted on the sandpaper should never be
greater than that necessary to get satisfactory
results. Also, use as fine a grade of sandpaper as
the job will permit.
After you have finished sanding with a folded
sandpaper, finish sanding by tearing off a narrow
strip of sandpaper. Use it shoeshine fashion. Use
a fine grade of sandpaper when you are finishing
small jobs. Use coarser grades on larger work.
Make a sandpaper block and fold one of the
pieces of sandpaper around it. Sand the surface by
moving the block back and forth across the grain
with long strokes. Move along the surface from one
end of the material to the other. Do not sand in
one spot. Try to remove an equal amount from all
parts of the surface during each sanding motion.
Brush the surface free of wood dust and loose
abrasives. Examine the surface for tool marks. If
they are not all removed, repeat these sanding
operations until you get the desired results.
Complete sanding of the surface with a fine grade of
sandpaper, then brush the surface clean.
Look at the finished surface to see if it is fully
dry before trying to sand it. Select a sheet of
sandpaper of proper grade for the job to be done.
Sand the surface very lightly at first. Use strokes
that are as long as possible. Do no more sanding
than is necessary to produce a smooth surface.
Also, examine the sandpaper often to see if any part
has become gummed with finish material. If it has,
do not use that part of the sandpaper any longer.
It will scratch the surface of the job.
When sanding straight narrow edges, sand with
the grain of the wood. Most people use a rocking
motion with a sanding block when cross-grained
sanding on narrow edges. The rocking motion
produces a rounded surface.
Sanding work in a lathe should be done very
carefully because the dimensions of the job may
alter. Carefully turn the job to a smooth finish so
only minor sanding is necessary to finish the surface.
Use a fine grade of sandpaper (120 or 150) on the
average-size job. Always remove the tool rest from
the lathe before sanding a job.
When sanding concave surfaces, use a
round-faced block. Do as much cross-grained
sanding as you can. Start each sanding stroke at the
top edge of the concave surface and push toward
the bottom. Do not sand on the back stroke. You
may pass over the edge and knock the corner over.
Clean the surface often during sanding and look for
tool marks. Finish the surface with a fine grade of
In sanding irregular surfaces, the usual
procedure is to tear the sandpaper sheet into four
equal parts. Fold each part to get three separate
surfaces. As one surface of the paper becomes dull,
turn the paper over until the entire piece has been
used. Hold the paper as shown in figure 3-54. This
Figure 3-54.—Holding folded sandpaper.
Figure 3-57.—Sanding a concave faceplate pattern.
Figure 3-55.—Sanding a lathe job.
proper angle so all angles, edges, or shoulders keep
their designed shapes (fig. 3-56).
If the job is small, use a half sheet. For a large
job, use the whole sheet folded twice. Apply the
sandpaper lightly (fig. 3-55), moving it along the
surface of the job. Do not sand in one spot. When
sanding the ends of the job, use a narrow strip of
sandpaper. Fold the sandpaper between your
fingers in the shape of the sanding surface. Then
hold it lightly against the stock. Rotate it at the
When sanding a concave faceplate pattern, you
should start by tearing a suitable piece from a sheet
of sandpaper. Fold it over twice. Bend the paper
a few times to make it pliable. Then, sand the job
as shown in figure 3-57. Do not knock off the sharp
corners on the face of the bend.
Machine sanders are useful for smoothing stock
and for putting draft on the sides of patterns. Be
careful when operating a machine sander so you will
not cut off too much stock and ruin your work.
In this chapter, you have learned about the
different types of wood, wood joints, cuts, and
fasteners that HTs use in their jobs. But remember
when tasked with a job, no matter how small, you
should take the time to pick the right material for
the job. A little extra time taken before you begin
may save a lot of time later.
Figure 3-56.—Sanding at an angle.
Upon completion of this chapter; you will be able to do the following:
Describe the techniques and materials used to repair small craft.
Describe the applications of plastic boats and the procedures used to construct and repair plastic boats.
Recognize the fundamental principles of metal boat repairs and discuss the
safety equipment and procedures used.
Describe the preliminary preparations to be made before laying deck coverings.
Describe the application and installation procedures of tiles and nonskid
boats carried aboard ship. Since inflatable boats are
covered in Basic Military Requirements, NAVEDTRA 12043, they will not be discussed in this text.
As a Hull Maintenance Technician aboard ship
and IMAs, you must be familiar with the procedures
used in making repairs to small boats, because you will
be called upon to make emergency and permanent
repairs on wooden, metal, and plastic boats. Each boat
repair job presents a unique problem, depending on
the type of boat and the nature of the damage to be
repaired. In doing any repair work, the goal is to make
the boat as strong and seaworthy as possible. You may
also be required to repair or even replace deck
coverings. We will discuss the repairs of deck
coverings later in this chapter. Right now, let us look
at boat repairs. The material in this chapter consists
chiefly of examples of small boat repairs and cannot
be taken as step-by-step directions for repairing all
types of damage to all boats.
You will be able to make repairs more intelligently
if you understand the general principles of boat
construction. This information will help you learn the
names of the parts of boats, boat fastenings, and other
terms used by boat builders.
When the construction of a boat is authorized by
NAVSEA, the boat is assigned a BOAT NUMBER.
You will usually find the number cut on the inboard
face of the keel, apron, or keelson.
The label plate is usually secured in a conspicuous
location near the steering control station. This label
contains the following information:
Boat repairs vary and may include repairing
structural members, removing and replacing damaged
planking, caulking seams, making soft patches, and
making plastic repairs.
Length and type of boat
Boat registry number
Maximum capacity (number of personnel)
The types of boats in current use by the Navy
include fast patrol boats used for inshore and riverine
warfare, landing craft carried for amphibious use,
motor whaleboats, utility boats, and motor boats.
Figures 4-1, 4-2, 4-3, 4-4, and 4-5 show some of the
Builder (usually a boat building contractor)
NAVSEA plan number (used for construction)
Date completed
Figure 4-1.—A 26-foot Mk 10 motor whaleboat.
Figure 4-3.—A flag officer’s barge.
slight amount of surface damage may be deceptive and
may cause you to overlook deeper and more serious
damage. For example, a direct blow that is heavy
enough to damage the stem of a utility boat may cause
severe damage to the stem apron, knee, keel, or
keelson; a blow that ruptures the transom planking
may break or crack a stern frame; and a broadside
bump that seems to do little damage might actually
loosen or damage an engine stringer or girder.
To determine the extent of the damage, you will
probably have to scrape the paint away from a fairly
large area. If the stem is damaged, you should remove
the towing post and chafing plate. The towing post
may be removed by pulling the retaining pin, which is
located under the towing post partner, and lifting the
post straight upward from the step or securing plate on
the keel. Figure 4-6 shows a boat from which the
towing post, or bitt, has been removed. On some craft,
it may also be necessary to remove some of the
decking to reach the stem and apron.
Figure 4-2.—Utility boat being used as a personnel carrier.
The first step in repairing a boat is to make a
thorough inspection to determine the extent of the
damage. It is particularly Important to determine the
condition of the main strength members. A relatively
Figure 4-4.—A 36-foot Mk 11 LCPL.
Figure 4-5.—LCVPs hitting the beach.
Almost all of the operational Navy small craft are
now built of glass-reinforced plastic. The wooden
boats that you may have occasion to repair will be odd
types, kept for recreational or historic purposes. The
information in this section will help you make
temporary repairs to these wooden boats. They may
then be operated until permanent repairs can be
performed by technicians assigned to ships or shore
commands with the necessary facilities and skilled
Figure 4-6.—Looking forward on a boat with the towing post
other forms of damage are the result of fire or physical
forces such as collision, grounding, broaching, or other
evidences of poor seamanship.
There is little a Hull Maintenance Technician can
do to prevent physical damage to a boat.
There are three causes of damage to wooden boats.
The most difficult damage to repair is caused by rot. The
by probing with the point of a knife, chisel, or
screwdriver. Press the tip of the instrument against the
wood. If the wood is sound, the point will encounter
increasing resistance as it penetrates deeper. In rotten
wood, the resistance will seem to decrease once the
paint layer is penetrated. A screwdriver tip will seem
to pop through the paint and into rotten wood.
Preventing rot or decay requires joint efforts with
the Boatswain’s Mates or other personnel who are
charged with painting and caulking the boat. You
should inspect boats in your charge fairly often to
check the following causes of decay:
Decay may also be found in association with
physical damage. Weak planks and timber will be the
first to yield to stress. When inspecting collision or
similar damage, look also for signs of rot.
— Parts of the boat may be too dry or too wet.
Strong sunlight or storage near hot machinery can dry
out the wood. Dryness causes wood to shrink and crack.
Water can then seep between planks and into cracks,
wetting interior areas which will not dry before rotting
has started. The microorganisms that cause wood to rot
require a limited range of dampness to be active. Most
of these organisms are fungi, and they will develop in
wood having over 30 percent moisture content. They
need some air, and they will not develop in wood fully
saturated with water, from which comes the term dry
rot. Once in wood, they will be dormant if the moisture
content is less than 20 percent, or if the wood is saturated. Fresh water causes more decay than salt water, so
inspect areas where rainwater or condensation may be
trapped. Boats with closed spaces should have adequate
ventilators installed or hatches opened up and interiors
dried out whenever the weather permits.
Emergency repairs to boat planking can be made
with sheet lead, plywood, canvas, or glass-reinforced
plastic. If the patch is anchored to sound wood, it can
last several weeks. If an emergency patch just covers
a hole and is fastened to rot-affected wood, it should
be replaced as soon as possible.
Most emergency repairs to frame members consist
of reinforcing damaged timbers by backing them up
and shoring them. Backup bracing can be temporarily
nailed or lashed in place. Boats having serious
structural damage are not seaworthy, and temporary
repairs are made only to get them to a safe place where
they can be repaired or surveyed.
— Cracks and seams are places where decay can
start. Not only can dampness persist in narrow cracks,
but other agents that cause decay can get in there. Look
for cracks in boards and faulty caulking. If you find any,
notify the boatswain’s personnel to correct the problem.
The first step in repairing a damaged boat is to
make a general survey of the situation. Determine as
best you can the extent of the damage. Having done
this, consider whether you have the facilities and
materials to make a repair. If work and storage space
are limited, you might have to defer work on the boat
until materials can be obtained. If you have adequate
space, it would be best to haul out the boat for a
detailed inspection and drying out before work is
begun. If the boat has been sunk, the Enginemen will
want to take out the engine, transmission, and
electrical equipment for drying out and overhauling.
If the hull is not repairable, remove the reusable parts
and dispose of the hull.
— Plain iron fasteners or galvanized fittings that
have lost their zinc coating will favor decay in oak frame
members. Also, water may leak into the hull in the
vicinity of these fasteners.
— Caustic chemicals, such as those used in cleaning, should not be allowed to stand in contact with
wood. They can dissolve the wood and weaken it. Acids
are less destructive; but strong acids, such as those used
in batteries, will attack wood.
— A common cause of decay is destructive attacks
by marine borers. This and general marine fouling are
prevented by proper bottom paints and occasional overhaul. Borers are not a problem for boats kept out of the
As soon as a boat has been hauled out, its bottom
should be cleaned. Barnacles and other marine growth
are more easily removed when they are wet. They
smell better then too. After the bottom is cleaned, the
boat can be set up in the work area. The hull should be
dried out, the bilges cleaned, and any rotten wood cut
out so adjacent areas can dry out. When the boat has
Decay, particularly rot, will not start in any place
where it is easy to detect. It may cause cracks and
discoloration of paint, but since it is most likely to
occur in bilges, behind ribs or frames, or in closed
comers, it will be hard to see. Traditionally, it is found
been cleaned and dried, you should make a careful
inspection to determine the extent of damage.
necessary. All frame member sections should be
joined with a scarfjoint if at all possible. A scarf with
a 12:1 pitch is best. A scarf with this pitch, glued with
epoxy and secured by boat nails, bolts, or rivets, will
be nearly as strong as the original member. If you use
epoxy glue, you can allow some gap in the joint since
epoxy has better strength in tension than regular
marine glues. A good scarf can be made by
overlapping the members to be joined and shaping
both ends with one cut of a saw at a steep angle. Heavy
timbers must be sawed and carefully planed to shape.
When a rib or strake cannot be easily reached, the scarf
angle will probably have to be chiseled into it. The end
of the new section then is carefully fitted to this angle.
Since epoxy has strength in tension, rougher faces of
joints can be used than was possible with older glues.
Physical damage may extend far from the
obviously stove-in areas. A boat may have been
squeezed in a collision situation, and although there is
obvious damage on one side, equal stresses have been
suffered on the other side. By calculating the direction
that forces were exerted on the hull, you can estimate
the points where stresses were transmitted. Look in
those areas for loosened fastenings or cracks in the
If decay is present, either as the cause of failure or
incidental to it, you must plan to remove not only the
rotted wood, but also the wood into which the decay
organisms are assumed to have spread. The rule in
doing this is to remove sound wood for 2 feet along
the grain from the soft wood and for 2 inches across
the grain from the soft wood. Plywood should be
removed for a 2-foot radius from the rotten area. If this
is not done, decay can spread back into the repaired
The easiest way to lay out a replacement part is to
use the old part as a template. If the old part is too
badly damaged, you may be able to construct a
template of scrap materials or lay out the new part by
careful measurements. Experienced boatwrights have
a number of techniques to form duplicate replacement
parts, but for emergency repairs you can probably
settle for any method that will fill the hole or provide
adequate reinforcement. Plastic patch materials
permit simple, quick repairs that formerly were not
When you remove a damaged plank, plan to take
out a generous length. The new plank should butt to
the end of the old one between frames, using a butt
block; you should saw the ends to meet that
requirement. If the plank is fastened with screws,
chisel away the putty or the bung plugs and remove
the screws. If boat nails are used, cut off the heads with
a cold chisel. When the plank is pulled off, either pull
the nail or drive it into the frame. To remove rivets,
cut off the upset head and punch them out. (Rivets are
usually found in lap stroke hulls, which are best sent
to an expert for repair.) If the plank is fastened with
drifts, pry them out by leverage on the plank, or allow
the plank to break at the rib, then pull the drift or drive
it flush.
Ferrocement is a material finding increased use as
a low-cost material for hull construction. It is a
combination of steel-reinforced mesh and portland
cement binding. The reinforcement material ranges
from several layers of chicken wire to a few layers of
specially woven steel wire. Ferrocement hulls may
also have some structural steel or steel pipe
reinforcement or framing.
To repair a sprung frame or rib where the exterior
planking is sound, construct a sister frame and fasten
it along the old frame. The sister frame should extend
well to either side of the damaged area. Planks may be
refastened to the sister frame.
Repairable damage to ferrocement hulls probably
will be in the form of punctures or structural damage
from collisions or groundings. Other failure of these
hulls will be caused by poor design, materials, or
workmanship. Hull failure from these causes is not
economically repairable since the seaworthiness of the
entire craft is questionable.
If a frame has rotted, or is badly damaged, it must
be replaced. To replace a curved frame section, it is
easiest and best to laminate the replacement part on a
template; or, if the exterior of the boat is sound, the
section could be built up in place. On Vee hulls, the
lower ribs should go from keel to chine, and the side
ribs from the chine to the sheer strake. The ends should
be joined as were the original members. Curved rib
sections can be joined to the ends of the old rib if
To repair punctured areas not over about 1 foot in
greatest diameter, use the plastic patching kit and
basically the same techniques described later in this
chapter for repairing fiberglass hulls.
resin can be made to cure in periods ranging from 30
minutes to over 24 hours.
Damaged ferrocement can be cut away with a masonry blade in a portable circular saw. The edges of the
hole can then be scarfed with a heavy duty sander, but
not to the degree of taper possible with fiberglass.
Additional reinforcement can be added to the rear of the
patch. Epoxies bond very well to ferrocement.
Larger damage may require some structural reinforcement. Structural steel members may be repaired by
welding, and steel backing to repaired areas can be
welded to structural members. Welding heat will decompose some of the surrounding cement, which
should be chipped away and replaced with epoxy.
To bolt repair patches to ferrocement, use plain
black iron carriage and stove bolts. Galvanized hardware does not stand up well in ferrocement.
Although the use of plastics in naval construction
and repair is relatively new, plastic materials and boats
have become important for naval use.
The factors in favor of the plastic boat are many; it
has a monolithic structure (can be cast in one piece), it
can be mass produced, and it can readily be maintained
and repaired. Ships are supplied with metallic pipe and
general-purpose repair kits. These pipes and kits are
used for emergency repairs of battle damage to piping
for water, oil, gasoline, and refrigeration lines. Materials and instruction are provided not only for repairing
pipes, but also for repairing damaged glass-reinforced
plastic structures such as boats, floats, deck cabins, and
hull and deck coverings.
Some types of damage to plastic boats require slight
deviations from the standard repair procedures, but
personnel who can effectively repair a hole in the hull
should have little or no trouble with other plastic repairs.
Repair Kits
The metallic pipe and general-purpose repair kit are
repair locker equipage. The repair kits are not to be
removed from the repair lockers except in the case of
an emergency and with the authorization from the leading HT or the damage control assistant (DCA), or when
the shelf life date has expired and a new kit has been
placed in the locker. The shelf life of a kit is 2 years.
When a kit is removed from the locker because it is past
its shelf life, the HT shop may keep the kit for boat
repairs and training purposes. The repair kit contains
epoxy resin, hardener, and glass reinforcement in the
form of mats or woven cloth. Auxiliary materials include separating film, kraft paper, protective gloves,
wooden spatulas, resin spreading tools, brushes, and
repair instructions. Sufficient quantities of these materials are provided in a standard kit to replace about 400
square inches of damaged 1/4-inch laminate, and tubes
of paste resin are provided for repairing minor surface
The kit supplier has preweighed and packaged the
resin and hardener in the proper proportions. The resin
cans are only slack filled to allow the hardener to be
added to the can of resin when the two are mixed.
Proper storage of plastic repair kits is important.
They should be stored in a cool, dry place. Temperatures
should be kept below 70°F and the relative humidity
should be less than 50 percent. Kits should never be
stored in temperatures below 32°F. Storage life of the
resin will vary; however, under these specified storage
conditions, the resin should remain stable and usable for
an indefinite period of time.
Plastics in naval construction have become increasingly important. Plastic patching has become standard
practice aboard most ships in the Navy.
Plastics can be identified by their chemical and
physical properties. For repair purposes, the most important plastic categories are the cellulose products, the
protein plastics, and the synthetic resins. Physically,
plastics may be divided into two basic groups: THERMOSETTING materials and THERMOPLASTIC materials. A thermosetting plastic has no melting point.
Although a thermosetting material can flow and be
molded, it will neither soften when heated nor return to
its original liquid state. A thermoplastic material, however, will soften when heated. To illustrate, let us compare these two kinds of plastics with steel and concrete.
Steel can be heated and formed, and when reheated, will
soften; a thermoplastic material is like that. On the other
hand, once concrete has set, it cannot be reformed; this
is characteristic of a thermosetting plastic.
Polyester thermosetting resins, known as polyesters, are extensively used by the Navy. By adding various activators (catalysts and accelerators) in small
quantities to the liquid polyesters, chemical reactions
occur that cause the material to become rigid. This
process of changing from one state to another is called
curing. By varying the percentage of catalyst added, the
closely woven one. Woven fabrics are usually identified
by a style number that refers to a specific cloth or a
certain weave, weight, and thickness. For example,
style #1000 cloth identifies a plain weave cloth that
weighs 10 ounces per square yard and is 0.013-inch
thick. Woven fabrics are coated with a finish to improve
the bond between the glass and the resin. The third type
of glass reinforcement, which is gaining popularity
because it is cheaper than cloth and builds up the thickness of a laminate faster, is called woven roving. This
type of reinforcement resembles a hand-woven potholder both in weave and appearance. A commonly
used type of roving is about 0.040-inch thick and weighs
24 ounces per square yard. Of the three types of reinforcements, the woven fabric is the easiest to handle and
the most dependable for repair work.
Any chemicals or solvents should be handled with
caution. The repair of reinforced plastics is no exception. Cutting and grinding of reinforced plastic laminates generates a fine dust that irritates the skin and
eyes. Inhalation of the dust should be avoided.
The following safety precautions should be followed:
1. Wear protective gloves, goggles, and respirators
provided with the kit. If available, apply a protective
hand cream to all exposed skin areas.
2. Avoid contact with the eyes, skin, or clothing. If
these materials contact the skin or eyes, immediately
flush them with water for 15 minutes. If the eyes are
involved, obtain medical attention.
3. When working in confined spaces, be sure there
is adequate ventilation. Where such ventilation cannot
be provided, organic respirators are required for
protection against fumes.
4. If clothing becomes contaminated, remove it
and wash it thoroughly before reuse.
5. Always wash exposed skin areas thoroughly
when you are finished working.
6. Keep chemical containers clearly labeled and
tightly covered when they are not in use. When mixing
a polyester resin, NEVER mix the catalyst and
accelerator directly together or an explosion may result.
Always mix chemicals according to instructions.
7. Do not smoke or work near hot surfaces or open
flames while using these materials.
Two types of resins are usually used for repairing
reinforced plastics. The first is a polyester, which may
be obtained in a wide range of viscosities. The consistency of the very high-viscosity resin resembles heavy
molasses, while that of the low-viscosity resin is like
water. Usually, the low-viscosity resin will saturate or
“wet-out” a glass reinforcement faster, but it will also
drain more rapidly on a vertical surface. This drainage
may be undesirable in some applications and may be
minimized by the addition of a small amount of a finely
divided silica. A highly viscous resin may be thinned
by the use of a small amount of styrene. Many resins are
available commercially that have been specially compounded to the proper viscosity for repair use.
Polyesters are also extremely versatile in cure
(hardening) characteristics. The addition of a small
amount of an organic peroxide catalyst in a powder,
paste, or liquid form, and an accelerator will cause a
cure to occur at ambient temperatures above 50°F without the application of heat. The working life (time
within which the resin remains liquid and usable) and
cure time may be varied by adjusting the proportions of
the catalyst and accelerator used. The resin supplier will
generally provide information on resin formulations.
Some resins are supplied with the accelerator already
added, thus only the addition of the catalyst is required.
Temperature greatly affects the cure time of polyesters;
the higher the temperature, the faster they will cure.
Polyesters also have a limited storage life of about 6
months to a year. Standing in storage causes them to
gradually thicken until they become unusable even
though the catalyst has not been added.
Basic Considerations
Many factors determine how closely the strength of
a reinforced plastic repair will resemble the strength of
the original laminate. Workmanship, repair techniques,
the glass reinforcement, and resin all play an important
part in any repair. Reinforced plastics are easy to repair
if you have a knowledge of materials used and proper
repair techniques.
Three types of reinforcement are most frequently
used—singly or in combination—in glass-reinforced
plastic laminates. The cheapest and weaker type, random glass mat, consists of chopped glass fibers that are
either lightly bonded together with a small amount of
binder resin, or mechanically stitched into a random,
jackstraw arrangement. These mats may be obtained in
weights from 1/2 ounce to 3 ounces per square foot. The
strongest and most expensive type is woven glass cloth.
It is available in a wide range of weaves and styles,
varying from a coarse, loosely woven fabric to a fine,
Epoxy, the second type of resin that may be used
in reinforced plastics repair at room temperature, is
widely recognized as an adhesive for a great variety
changing hardeners or by cooling or heating the resin.
There are many types of room temperature hardeners
from which to choose. Users are cautioned that room
temperature hardeners are alkaline in nature, so they
should be handled with care. Rubber gloves and eye
protection are recommended when you are handling
epoxy resin and hardener. Always wash the skin
immediately after any contact with the hardener.
of materials. Although better adhesive properties are
generally claimed for epoxies, especially when heat is
applied to achieve a higher strength bond, they are
more costly than polyesters. Like the polyesters,
epoxies are available in a variety of viscosities and
with a wide range of other characteristics.
Epoxy resins are activated for room temperature
cures by the addition of a recommended amount of a
specific room temperature hardener. However, unlike
the polyesters, the proportions of hardener should not
be varied to change the cure time, since any change in
concentration will adversely affect the other
properties. Cure conditions can be varied only by
Repair Procedures
The three types of repair patches applied to
reinforced plastic laminate are shown in figure 4-7.
Figure 4-7.—Types of patches applied to reinforced plastic boats.
They are the surface patch, the one-sided patch, and
the two-sided patch.
Protective equipment, such as goggles and
The basic steps are (1) planning the repair, (2)
preparing the damaged area, (3) tailoring the
reinforcement material, (4) preparing the resin system,
(5) impregnating the reinforcement with resin, (6)
applying the patch, (7) curing (hardening) the patch,
and (8) finishing.
Saw (metal-cutting handsaw, holesaw, or reciprocating saw) for cutting away the damaged area
Disk sander, cone sander, or file for grinding
away the damaged portion and scarfing (beveling edge of cutout area)
PLANNING THE REPAIR.—Before beginning
the repair, several details should be checked and
advance plans made to avoid later problems. If the
repair is to be accomplished in an unsheltered area,
check the weather. If it is cold (below 50°F), rainy, or
blustery, wait for a better day or move to some indoors
area away from the elements. If it is a bright, sunny
day, be sure that the area is well shaded.
Cardboard, sheet metal, or plywood panel for
use as backing and cover plates
Tape, shoring, or bracing for attaching or supporting the backing and cover plates
Acetone for cleaning the surface and the
Assemble the necessary equipment, in the
quantities required, at the repair site. This includes the
materials provided in the plastic repair kit plus the
following supplementary items:
In determining the quantities of materials
required for the repair, outline the area to be cut away
and mark the area to be scarfed (beveled) with chalk
(fig. 4-8). The recommended width of the scarf for
Chalk for marking the area to be repaired
Figure 4-8.—Oval-shaped chalk marks delineate the area to be cut away (inside chalk marks) and the area to be scarfed (outside
chalk mark to inside).
Turn to the nomogram (fig. 4-9) to obtain an estimate of the materials required. Draw a straight line
between scale A (average diameter and/or average area)
on the left side and scale B (thickness) on the right side.
Where this line intersects scale C, read the approximate
amounts of cloth and resin required. Note that the
estimate exceeds the actual requirement by 30 to 40
percent, particularly with respect to cloth, to allow for
wastage. Select from the kit the number and size of cans
of resins and hardener required. To avoid waste, open
and mix the cans as they are needed.
laminates up to three-fourths of an inch thick can be
obtained from figure 4-9.
Round or oval-shaped repairs are preferable to
ensure that you get a better bond and less chance of
cracks in the base material. You should never use
rectangular cuts with sharp comers. To estimate the
amount of resin and glass reinforcement required for
a round patch, determine the thickness of the laminate
and the average diameter. For a rectangular or oval
patch (fig. 4-10), the average area must be estimated.
Figure 4-9.—Estimating materials.
Scale B also indicates the recommended width of
the scarf and the approximate number of plies of cloth
required for any given thickness. The number of plies
required is affected by the variation in the thickness of
the cloth, the viscosity of the resin used (the thicker the
resin, the fewer the plies), and workmanship. The
amount of cloth specified on scale C is based on the
maximum number of plies that might be used, and the
resin estimate is based upon an approximate resin content of 60 percent.
To illustrate the use of the nomogram, assume that
a repair is to be made to an 8-inch diameter hole in a
1/4-inch thick laminate. Looking at scale B, the recommended width of the scarf is 4 inches, and the approximate number of plies of style #1000 glass cloth is 13 to
16. The average diameter will be 8 inches + 4 inches
(fig. 4-9) = 12 inches. Drawing a line between 12 inches
on scale A and 1/4 inch on scale B (see dotted line in
fig. 4-9), approximately 18 square feet of style #1000
glass cloth and 1 quart of resin are required. (As mentioned previously, the materials estimate may be 30 to
40 percent in excess of the actual requirement.)
next step is to prepare the damaged area. This is
accomplished in one of two ways. If the damage
extends only partially through the laminate, merely
grind the damaged area down to the sound laminate
with a disk or cone sander using a coarse abrasive. If
the break is all the way through the laminate, however,
the damaged area should be cut out on the first chalk
mark nearest the damage with a metal cutting handsaw
or reciprocating sabre saw (fig. 4-11). Then, scarf back
Figure 4-10.—Average diameter and area of a patch.
Figure 4-11.—Damaged area being cut away.
When accomplishing a repair on a vertical surface,
use a plate on each side of the patch to hold the patch
in place while it is curing. Cover these plates with
separating film so that they may be removed easily
later. Hold the plates in place by taping, shoring, or
bracing them with lumber (fig. 4-13).
to the second chalk mark (fig. 4-12). This increases
the area to which the patch will adhere so that a
stronger bond may be obtained. The roughened
surface caused by the coarse abrasive provides a better
bond between the old surface and the patch. After the
grinding has been completed, wipe away all the
sanding dust and clean the entire adjacent area with
acetone or lacquer thinner.
If the underside of the damaged area is
inaccessible, apply a resin-wetted backup patch about
2 inches larger than the hole into the scarfed area on
the exposed side. This patch should be allowed to cure
(harden) to form a foundation for the patching
material. After the backup patch has hardened, lightly
sand the surface to provide a better bond between it
and the material to be added later.
The procedure just described is for preparing a
damaged area for the application of a patch on one
side. The patch will generally be placed on the readily
accessible external surface, because it provides greater
resistance to external stresses. However, in instances
where maximum strength is necessary in both
directions, and both sides are readily accessible, it may
be desirable to make a patch on both sides (view C of
fig. 4-7). Both sides are prepared in the same manner
as a repair to one side. Then, the patch must be made
on both sides. Repairs of this type are especially
desirable for thick laminates (three-eighths of an inch
and over). Apply the temporary backing plate to
support the patch while it is curing (hardening). For
small repairs on flat surfaces, the backing plate can be
a piece of heavy cardboard, plywood, or sheet metal.
For curved areas, a formed piece of aluminum or steel
sheet metal is generally preferred.
MATERIAL.—To cut the glass reinforcement to fit
the repair, prepare paper templates for the innermost
ply that are slightly larger than the hole, and for the
outermost ply to barely overlap the scarfed area. Each
of the intermediate plies should be cut proportionally
larger than the preceding smaller ply. (See fig. 4-9 for
the approximate number of plies required for a given
thickness.) If the patch is being made from both sides,
two sets of plies should be tailored as described, one
for each side.
Figure 4-12.—Scarfing operation.
Figure 4-13.—Placing shoring over a film-covered backing plate.
Keep all glass reinforcements clean and dry. They
should not be handled with dirty or greasy hands. Cut
and handle the reinforcement carefully since the cut
edges of some reinforcements unravel easily if
handled carelessly. Glass cloth should be used for
most general repairs, especially where strength is
important. The glass mat may be used in fillets or for
thicker buildups. alone or in combination with glass
in the kit has a relatively short working life that
depends primarily on temperature conditions.
APPLYING THE PATCH.—There are two methods
for preparing the reinforcement material with resin for
applying the patch: method one, which is particularly
desirable for use with the vertical patch; and method
two, which is desirable for use on horizontal surfaces
where impregnated plies can be laid in place one at a
time. In both methods, the first step is to brush a coat
of mixed resin formulation over the area to be
resin and hardener in the repair kit has been
preweighed and packaged in the proper proportions
for mixing. If the temperature is much above 70°F,
bring the resin temperature down to about 70°F, as
higher temperatures will shorten the working life of
the resin. Conversely, if the temperature is low, it is
advisable to keep the resin indoors until used. Prior to
opening the containers, clean and dry them thoroughly
so that no moisture or foreign matter will get into
them. NEVER mix the hardener with the resin until
the preceding steps have been accomplished. The
amount of resin needed for the patch may be estimated
from figure 4-9.
Method One.—On a flat surface lay a piece of
separating film larger than the largest tailored ply of
reinforcement. Center the largest ply of glass cloth on
the separating film and saturate it with resin mix by
brushing or by pouring and spreading the mix with a
wooden spatula from the repair kit. Center the second
tailored ply over the first ply, then impregnate it with
resin. Continue this procedure, saturating each
successive smaller ply thoroughly, until all tailored
plies of reinforcement are finished, with the smallest
ply on top. Apportion the resin so that there is enough
to uniformly saturate all plies. Then cover the
saturated reinforcement with another sheet of
separating film and work the air bubbles out by
squeezing the wet reinforcement from the center
outward with a clean spatula or spreader from the kit.
Keep a close check that the time does not exceed the
Be sure to mix the entire contents of the hardener
container thoroughly with the resin. Once the resin
formulation has been thoroughly mixed, the “die is
cast.” Work ahead steadily to complete the repair
within the working life of the resin. The resin system
working life of the resin. After most of the air and
excess resin have been removed, it may be desirable
to apply another coat of the remaining resin to the
repair area to assure that there is sufficient bonding
squeeze through the next ply, pushing out the
entrapped air. Place a clean sheet of separating film
over the top ply and work out the excess air and resin
from the center to the edge of the patch. A cover plate
may be used.
Next, carefully feed the top layer of separating
film adjacent to the smallest ply from the patch; then
lift and center the patch over the hole with the
separating film on the outside (fig. 4-14). This film
should not be removed. With this film in place, once
again work out any entrapped air and excess resin
using a roller or wooden spatula. This also causes the
patch to make intimate contact with the scarfed area.
When the patch is being made on a vertical surface,
apply a cover plate by taping, clamping, or bracing, to
hold the patch firmly in place during the time needed
for hardening or curing.
If the patch is being applied to both sides, follow
the method being used for each side separately. The
length of scarf and the amount of materials estimated
for the repair on each side should be based on one-half
of the total thickness of the laminate. Apply the patch
to one side; then after it has cured, lightly sand the
opposite side and apply the second patch to that side.
In some applications, a patch can be applied to both
sides in succession (before the first patch cures); however, this procedure requires care and skill.
CURING.—The patch should remain undisturbed at least overnight. Heat lamps may be used
to speed the cure (fig. 4-15); but in using, you should
not overheat the patched area as the cure reaction may
“run away,” causing frothing, blisters, and porosity.
Lamps should be kept at least 1 1/2 feet away. You
should wait a couple of hours to permit the resin to set
at room temperature and then give it a final “kick” with
Method Two.—When using this procedure, you
will lay individual plies of glass directly in place. One
advantage this method has over method one, is that
plies or reinforcements may be omitted or added in the
event the calculated number of plies does not give the
correct thickness buildup. A very liberal coating of
resin must first be applied to the repair area. Then
place the smallest ply of reinforcement in the hole and
saturate it with resin. Add successively larger plies.
Apply sufficient resin to each ply so that it will
FINISHING. —After 12 to 24 hours, the patch is
ready for finishing. The time required will be less than
Figure 4-14.—Entire patch being put in place.
Figure 4-15.—Heat lamps in position to speed the cure.
this if heat is applied; but, in either case, the patch
should be hard and cool to the touch before
proceeding. Remove the cover plate and the
separating film. If it is necessary to do so, fill in
surface pits with the paste resin mix provided in the
kit. Inspect the repair for soundness by tapping it with
a coin or a metal object. A dull thud will indicate
softness, poor bond (delamination) between plies, or
poor bond to the original material. In the event that the
patch is of poor quality, and the effectiveness of the
patch is in doubt, cut out the section slightly larger
than the original patch and redo the repair. Assuming
the job has been done properly, lightly sand the
surface (fig. 4-16). The finish may be a coat of resin
or paint.
repair kit contains an epoxy-type paste resin system
for making minor repairs to damaged plastic surfaces
such as seams, gouges, pits, or small holes. It can also
be used for filling and smoothing patches made with
Figure 4-16.—Sanding a completed patch.
failure later on. For example, if failure is in the bond,
is it the result of insufficient bond area, peeling action,
or poor bonding technique? Examine the bonded area
to ascertain if a uniform and sufficient amount of
adhesive was applied. Compare the amount of the area
that failed within the laminated part with the area that
failed in adhesion at the laminate surface to see if the
surfaces were improperly prepared. Surfaces should
be carefully sanded and cleaned before bonding. Any
repair should be aimed at preventing future failures.
liquid resin systems and glass reinforcements, and for
repairing minor damage to other materials such as
wood and metals. Clean and abrade around the
damaged area. Then, squeeze out the required length
of paste resin from the tube. Parallel to the resin,
squeeze out an equal length of hardener. This may be
done on a flat surface that is covered with a piece of
separating film. Mix the two materials with the small
mixing stick. The resin is white and the hardener is
black; when properly mixed the blend will have a
uniform gray color. Spread the mixture over the
damaged area with the mixing stick or a putty knife.
Cover the repair with a piece of separating film and,
with a clean mixing stick or spreading tool, smooth the
resin from the center outward to obtain the desired
contour. Finish the patch as previously described.
If a stiffener has broken and must be replaced, the
method of repair will depend on whether it has been
integrally molded as shown in view A of figure 4-17
or bonded in place as shown in views B and C. In the
latter cases, the entire stiffener may be completely
removed by delaminating the bond, and a new
stiffener fabricated by the WET LAYUP technique
shown in view B of figure 4-17, or molded separately
and bonded to the plating. The use of positive
fasteners, at least at the ends and center of the stiffener,
is often desirable where service loads are such that a
possibility of peeling exists.
Bolthole Repair
To repair a slightly elongated or oval bolthole
where the washer or bolthole still bears on the
laminate, slightly abrade the enlarged portion of the
hole with a file or sandpaper. Then fill the area of
clearance around the fastener with the paste resin mix.
In the case of integral stiffeners, the damaged
portion should be cut away to the extent necessary to
assure stiffeners a satisfactory repair, and this area
replaced, taking care that a good bond to the plating
and adjacent members is obtained.
To repair a badly damaged bolthole, perhaps
caused by a bolt pulling through the laminate, remove
the bolts and separate the primary structure from any
secondary member where necessary. Cut away the
damaged surrounding area with a metal-cutting saw as
before. From this point, follow the same plastic boat
repair procedures described earlier in this chapter. Put
extra plies of reinforcement in this area to provide
additional strength. After the repair is completed, drill
new boltholes-this time with proper clearance and
bearing area. To prevent recurrence of such a failure,
replace the bolts and washers with a larger size or a
reinforcing plate.
Repairs to stiffeners may be accomplished with
the materials provided in the repair kit and simple
wooden forms, using the repair techniques previously
described. All surfaces to be bonded must be sanded
and cleaned to assure good adhesion. The cross section
and size of the replacement stiffener should be
increased where necessary to provide additional
bonding area or strength.
Repairing Glass-Reinforced Plastic Coatings
Repairing a Damaged Reinforcing
Member or Stiffener
Damaged portions of glass fiber-reinforced resin
coatings on wooden boats and other structures can be
repaired with the resin and glass reinforcement
supplied in the repair kit. The steps for this repair
procedure are outlined as follows:
The stiffeners used in reinforced plastic structures
may be of various shapes that are either integrally
molded with the plating or secondarily bonded to the
plating. Figure 4-17 shows some typical stiffened
panel constructions. Failure may be the result of poor
bonding (in the case of secondarily bonded stiffeners),
inadequate design, or unusual service loads. It is
necessary that such failures be repaired as soon as
possible to avoid further damage to the structure.
1. Cut away any loose or damaged sections of the
glass-resin coating.
2. Repair or replace any of the wood that has been
damaged. Fill seams and cracks with water-mixed wood
putty or plastic wood. The resin and hardener or epoxy
paste supplied in the kit may be used for filling. DO
NOT use oil-base putty.
When you begin the repair, keep in mind the cause
of the failure and correct any defects to prevent similar
Figure 4-17.—Typical stiffeners.
3. After the putty has hardened, sand the area to be
repaired down to the wood and sand the surface of the
resin-coated glass to produce a 6-inch wide abraded
surface around the void.
sheet of separating film over the glass-resin layup and
work out the entrapped air and excess resin by stroking
from the center outward with the spreading tool. Tape
the film in place.
4. Cut the same number of plies used for the
original coating and tailor these to fit the patch and the
abraded area around it.
8. After the patch has set, remove the separating
film. Sand off any excess resin or irregularities. If the
patch is to be painted, sand the surface lightly before
5. Based on the amount of cloth used for the patch,
estimate the amount of resin needed. Mix the liquid
resin and hardener.
Large Hole Repairs
6. Paint a liberal coat of the resin-hardener mixture
over the abraded wood and over the abraded adjacent
In repairing large holes that completely penetrate
the laminate, mark the damaged area with chalk, as
shown earlier in figure 4-8. Using a reciprocating
sabre saw, cut away the damaged area enclosed by the
chalk mark. (See fig. 4-11.)
7. Place one of the plies of cloth over the painted
area and coat it with additional resin-hardener mixture.
Lay up the remaining plies in the same manner. Place a
Figure 4-l8.—Cutting the patch from preformed laminate.
After the damaged area has been cut away, cut the
patch from a section of preformed laminate of about
the same thickness as the area being repaired. (See fig.
4-18.) Center the preformed laminate over the area
being repaired and mark off the area to which the
scarfing will extend, as shown in figure 4-19. If the
opposite side of the area being repaired is accessible,
make a second chalk mark conforming to the hole size
on the preformed patch, as shown in figure 4-18. This
delineates the extent of the scarfing to be done on the
preformed patch. In case the opposite side is
inaccessible, a template may be required to mark off
this area to which the scarfing must extend on the
patch in order for it to fit. Scarf the area around the
hold so that a gradual taper extends back to the chalk
mark, as shown in figure 4-12. Repeat this procedure
Figure 4-19.—Delineating the area where the scarf will
extend on the area being repaired.
Figure 4-20.—Tailoring reinforcement. Laminate has been scarfed to fit level on the area to be repaired.
with the preformed patch. Check to be sure that the
preformed laminate fits snugly over the hole. It should
if the preformed patch and the damaged area have been
properly scarfed. No backing plate is required when
making this type of repair.
To make the reinforcement material, use the
preformed patch as a pattern as shown in figure 4-20
and cut two or more bonding plies of glass cloth. The
reinforcement material should be cut slightly larger
than the preformed patch.
After the resin and hardener have been mixed, apply
a coating to the scarfed section of the area to be repaired.
(See fig. 4-21.) Then, coat the scarfed side of the patch
piece with the resin mixture, as shown in figure 4-22.
Figure 4-21.—Coating the scarfed side of a damaged boat.
Figure 4-22.—Costing the scarfed side of the laminate patch.
Center a bonding ply over the preformed patch as shown
in figure 4-23, and saturate it with resin. (See fig. 4-24.)
Repeat this procedure with the other bonding plies.
Position this assembly over the hole as shown earlier in
figure 4-14, and cover it with a sheet of separating film.
The patch can be held in place by a cover plate, or by
shoring as shown earlier in figure 4-13 until the patch
hardens or cures. The patch is completed in the same
manner as previously described.
patching by abrading the scarfs around the holes.
Patch one skin and allow it to cure. After this patch
has cured, cut and fit the core section. Secure the core
section with repair resin. Then, repair the second skin.
Where damage is to only one skin and core, cut
out a circle of skin with a sharp-cutting tool such as a
hole saw. Cut the skin away from the core material
with a knife. Damaged honeycomb core can be cut
with sharp shears and pulled out with needle nose
pliers. Other types of core material, such as plastic
foam, can be cut out with a knife. Cut a piece of core
material to fit the section that was cut out. Be careful
to match the pattern, if necessary. Cement the material
in place with repair resin and proceed to repair the
outer skin as described previously.
Repairing Double-Skin Plastic Boats
To repair damage that extends through both skins
and the core section of plastic boats, follow the
procedures described earlier under repair procedures.
Cut out the damaged areas and prepare the skins for
Damage to the skin only can be repaired in the
same way as a conventional repair to reinforced
From a wide range of aluminum alloys available
for many purposes, the Navy selected those most
suitable for salt water use for boat hulls. The hulls of
Navy aluminum boats are usually constructed of either
alloy 5086 or 5456. Both alloys contain magnesium as
the primary alloying ingredient, but differ slightly in
strength. In general, these two alloys are not used in
combination except when emergency repairs are
Figure 4-23.—Centering the first bonding ply.
Figure 4-24.—Saturation of the bonding ply with resin.
Alloy 6061 is a general-purpose structure alloy
using a combination of magnesium and silicon as the
chief alloying ingredients. Its use in the Navy should
be restricted to auxiliary systems, such as piping and
railings, and to nonwelded structures.
to be permitted to come in contact with each other.
Observing these precautions enables routine
maintenance to be kept to aminimum.
Galvanic corrosion caused by a dissimilar metal
contacting aluminum can occur. In marine
applications, aluminum and its alloys are frequently
the anodic metal and could corrode in preference to
most other common contacting metals except zinc and
magnesium. However, for galvanic corrosion to occur,
the following conditions must be satisfied: a cell must
be present consisting of at least two metals having
different solution potentials and in electrical contact
with each other (no matter how indirect), and a
conductive medium (electrolyte) must be present
between the metals.
Two other alloys that may be found in limited
quantities are 5083 and 7039. These are used only for
armor and are supplied especially for that purpose. As
such, they should not be used for other structural areas
of an aluminum boat.
Aluminum alloys are not identifiable by
appearance and, therefore, are usually appropriately
marked with alloy and temper designations. The
temper designation follows the alloy number and
indicates the degree of tempering. Tempering is done
in two ways depending on the alloy: either by strain
hardening or by the heat-treatment process. An alloy
that has been strain hardened has a designator
consisting of the letter H and a number, while an alloy
that has been heat treated has a designator consisting
of the letter T and a number. Thus, a plate labeled
5086-H116 has been strain hardened, while one
marked 6061-T6 has been heat treated. Any alloy will
be one or the other; for example, all tempers of 5086
begin with H. The exception is when aluminum is in
the soft, or annealed, condition—indicated by the
suffix 0. Thus, both 5086-9 and 6061-9 (and others)
are available. The temper of material is of concern to
the repairer, since it is desirable to make replacements
of damaged areas with the same alloy and the proper
Three applications account for most galvanic
corrosion situations: (1) connections of aluminum
deckhouse bulkheads to a steel boundary bar; (2) the
attachment of steel or brass fittings to an aluminum
structure; or (3) dissimilar metal appendages, such as
rudders and propellers, on an aluminum hull.
Cleanliness is always important—dirty, wet bilges
or accumulations of dirt and water anywhere are to be
avoided. A freshwater rinse on a regular basis is
generally sufficient.
Cutting aluminum is more like cutting wood than
steel. An oxyacetylene flame is not used because the
excellent thermal conductivity of aluminum carries
heat away too fast to get a good cut. In repair work, all
cutting should be done mechanically using a circular
saw, saber saw, or (in the shop) bandsaw equipment
with metal-cutting blades. Use of a grease stick or lard
oil will prolong blade life. Plasma arc cutting
equipment is available for high-speed production
work but is not needed for repair work. Shearing or
punching of strained hardened alloys should be
Aluminum is a lightweight material, and it is for
this reason that it is used for boats and craft. It is
strong, weldable, and has excellent general corrosion
resistance when proper marine alloys are employed.
In the past, most interior spaces of naval boats were
left unpainted in aluminum construction. There are,
however, some precautions in the handling of
aluminum that must be observed if the full corrosion
resistance capability of aluminum is to be achieved.
Forming is done cold or hot. Aluminum does not
change color with heat and does not glow red as does
steel. Excessive heating can cause the metal to anneal
to the soft condition or even melt or oxidize without
any warning. Hot forming is done by carefully heating
the metal to no more than 450°F. The temperature can
be estimated by the use of temperature-sensitive
crayons. Each crayon is formulated to melt at a
different temperature; and by observing when the
crayon markings on the metal melt, you can remove
the heat source at the proper time.
As with many materials, although mild acidic
solutions cause slight damage, caustic solutions of any
sort such as sodium hydroxide, sodium carbonate, or
sodium phosphate are particularly to be avoided; they
cause severe etching of the aluminum even to the
extent of resulting in perforation.
The most stringent precautions must be taken in
the case of mercury. The presence of mercury even in
small amounts on aluminum causes severe corrosive
attack, and under no circumstances are the two metals
Formed parts of a boat that have been damaged
must not be re-formed using heat. When possible, it is
suggested that the damaged part be replaced by new
material formed for the job.
Distorted plates, whether caused by damage or the
heat of welding, must not be straightened by flamequenching (torch heating followed by spray cooling).
The method does not work well and can result in overheating or melting as previously described. If the distortion does nothing more harmful than detract from
appearance, it should be left alone. Otherwise, distorted
shapes should be straightened cold, using jacks as necessary, while distortion in plate panels may be relieved
either cold or by making a saw cut in the center of the
panel and rewelding it. When you weld a saw cut, ensure
that the correct alloy is used. Cracking of the weld will
result if the alloy of the filler metal or authorized alternate is not used. The normal shrinkage associated with
aluminum welding will tend to remove the distortion.
The light weight of aluminum will facilitate repair
by making handling easier. In addition, the preparation
of subassemblies or repair sections in the shop is greatly
If welding is impractical or impossible, use bolted
aluminum alloy patches. For this type of repair, the
following is needed: an electric circular saw for cutting
plate to size and for fairing out any jagged edges in the
hull penetration, and a good metal-cutting saw blade.
After the patch plate is cut to size, connect it to the hull
with aluminum or stainless steel bolts or other fasteners.
In an emergency, any type of bolt will do. However, this
must be considered a temporary repair since dissimilar
metals cause galvanic corrosion. For bolting the patch
to the hull, insert a sealing material around the perimeter. If a number of repairs of this type are anticipated,
then it might be wise to provide several rolls of the
sealing tapes used by aluminum small boat manufacturers. Most major tape manufacturers supply these tapes
in various thicknesses and widths. These are the tapes
used on modem day aluminum small boats and they do
a good job, not only in sealing the seam, but also in
keeping the rivets and bolts from leaking. The holes for
the rivets or bolts will, of course, be made by a rotary
If the boat incurs damage in a remote area where
there are no facilities for welding, and aluminum is not
available, temporary repairs can be made with steel
patches. Some type of insulation, such as neoprene,
should be used between the aluminum and steel, if
possible. Large, temporary hull repairs can be made in
this manner. The damaged area can be cropped out. The
steel repair plate, including structural framing members, can be prefabricated by welding, leaving sufficient
lap for mechanical fastenings. The unit can then be
bolted to the aluminum hull with insulation between
them. Splices can be made across the structural members. If tapes or neoprene are not available for insulating
the steel and the aluminum, material such as Butyl
rubber, polysulfide, or any heavy-bodied flexible coating will do. Avoid wicking materials, such as flax or
canvas, and the use of lead-pigmented compounds, such
as red lead. The steel temporary repair should be replaced with the proper aluminum repair as soon as
Permanent repairs of steel boats must be
accomplished by qualified welders and nondestructive
test personnel. Fabrication, welding, and inspections
must be accomplished as required by the BoatAlt or
applicable alteration or repair drawing. NAVSEA
0900-060-4010 and NSTM, chapter 074 (9920),
should be used as guides.
In the following sections, the discussion will deal
primarily with typical repairs made to utility boats.
When a boat is damaged, the HT is responsible for
making the required repairs. As an HT, you must know
the procedures for renewing a stem, stem frame, and
engine foundation in a small boat.
In general, the procedures described for repairing
utility boats are similar to those required for repairing
motor boats, motor whale boats, and ships’ boats for
other types.
Before beginning to work on a boat, you must get
it into a safe position, retain its true form, and prevent
further damage, Figure 4-25 shows a type of boat
chock that you can construct aboard ship. It is simply
a framework made from 4 by 4’s and braced with 2 by
6 lumber. The number of chocks and other bracing
should be determined so that the craft can be held
reasonably rigid to a fixed position.
NOTE: When positioning chocks, ensure that they
bear on the hull at structurally reinforced areas.
Remove damaged parts carefully since you will
probably have to use them as patterns in making the new
Stem Apron
Main Stem Piece
Stem Knee
Fore Foot
Rabbet Line
Beading Line
Filling Block
Floor Frame
False Keel
Stem Band
Figure 4-26.—Nomenclature of the bow structure.
Figure 4-25.—Boat chock for shipboard use.
planks have become loosened from the frames and
rabbet. If the planks do not come loose immediately,
remove putty and caulking cotton from the seams and
tap the planking gently with a rawhide mallet, on the
frame side, to help break the seal.
6. When the seal is broken and the planking comes
free from the frames, run a line around each plank and
fasten it to frame 2. This prevents the planking from
springing out and breaking loose farther aft if it
becomes necessary to remove the screws completely to
pull the stem apron.
7. Pass a line through the uppermost bolthole in the
stem and apron, and secure the line to a thwart. This
precaution is necessary to keep the stem and apron from
falling to the deck when the assembly is freed.
8. Remove the breasthook. Then, the stem
assembly will be completely freed.
9. Clean the stem and remove all putty, white lead,
and any foreign matter from the rabbet so that the stem
will form an accurate pattern piece.
parts. As an example of the procedure for removing
damaged parts, a damaged stem can be removed as
1. Carefully scrape the paint from the stem and
from the planking as far aft as necessary, exposing the
countersunk screw holes or the wood plugs over the
2. Remove the metal stem band, chafing plate, and
bow chocks. Also, remove the platform decking to clear
way for work.
3. Remove the brass bolts that secure the stem to
the stem apron and knee. Work from the stem apron
side, and use a drift pin to drive the bolts out. When the
bolts are out, check them for defects; they may require
rethreading or replacing.
4. Remove the brass screw from the stem where it
joins the knee. Figure 4-26 shows the stem and stem
apron assembly in relation to the keel, keelson, and
5. Remove plugs or putty from the screw holes, in
the hull planking, and back out the screws to about
one-half their length. In backing out the screws, start aft
and work forward; except where hull planking is
damaged, all of the damaged material should be
removed. Do not remove any of the screws completely
until all of them have been partially backed out and the
After the damaged stem has been removed and
cleaned, use it as a pattern in making the template. Lay
the damaged stem on a piece of 1/4-inch plywood and
block it in a near-level position. Then, trace the outline
with a pencil. Be sure to keep the pencil vertical so that
the boundaries of the template will be the same as the
boundaries of the stem. Check the boundaries by using
dividers as a test gauge. Then cut the plywood on the
penciled lines, and smooth the template with a plane.
To lay out the rabbet, set the dividers at the distance
from the back of the damaged stem to the outside of the
rabbet; then put the dividers on the template in the same
relative location, and mark the template. Repeat this
procedure along the entire length of the stem, at approximately l-inch intervals, so that the rabbet line will
be marked all the way along the template.
Next, place the template on the lumber, as shown in
figure 4-27, making sure that the maximum strength is
obtained by avoiding as much cross grain as possible.
Mark off the stem on both sides of the lumber, according
to the template; allow 6 to 8 inches excess length above
the capping.
Remove the template, and cut the new stem. Use a
bandsaw to cut within 1/32 inch of the lines; then finish
by planing to the lines. Lay the template on the piece
again, and drive small nails through the template along
the rabbet lines. Drive the nails entirely through the
template and into the piece so that the rabbet lines will
be marked on the piece by the small nail holes. Then,
remove the template and drive small nails into the holes
in the new piece. Draw pencil lines from nail to nail,
and you will have the rabbet lines marked on the new
stem. Figure 4-28 shows the procedure for transferring
rabbet lines.
Chisel a series of notches on the rabbet lines. Be
careful that you do not remove too much wood;
additional paring may be done when the planks are
being fitted to the stem. In cutting the rabbet, use a
piece of planking as a template. Make the steam apron
by copying the damaged piece. You do not have to
make a template, since you can use a bevel square to
get the bending lines and a rule and compass to
determine the overall size. The bevels are set on the
bandsaw; the cuts are then made; the piece is then
trimmed to the lines on the jointer.
Figure 4-27.—Using the template.
Figure 4-28.—Transfer of rabbet lines.
The new stem and the new stem apron must be
very accurately fitted. It is essential to drill the lowest
bolthole on the stem so that it will match up
EXACTLY with the bolthole in the knee. The best way
to make certain that the lowest bolthole on the stem is
aligned with the bolthole in the knee is to clamp the
stem to the knee (using C-clamps and blocks), and
then drill through the bolthole in the knee. Be careful
that you do not enlarge the bolthole in the knee while
you are drilling through the stem.
After this first bolthole has been drilled in the stem,
insert a bolt of the proper size and type and draw it taut.
Then remove the C-clamps and the blocking. Place
cabinetmakers’ clamps over the stem and the knee, at
each end. Then drill the second bolthole, insert the bolt,
and draw it taut. The completion of the job from this
point is just a matter of fairing in, fitting, white leading,
shaping the stem to correspond to the width of the
forefoot, tapering off to the full width at the top, and
drilling holes for stopwater. Do not try to drill the holes
for stopwaters until after the stem has been set in place.
Any damaged planking should be replaced at least
six frames aft of the stem to ensure a substantial
planking jott. If more than one plank must be replaced,
be sure to stagger the after end joints of adjacent
planks so that they are at least two frames apart. Figure
4-29 illustrates a completed stem repair job. Notice
that the boltholes are ready for plugging, and the two
new planks are ready for caulking.
cap as far aft as necessary to enable you to work on the
sheer clamp and the sheer strake. Then remove the sheer
strake by cutting the proper rivets and driving them
from the frames and the clamp. Because of the twist and
curvature of the damaged piece, you will have to remove the sheer clamp much farther aft than the end of
the split. When you have decided where to cut the
clamp, remove the clamp filling blocks for as many
frames forward and aft as necessary to allow you to cut
the clamp. Then saw through the clamp, and remove the
damaged piece.
Select a new piece of timber for the replacement
piece. Surface the piece to the correct thickness, length,
and width, and lay out the scarf joint. Be sure to make
the scarf joint of the proper proportions; the length
should be at least six times the depth. Cut to the lines,
and smooth the wood with a sharp chisel and a plane.
Make a pattern of the finished scarf, and transfer the
lines to the undamaged section of the clamp. Cut and
smooth the scarf on the undamaged section, as you did
on the new piece.
Steam the new piece and bend it to the proper shape.
Using C-clamps or cabinetmakers’ draw clamps, clamp
the new piece in place from the scarf end forward, and
reinstall the filling blocks. Drill the scarf joint for carriage bolts, insert the bolts, and tighten the nuts over
washers. Figure 4-30 shows the completed scarf on the
sheer clamp.
Figure 4-29.—Completed repair to a stem.
Suppose the sheer clamp is split from the apron to
as far aft as the sixth or seventh frame. How would you
proceed to repair the damage? First, remove the sheer
Figure 4-30.—Completed scarf joint on the shear clams.
the after-deck area of the rudder assembly, taff railing,
and all hardware; and then remove the decking. Figure
4-33 shows the stem with the hardware and the
decking removed, but with deck supports still in place.
Figure 4-34 shows the deck supports and the transom
Loosen the draw clamps and replace the sheer
strake. Then put the clamps on again and draw them
taut. Using the existing rivet holes in the sheer strake
as a guide, drill holes for 1/4-inch copper rivets. Then
rivet the clamp to the breast hook. Nail the sheer strake
in place, using 4-inch copper nails, and trim the upper
edges to conform with the camber. Then install the
capping, and the repair job is finished except for
caulking, sanding, puttying, and painting.
Remove all screws that join the transom planking
to the inner frame, and remove the copper rivets that
fasten the transom planking and the outer bounding
frame to the inner bounding frame. The outer
bounding frame is a filler piece, and will come free
when the seal is broken. The inner frame, which is in
four pieces, should be removed to the joint nearest the
break. The procedure for laying out, cutting,
smoothing, and fitting the replacement pieces is the
same as that previously described for other members.
Let’s assume that you have to renew a transom
bounding frame, the stern-post knee, and deck
supports on a wooden boat. Figure 4-31 shows details
of transom construction. Figure 4-32 shows the outer
bounding frame of the starboard transom, ready for
repair. Note that the transom angles have been
removed, and the paint has been scraped off.
Procedures for renewing engine foundations vary
considerably, depending upon the type of boat. In
To remove the outer bounding frame, you must
also remove the inner frame. To do this, you must strip
Figure 4-31.—Transom construction.
Figure 4-34.—Deck supports and transom knee.
Figure 4-32.—Outer bounding frame, starboard transom.
is usually secured to the engine stringer with bolts.
Engine hold-down bolts are installed with the heads at
the seam between the engine bed and engine stringer.
These bolts protrude upward about 2 or 3 inches above
the top of the engine bed, and the engine is fitted over
the protruding end. A nut is used on each of these bolts
to hold the engine in place. Gaps are cut at the seam
between the engine bed and the engine stringer to
allow access to the heads of the hold-down bolts.
The qualities required in deck coverings for naval
ships include nonflammability, wear resistance,
lightness of weight, slip resistance, ability to protect
steel decks from corrosion, good appearance, and ease
of maintenance. Simplicity of application and the
initial cost of the material are also important
Figure 4-33.—View of stern, with decking removed.
performing this job, remove the engine and the
damaged pieces carefully so that you can use them to
make templates.
As a rule, the engine stringer is secured to the floor
timber with rods. Since the nuts are on the face of the
stringer, you must back off the underneath planking
so that the rods may be removed, when necessary, to
replace the stringers or defective parts. The engine bed
A number of different kinds of deck coverings are
available. However, deck coverings used in any area
aboard ship must be according to NAVSEA
instructions and specifications. Information on deck
coverings that are not discussed in this chapter may be
obtained from NSTM, chapter 634.
In general, an existing deck covering in
satisfactory condition should not be replaced even if
it does not agree with the materials listed for the
specific space. New deck coverings should be
installed only where existing authorized deck
coverings are beyond economical repair. When repairs
are required, they should be performed locally if
possible. When complete removal and reinstallation
of a new deck covering is required, an approved deck
covering for the specific location should be installed.
The tile and the roll decking must meet the fire
requirements of MIL-STD-1623. Rubber tile or roll
deck coverings should be installed one-eighth of an
inch thick, except where durability is required for the
heaviest traffic areas. In this case, the thickness should
be three-sixteenths of an inch. The adhesive used to
cement vinyl asbestos tile may be used for the rubber
decking materials, as well as other
NAVSEA-approved equivalents. Immediately after
the installation of the rubber decking, the deck should
be rolled thoroughly in both directions with a
150-pound sectional roller.
A deck covering should cover the entire deck area
of a compartment unless otherwise specified, except
that it should not be installed under enclosed built-in
furniture nor under equipment with enclosed
All deck covering and adhesives should be stored
for at least 24 hours at a temperature of 70°F or higher
prior to installation. Spaces should be maintained at a
temperature of at least 70°F prior to, during, and 24
hours after the installation is completed. A beading
sealer should be used to waterproof all seams against
bulkheads, stationary furniture, pipes, and other deck
fittings. Where weld lines (beads) prevent the deck
covering from butting tightly against the ship’s
structure, caulking compound should be used to fill
the gap, and painted to blend with the deck tile or
bulkhead after the caulking compound skins over.
Alternatively, weld lines against bulkheads may be
made even by filling underlay material and the tile
butted against the bulkhead. This latter method
produces a better appearance. If desired, the tile may
be squared off where it is in the way of vertical
stiffeners and stanchions.
Before laying any type of deck covering, be sure
that the deck is clean and free of rust, loose scale, and
dirt; grease and oil should be removed with solvents
and clean rags. Paint and primers that adhere strongly
to the deck may be left intact unless otherwise
Certain adhesives and compounds used in the
application of deck coverings contain flammable
solvents. Safety and health measures to be taken
depend upon the flash points and toxicity of the
solvents. Be sure to comply with all applicable safety
Marbleized fire-retardant vinyl tile, one-eighth of
an inch thick, is the standard Navy deck tile approved
for shipboard use. Vinyl tile is stocked in eight
marbleized colors.
Preparation of Steel Decks
Deck tile should be laid over bare wood, plastic,
or cleaned base metal that has been primed with
formula 150 MIL-P-24441. Tile must not be installed
more than two layers thick because the additional
layers increase the fire hazard. In general, when laying
new tile, remove tile down to base metal or wood if
two layers have previously been installed. Prime the
deck to prevent corrosion if it is made of metal.
Steel decks must be clean, free from oil, grease,
rust, and loose scale. It is not necessary to remove red
lead or zinc-chromate priming paint, or deck paint if
they are well bonded to the deck; otherwise, loose
paint, rust, and scale should be removed by blasting,
wire brushing, or any other effective method. The deck
should then be washed with approved solvents to
remove grease and contaminants and the steel primed
with formula 150, 2- to 4-mils dry-film thickness. If
possible, weld seams should be ground flush with the
deck, and all low spots should be filled with underlay,
MIL-D-3135, type II. All high spots should be ground
down, if possible, or faired with underlay before
Fire-retardant deck tile should conform to
MIL-T-18830 or other NAVSEA-approved
equivalent, and they should be installed with a latex
cement, except in damp or wet areas where it is
advisable to use an epoxy adhesive.
applying the primer. The deck must be dry at the time
the deck covering is installed.
Water can affect adhesive and loosen tiles; therefore,
swabbing the deck should not be done for 1 week after
installation; for general cleaning, use water sparingly to
prevent corrosion under tiles.
Application of Deck Tile
Installation pointers for laying rubber and vinyl
tile are as follows:
Installation of Rubber Roll,
Vinyl Sheet, or Mat
1. Store the tiles for 24 hours at a minimum
temperature of 70°F. (At temperatures below 70°F, the
material is not sufficiently flexible for satisfactory
installation.) To ensure straight seams, square off the
areas to be covered and, if practicable, start the
installation of tile at the center of the space and work to
the edges to achieve an even balance of tile around the
edges of the space.
When installing these materials in front of
equipment only, cut the sheet to the desired length and,
with a straightedge, cut off the selvedge (if applicable)
before cementing the sheet. When installing sheeting
material over an entire deck area, lay out the space,
cutting all sheets to the desired length; then overlap
edges of the sheet so all seams can be double cut, using
a straightedge, to assure tight fit. After the material has
been cut and fitted, roll the sheets back and cement
half the space. Lay sheets down into position. Then
repeat the process for the other half.
2. If a pattern of two or more colors is desired, plan
this on graph paper in advance (each square of the paper
can be considered one tile). For spaces with nonparallel
opposite bulkheads, use a large square and chalk line at
comers to square off the compartment into a rectangular
or square layout. To locate the center of the space, strike
a chalk line from the midpoints of opposite bulkheads
after squaring off.
1. When cementing, use a latex-type adhesive
conforming to MIL-A-21016. If a sheet has a tendency
to bubble or lift after installation, it may be necessary
to substitute a stronger adhesive such as an epoxy
adhesive. The adhesive should be spread with a notched
trowel, making certain that the entire surface is covered.
When the adhesive is tacky, install the sheet.
Immediately after installation thoroughly roll the deck
in both directions with a 150-pound sectional roller.
3. It is important that installation start at sections
of the space where work can proceed to completion
without kneeling on freshly laid tile. Cement should be
spread with a fine-toothed trowel (approximately 1
square yard at a time) at a coverage of 100 square feet
per gallon (excess cement will reduce adhesion). While
the cement is tacky, force the tiles into tight contact with
each other. Half tiles can be cut by scoring and cutting
through with a sharp knife. Vinyl asbestos tile should
be made flexible by heating before cutting. A dull or
unpointed linoleum knife should not be used for cutting
the tiles because uneven edges will result.
2. For additional information concerning
materials used to prevent electric shock, see NSTM,
chapter 634.
Repair or Replacement of Deck Tiles
If a tile requires replacement, remove it by forcing
a wide-blade paint scraper under it. Inspect for
corrosion. Chip out the dried cement and corrosion
products to bare steel, clean the spot with paint
thinner, coat it with primer, and apply tile as
previously described.
Care also should be taken that the cement does not
get on the surface of the tiles. Excess cement may be
cleaned off, while wet, with a damp rag. If cement is
dry, a rag that has been wet with paint thinner will
remove the cement. Pressure should be applied to
ensure complete contact of each tile with the deck.
Any high joints remaining after this operation should
be rubbed even and smooth with a hand roller.
Latex underlay should conform to MIL-D-3135,
type I, for use under latex terrazzo, latex, mastic, and
ceramic tile.
4. Travel over the newly cemented areas should be
restricted until the installation is completed; then the
deck can be opened to foot traffic immediately since no
indentations will occur from this type of traffic
However, it is recommended that heavy concentrated
loads, such as legs of heavy furniture, be kept off the
deck until the cement has set (approximately 18 hours).
Surface Preparation
Remove rust and paint. Clean the deck free of oil,
grease, and dirt with an approved degreasing solvent.
Apply one coat of epoxy primer, formula 150,
MIL-P-24441, 2- to 4-mils dry-film thickness,
according to NSTM, chapter 631.
formula 150, MIL-P-24441, 2- to 4-mils dry-film
thickness, or an equivalent coating.
Surface Wetting Coat
One part rubber latex mixed thoroughly with 2
parts underlay powder by weight should be brushed
on in a thin coat, assuring that all of the deck is wetted
thoroughly. The purpose of the wetting coat is to
assure that the underlay bonds securely to the surface.
The on-deck magnesia insulation should be
trowelled smooth, a minimum of 1 inch thick over
rough finish latex underlay MIL-D-3135, type I.
Apply a one-eighth inch minimum thickness of
underlay. Exposed aluminum fittings should be
protected from corrosive attack from the magnesia by
either a coating satisfactory for aluminum (see NSTM,
chapter 631) or a suitable covering such as a wrapping
of a vinyl tape.
Underlay Body Coat
Mix thoroughly 1 part rubber latex, 1 1/2 parts of
underlay powder, and 1 1/2 parts aggregate (all by
weight). Mix only in such quantity that the material
will not set up before application. Make certain there
are no dry particles left. The following approximate
quantities of materials are required to cover 100
square feet (one-fourth of an inch thick):
Rubber terrazzo, which is used in washrooms,
showers, sculleries, and water closets, is a colored
material that contains chips of white and colored
marble. The material is mixed at the time of
application and is applied with trowels; it requires
machine grinding to provide a smooth surface. The
usual thickness of application is one-fourth of an inch.
The material may be applied to a maximum of one-half
of an inch without causing the wet mix to sag. If
greater thickness must be used, apply latex underlay
49 lb rubber latex
73 lb underlay powder
73 lb underlay aggregate
While the surface wetting coat is still wet, trowel
on the underlay body coat and level off with battens.
After leveling off, go over the surface with steel
trowels, working down hard to flow the mix together
and to blend it with the surface wetting coat. Allow
the surface to dry hard (at least 2 days) before applying
the deck covering. If the underlay is used in excess of
one-half inch thick in one layer, it will tend to develop
hairline cracks. Latex underlayment for use under
deck tile and resilient sheeting should conform to
MIL-D-3135, type II, and should be installed
according to the manufacturer’s directions. Type II
can be featheredged and trowelled to a smooth finish
without sanding.
The materials required for mixing rubber terrazzo
are as follows:
Liquid latex
Grout powder
Terrazzo mix (including aggregate)
Before rubber terrazzo is applied, the deck surface
and 4 inches of vertical bounding surfaces against
which the covering will abut must be cleansed by
wirebrushing or similar methods. If necessary, the
deck should be faired with underlay in low spots and
around rivets and welds.
Insulation underlay may be used to prevent
condensation such as occurs on ballast tank tops and
heat from the overheads of machinery spaces,
especially where these surfaces form the decks of
living spaces. The magnesia insulation that is used
should conform to MIL-D-23134.
After the deck has been cleaned, give it a wetting
coat of grout. Mix, apply, seal, and grind the terrazzo
according to the manufacturer’s instructions. Allow
the terrazzo to dry for 72 hours before grinding it.
After grinding, clean the deck with a broom or a
vacuum cleaner. This should produce a smooth,
durable, nonporous surface in which the marble chips
are uniformly distributed and firmly embedded. Cover
Surface Preparation
Remove and clean the deck free of rust, dirt, old
paint, oil, and grease. Apply one coat of epoxy primer,
water, using a damp, clean mop. Rubber heel marks,
grease, and dirt may be removed with a rag moistened
with paint thinner or by using fine steel wool and soap.
After washing and after the deck is completely dry, the
tile may be buffed with a buffing machine or it may
be given a coat of wax and allowed to dry without
polishing. A slip-resistant water emulsion type of
floor wax is available and should be used when
the deck with sealer. Allow the sealer to dry, and then
apply a second coat of sealer to complete the job.
Nonskid deck treads are similar to a coarse emery
cloth. The treads, which are approximately 6 inches
wide and 24 inches long, are installed at the head and
foot of ladders and at each side of doors with high
coarnings that are used for continuous traffic. The
treads are generally placed about 2 inches apart.
If a high gloss is desired, the dried wax may be
buffed with a polishing machine. To conserve wax and
reduce maintenance, a deck should be buffed several
times before it is rewaxed. The deck may only require
rewaxing in the traffic lanes once a week. If dirty spots
are wiped up promptly with a damp rag and the areas
are immediately repolished, a complete refinishing
job may be deferred for a long time.
The treads, which have a pressure-sensitive
adhesive backing, are cut from rolls or ordered in
boxes of 50 each. The comers of the treads should be
rounded before installation. Nonskid deck treads may
be installed over finish paint or primers and over deck
tile, provided the surface is free of grease, oil, floor
wax, and dirt or dust. If nonskid deck treads are
applied to unpainted steel decks, all dirt, rust, and
foreign matter must be removed by wire brushing. The
installation of these treads over a poorly prepared steel
deck can result in severe deterioration of the deck.
Do not apply lacquer, plastic, or other hard
finishes to deck coverings. These finishes tend to
become yellow and to wear off in traffic.
The most painstaking and careful maintenance of
deck coverings may be wasted through careless
treatment. The legs of furniture, especially chairs and
other movable pieces, should be properly fitted with
rubber tips to prevent scratching and denting of the
deck covering. Nonslip rubber tips are available.
Heavy objects should not be dragged across resilient
deck coverings unless they are protected. Also, deck
coverings should be protected with cover cloths and
scrap materials during painting and during shipyard
After the nonskid deck treads are installed, they
should be rolled with a weighted roller. The edges
must then be sealed with an approved beading sealer.
Deck coverings should not be washed more often
than necessary.
When necessary, they should be mopped with a
damp mop, using a synthetic detergent solution. Two
tablespoons of cleaner per gallon of warm potable
water is recommended. Deck coverings should not be
flooded with detergent solution; only a limited
quantity of solution should be used. Using excessive
quantities of water or detergent solution is damaging
to the deck covering and may cause the covering to
come loose from the deck.
With the knowledge gained on emergency repairs
of small boats and the assistance of experienced
personnel, you should be able to keep your craft
operational until permanent repairs can be made. And
if the need arises, the repair or replacement of the
various types of deck coverings may be made,
provided that the proper materials and equipment are
available to complete the job.
Deck coverings should not be cleaned with strong
alkaline soaps, abrasive cleaning powders, or salt
water. All water, cleaning compounds, and dirt should
be removed and the deck rinsed with clean, fresh
Upon completion of this chapter; you will be able to do the following:
Describe the characteristics and use of some special tools used by Hull
Technicians in the performance of their duties.
Point out the features, purpose, and techniques of using calipers, torque
wrenches, gauges, and squares.
Describe the setup, operation, and maintenance of various portable shop
tools and machine power tools, and identify some of the safety precautions
to observe when using them.
Describe the construction and safety devices of compressed gas cylinders and
the safety precautions to observe when handling them.
Identify the color codes, test and repair procedures, and handling and
stowage requirements of compressed gas cylinders.
rather than repeat, the information in Use and Care of
Hand Tools and Measuring Tools, NAVEDTRA
12085, and the manufacturer's operating manual. You
should qualify on each piece of equipment in your
specific work center according to the manufacturer’s
technical manual and any locally written instruction
prior to the setup and operation of any tool or
Tools are designed to make a job easier and enable
you to work more efficiently. Regardless of the type
of work to be done, Hull Maintenance Technicians
must have, choose, and use the correct tools to do their
work quickly, accurately, and safely. Without the
proper tools and the knowledge of how to use them,
they waste time, reduce their efficiency, and may even
injure themselves or cause others to be injured.
As a HT, you will be required to use many
different handtools and instruments. Each tool does a
specific job. To become a skilled craftsman, you
should learn what each tool can do and select the
proper tool for the job. The proper use and care of tools
enable you to turn out quality work and help you
develop safe work habits.
This chapter explains the specific purposes,
correct use, and proper care of some of the specialty
tools you may use, such as portable shop tools,
machine tools, compressed gas cylinders pneumatic
tools, portable power tools, and some installed shop
equipment. The various tools discussed here are by no
means all the tools that exist in this group. They are
the specialty tools you will normally find in an HT
shop. Equipment that is used only for one purpose, or
in connection with one particular skill, is covered in
the appropriate chapter or chapters of this training
manual. It is not the intent of this chapter to introduce
or instruct you on the use of every tool or piece of
equipment you may encounter in the workshop. The
material in this chapter is intended to supplement,
The measuring tools found in a shop include
various types of rules, calipers, squares, and gauges.
They are used to measure lengths, diameters, angles,
and radii. Use and Care of Hand Tools and Measuring Tools, NAVEDTRA 12085, and Machinery
Repairman, NAVEDTRA 12204-A, contain more
Manufacturers’ and technical manuals generally
specify the amount of torque to be applied. To assure
getting the correct amount of torque on the fasteners,
the wrench must be used properly according to manufacturers’ instructions.
Use that torque wrench that will read about midrange for the amount of torque to be applied. BE SURE
the accuracy of torque measuring depends a lot on how
the threads are cut and the cleanliness of the threads.
Make sure you inspect and clean the threads. If the
manufacturer specifies a thread lubricant, it must be
used to obtain the most accurate torque reading. When
using the deflecting-beam or dial-indicating wrenches,
hold the torque at the desired value until the reading is
Torque wrenches are delicate and expensive tools.
The following precautions should be observed when
using them:
information on measuring and marking tools. In this
section we will cover the use of specialty measuring
devices such as torque wrenches, calipers, feeler
gauges, metal gauges, and squares.
There are times when, for engineering reasons, a
definite force must be applied to a nut or bolt head. In
such cases a torque wrench must be used. For example,
equal force must be applied to all the head bolts of an
engine. Otherwise, one bolt may bear the brunt of the
force of internal combustion and ultimately cause engine failure.
The three most commonly used torque wrenches
are the deflecting-beam, dial-indicating, and micrometer-setting types (fig. 5-1). When using the deflecting
beam and the dial-indicating torque wrenches, the
torque is read visually on a dial or scale mounted on the
handle of the wrench.
To use the micrometer-setting torque wrench, unlock the grip and adjust the handle to the desired setting
on the micrometer-type scale, then relock the grip.
Install the required socket or adapter to the square drive
of the handle. Place the wrench assembly on the nut or
bolt and pull in a clockwise direction with a smooth,
steady motion. (A fast or jerky motion will result in an
improperly torqued unit.) When the torque applied
reaches the torque value, which is indicated on the
handle setting, a signal mechanism will automatically
issue an audible click, and the handle will release or
“break,” and move freely for a short distance. The
release and free travel is easily felt, so there is no doubt
about when the torquing process is complete.
When using the micrometer-setting type, do
not move the setting handle below the lowest
torque setting. However, it should be placed
at its lowest setting prior to returning to storage.
Do not use the torque wrench to apply greater
amounts of torque than its rated capacity.
Do not use the torque wrench to break loose
bolts that have been previously tightened.
Do not drop the wrench. If dropped, the accuracy will be affected.
Figure 5-1.—Torque wrenches.
Calipers are precision measuring devices that
measure length in thousandths of an inch. Calipers
differ only in the way they are read and the types of
measurements taken. The types of calipers that will be
discussed in this chapter are the vernier dial caliper
and the vernier.
fixed measuring jaws to measure inside and outside
measurements as shown in figure 5-2. Depth is measured using a depth gauge rod.
Reading the vernier dial caliper is a relatively simple and easy task involving the addition of the dial
reading to the main frame scale reading. It uses a dial
marked in thousandths of an inch and a main frame scale
marked in inches and hundred-thousandths of an inch.
As the dial is drawn across the main frame by an
adjustment screw, the reading is registered on the dial
face in thousandths of an inch. Before taking your
measurement, always zero the dial caliper by aligning
the mark on the bezel when the measuring jaws are
closed. When you pass the first small numbered mark
on the main frame scale, simply add one hundred thousandths to the dial reading. When you pass the first large
numbered mark on the main frame scale, add one inch
to your dial reading. After passing the first small numbered mark, add one inch one hundred thousandths to
the dial reading. Do this wherever the reading falls on
the scale.
Vernier Dial Calipers
Vernier Caliper
Vernier dial calipers are the most common type of
caliper found in use today. They are preferred over
vernier calipers in that they are easier to read and can
measure depth. They use a double set of movable and
Vernier calipers are capable of taking measurements to the nearest thousandths of an inch using a stationary and sliding jaw assembly as shown in figure 5-2.
Reading the vernier caliper is not as easy as reading the
Do not apply a torque wrench to a nut that has
been tightened. Back off the nut one turn with
a nontorque wrench and retighten to the correct torque with the indicating torque wrench.
Calibration intervals have been established
for all torque tools used in the Navy.
When a tool is calibrated by a qualified calibration
activity at a shipyard, tender, or repair ship, a label
showing the next calibration due date is attached to the
handle. This date should be checked before a torque
tool is used to ensure that it is not overdue for
Figure 5-2.—Vernier and vernier dial caliper.
importance. Some of the more important aspects of
caliper maintenance are listed as follows:
dial caliper (refer to fig. 5-3). The main frame scale (1)
is graduated in 0.025 thousandths of an inch. Every
fourth division (2) (representing a tenth of an inch) is
numbered. The vernier scale (3). on the movable jaw, is
divided into 25 parts and numbered 0, 5, 10, 15, 20, and
25. These 25 parts are equal to 24 parts on the main
frame scale (1). The difference between the width of one
of the 25 spaces on the vernier scale (3) and one of the
24 spaces on the main frame scale (1) is 1/1000 of an
There are five steps to reading the vernier caliper
as shown in figure 5-3. They are as follows:
— Always store the caliper in its carrying case.
Never leave calipers on work benches, table tops, weld
booths, machinery or equipment, or other areas where
the caliper could be knocked off, crushed, bent, or
otherwise damaged.
— Calipers should always be calibrated according
to the Navy’s METCAL program before use.
— Keep the slide and main frame clean and free
of dust, dirt, weld splatter, and metal chips.
1. Read the number of whole inches on the top
scale (1) to the left of the vernier zero index (4)
and record as 1.000 inch.
— Never force the slide. If the slide does not move
freely, check for chips or grit on the rack and remove
them by cleaning.
2. Read the number of tenths (5) to the left of the
vernier zero index (4) and record as 0.400 inch.
3. Read the number of twenty-fifths (6) between
the tenths mark (5) and the vernier zero index
(4) and record as 3 × 0.025 or 0.075 inch.
There are numerous gauges in use throughout the
Navy today. As an HT, you will use numerous gauges
to perform your job. This section will discuss various
gauges that are used in drilling, tapping, welding, and
brazing operations.
4. Read the highest line on the vernier scale (3)
which lines up with the lines on the top scale (7)
and record as 11/25 or 0.011 inch. (Remember,
1/25 = 0.001 inch.)
5. Add the total measurement of the 4 preceding
steps to find the total measured length or 1.000
+ 0.400 + 0.075 + 0.011 = 1.486 inches.
Thickness (Feeler) Gauges
Feeler gauges are used for checking and measuring
small openings such as root openings and narrow slots
found in weld fitups and braze joints. Thickness gauges
come in many shapes and sizes, as shown in figure 5-4,
and can be made with multiple blades (usually have 2
to 26). Each blade is a specific number of thousandths
of an inch thick. This enables the application of one tool
to the measurement of a variety of thicknesses. Two or
Vernier calipers only take inside and outside
dimensions and cannot take depth readings.
Caliper Maintenance
Since calipers are precision measuring instruments, proper care of the caliper is of great
Figure 5-3.—Reading a vernier caliper.
Figure 5-4.—Thickness (feeler) gauges.
Figure 5-5.—Screw-pitch gauges.
more blades may be combined to take readings of
various thicknesses.
Screw-Pitch Gauges
Screw-pitch gauges (fig. 5-5) are made for checking
the pitch of U.S. Standard, Metric, National Form, and
V-form cut threads. You will use them to determine the
correct thread pitch of an unknown thread on a bolt,
inside a nut, or in choosing the correct tap or die for
threading stock or tapping a hole. Each thread gauge is
marked in number of threads per inch. To take a measurement, simply lay the gauge on the thread. The correct
gauge will fit the thread of the bolt perfectly with no
light showing between the gauge and the threads of the
bolt. The pitch of the screw thread is the distance
between the center of one tooth to the center of the next
Drill Gauges
The twist drill and drill rod gauge has a series
of holes with size and decimal equivalents stamped
adjacent to each hole, as shown in figure 5-6. Drill
gauges use either a letter, number, decimal, or fraction
Figure 5-6.—Drill gauges.
Figure 5-7.—Steel plate and sheet metal gauges and thicknesses.
to designate drill size. Some drill gauges may use a
combination of these designations to measure drill size.
You will use these gauges when determining the correct
drill size for a given tap size.
directly below that mark to get the total length of plate
needed to manufacture a 2-inch diameter cylinder or
6 1/4 inches. The total length of plate needed is 6 1/4
Steel Plate and Sheet Metal Gauge
Steel plate and sheet metal gauges come in various
sizes and uses, as shown in figure 5-7. You will use them
extensively in sheet metal and structural metal fabrication to determine metal thickness or gauge. They are
simple to use and extremely accurate. Simply fit the
gauge to the plate so that the metal edge slides exactly
into the slot. The gauge should be snug, but do not force
the gauge onto the metal. Gauge numbers are marked
on the front of the gauge with the corresponding decimal reading on the back.
Working in an HT shop, you will use a square
almost everyday. Squares are versatile instruments
that can be used to lay out lines and angles, to measure
distances, and for numerous other functions. There are
numerous squares in use today, but only the steel
square and the combination square will be discussed
in this section.
Steel Square
Steel squares (fig. 5-9) are used to lay out various
angles and to check squareness or straightness of an
edge or surface. They are L-shaped tools that comes in
12-, 18-, and 24-inch blade length. They are marked in
graduations of 1-16- or 1/8-inch divisions on the inside
and outside edge. The components of the steel square
are as follows:
The circumference rule is a specialty rule that is
used to figure out the total length of plate needed for
manufacturing cylindrical objects. The circumference
rule looks similar to a regular steel rule but has two
scales marked on its face as shown in figure 5-8. The
top scale is an inch scale that is divided in sixteenths
of an inch and represents the diameter of an object.
The bottom scale is divided in eighths of an inch and
represents the circumference of a cylinder. The back
of the rule usually has formulas for calculating
circumferences and shows areas and tables for laying
out measurements.
BLADE—the longer leg of the square
TONGUE—the shorter leg of the square
HEEL—the outside comer
FACE—the inside edge of the square
Reading the circumference rule is a simple process
that requires no special math skills. First, determine
the diameter of a cylinder in inches. Next, locate the
diameter on the top inch scale and read the
measurement directly below on the circumference
scale to determine the total length of material needed
to fabricate the cylinder.
BACK—the outside edge of the blade
When using a steel square to lay out angles, place
the tongue of the square on the base line with the
12-inch mark on the vertex of the desired angle. Mark
the vertical distance for the desired angle along the
blade edge of the square. Connect the vertex to the
vertical height mark with a line. Some of the more
common angles are shown in figure 5-10.
Using figure 5-8 as a guide, let’s figure the total
length of plate needed to manufacture a 2-inch
diameter cylinder. Locate the diameter, or 2 inches, on
the top inch scale, then read the circumference rule
Combination Square
The combination square (fig. 5-11) is a
multifunctional tool that can be used to lay out various
angles, measure height and depth, bisect a 90-degree
angle, and as a level. It consists of the following
— A 12-inch stainless steel rule (1) that is graduated in eighths, sixteenths, thirty-seconds, and sixtyfourths of an inch. The rule is slotted to accept
individual tool heads. It can be used as a measuring
Figure 5-8.—Circumference rule.
Figure 5-9.—Steel square.
Figure 5-10.—Steel square angle layout.
Figure 5-11.—Combination square.
scale by itself or with any one of the following components:
— The center head (2), when attached to the slotted rule, bisects a 90-degree angle. It is used to determine the center of a cylindrical object.
— The protractor head (3) has a level (4) and a
revolving turret (5) that is graduated in degrees from 0
to 180 or 0 to 90 in either direction. It is used to lay out
and measure angles to within one degree.
— The square head (6) has a level (7), scribe (8),
and 45- (9) and 90-degree sides (10). When it is attached
to the slotted steel rule, it can be used to lay out 45- and
90-degree angles and to check level. The square head
may also be used as a height or depth gauge.
Trammels (fig. 5-12) measure distances beyond
the range of calipers. They also can be used as calipers,
if you have the auxiliary attachments.
The basic trammel consists of two heads (trams).
One head has a device for fine adjustments. The
wooden beam must be made by the HT as it is not
provided by the manufacturer. You can attach divider
points, caliper legs, and ball points to the tram. The
ball points with holder are used for scribing or
measuring from the center of a hole.
Figure 5-12.—Trammels.
Figure 5-14.—Parts of an auger bit.
Figure 5-15.—Types of screw points.
Figure 5-13.—Drill bits.
The spurs function to score the outer edge of the
chip as the cutting lips chisel or cut the waste material
loose. The spurs and cutting lips must be sharp to
produce a smooth hole.
The twist of the auger bit is responsible for removing waste material after being cut by the spurs and
cutting lips. It is slightly smaller in diameter than the
head. The twist comes in three styles—single twist with
solid center, single twist, and double twist.
The wood-boring bits and drills usually found in the
HT shop are shown in figure 5-13—included are the
auger bit, expansion bit, twist bit, machine spur bit, and
multispur bit.
The single twist with solid center clears chips
more rapidly, is stronger, and is more common
than the single or double twist.
The auger bit (fig. 5-13, view A) is the most common of the wood-boring bits. It should be used with a
hand brace. It consists of three parts: the head, twist, and
shank, as shown in figure 5-14.
The screw point functions to center the bit and to
pull the bit through the stock. The three types of screw
points are coarse, medium, and fine (fig. 5-15). The
coarse bit is drawn through the stock faster than a fine
one, but there is more roughness because of the faster
The single twist has less tendency to bind in
certain materials but is more fragile than the
single twist with solid center.
The double twist produces a clean, smooth,
accurate hole and bores slower than other
twist bits. It is the most suitable of the three to
bore holes for wooden dowels.
expansive, bit (fig. 5-17). The expansion bit consists
of a screw point, the body cutting edge, and three
adjustable cutter blades. The blades let you bore holes
up to 4 inches in diameter. The adjustable cutter blade
adjusts by either a microdial (fig. 5-17) or a simple
screw arrangement. Make a trial cut on scrap stock
after adjusting an expansion bit to make sure that the
bit is cutting the exact diameter desired.
The shank is that part of the auger bit that fits into
the chuck of the brace. It has the drill size number
stamped on one of the flats of the square-tapered tang.
This number represents the drill size in sixteenths of an
inch (fig. 5-16). For instance, if the number stamped on
the flat is 12, the drill size is 12/16 inch or 3/4 inch. All
bits having a tang-type shank are numbered and sized
in this manner.
Auger bits usually come in sets containing 1/4-inch
(#4) to 1-inch (#16) bits, but they are available up to 2
inches (#32) in diameter. Many different lengths of
auger bits are available and come in three sizes. The
dowel bit is about 5 inches long. The medium bit is
about 8 inches long and the ship bit is from 18 to 24
inches long. The medium bit is the length most commonly used.
The twist drill bit (fig. 5-13, view C) is used to bore
holes 1/2 inch and under. They work with any type of
drill. High-carbon or high-speed steel twist drills are
used for low-speed metal boring or high-speed wood
boring. The high-speed steel drill is for high-speed
metal boring.
Twist drills come in several styles. The styles are
differentiated by the shank. The part of the twist drill
that fits into the socket, spindle, or chuck of the drill
press is known as the shank. The three most common
types of shanks are shown in figure 5-18.
Another bit designed for use with the brace and to
bore holes larger than 7/8 inch is the expansion, or
Figure 5-16.—Size markings on auger bits.
Figure 5-17.—Expansion bit.
Figure 5-18.—Three most common types of shanks.
Table 5-1.—Twist Drill Sizes
Twist drills have various shank types sized by fraction, number, or letter. Fraction symbols give the actual
size of the drill. Sets that include sizes from 1/16 to 1/2
inch are common in the shop. Number and letter designators only identify the drill. A drill gauge or reference
chart (table 5-1) gives the actual size of the drill. Note
that the letter sizes are larger and start where the number
sizes stop. The most common type used in HT shops is
the carbon steel drill with a straight shank.
Figure 5-21.—Comparison of a twist drill for plastic and a
twist drill for metal.
A drill should be reground at the first sign of dullness. The increased load that dullness imposes on the
cutting edges may cause a drill to break.
may fall on them. Do not place drills where they will
rub against each other.
Twist drills are sharpened differently for boring
different materials. The two common angles are the
regular point (fig. 5-19) and the flat point (fig. 5-20).
The regular point has an angle of 118° and is used for
general boring, which includes wood and metal. The flat
point has an angle of 135° and is used to bore hard and
tough materials.
The machine spur bit (fig. 5-13, view E) works
only in a drill press. It is a high-speed, smooth-cutting
bit for boring deep, flat-bottomed holes. It has a
centering point and a twist to remove waste material
and comes in sizes ranging from 1/8 to 1/2 inch in
The general-purpose twist drill is made of highspeed steel. Figure 5-21 shows a typical plastic-cutting
drill and a typical metal-cutting drill. Notice the smaller
angle on the drill used for drilling plastics.
Before putting a drill away, wipe it clean and give
it a light coating of oil. Do not leave drills in a place
where they may be dropped or where heavy objects
The multispur bit (fig. 5-13, view F) also works
strictly in drill presses. Use it to bore flat-bottomed
holes larger than the machine spur bit and ranges in
size from 1/2 to 4 inches in diameter.
NOTE: As bit sizes increase, drill press speed
The countersink forms a seat for the head of a
flat-headed wood screw and comes in three types (fig.
5-22). Type A is for use with a hand brace. Types B
Figure 5-19—Specifications for grindinga regular point
twist drill.
Figure 5-20.—Specifications for grinding a flat point twist
Figure 5-22.—Types of countersinks.
and C are used in either the hand drill, portable electric
drill, or drill press. Type B produces a rough surface
but cuts the fastest. Type C produces a smooth seat and
is the countersink of choice for finish work.
There are many types of combination countersinks and counterbores, but they all perform the same
function. These tools make the pilot hole, shank
clearance, and countersink in one operation. The
combination counterbore performs the same tasks as
the combination countersink and bores a plug hole for
wooden plugs. Combination countersinks and
counterbores range in size from #6 to #12 and
accommodate wood screw sizes #5 to #14.
The particular size of wood screw each countersink and counterbore accommodates determines the
size of the countersink or counterbore. Use both with
the hand drill, portable electric drill, and drill press.
Figure 5-23.—Types of points on the metal-cutting chisel.
the job. Be sure to use a hammer that matches the
chisel; that is, the larger the chisel, the heavier the
hammer. A heavy chisel will absorb the blows of a
light hammer and will do virtually no cutting. As a
general rule, you should hold the chisel in your left
hand with the thumb and first finger about 1 inch from
the top. You should hold it steady but not tight. Your
finger muscles should be relaxed, so if the hammer
strikes your hand it will permit your hand to slide
down the tool and lessen the effect of the blow. Keep
your eyes on the cutting edge of the chisel, not on the
head, and swing the hammer in the same plane as the
body of the chisel. If you have a lot of chiseling to do,
slide a piece of rubber hose over the chisel. This will
lessen the shock to your hand.
There are many types of metal-cutting tools used
by skilled mechanics of all ratings. As you become
better acquainted with your rating, you will probably
discover many tools that you use for cutting metal that
are not described in this chapter. In this chapter, only
the basic hand metal-cutting tools (chisels, hacksaws,
and files) will be discussed due to their frequent but
incorrect use.
Chisels are tools that can be used for chipping or
cutting metal. They will cut any metal that is softer
than the materials of which they are made. Chisels are
made from a good grade tool steel and have a hardened
cutting edge and beveled head. Cold chisels are
classified according to the shape of their points, and
the width of the cutting edge denotes their size. The
most common shapes of chisels are flat (cold chisel),
cape, round nose, and diamond point (fig. 5-23).
When using a chisel for chipping, always wear
goggles to protect your eyes. If other people are
working close by, see that they are protected from
flying chips by erecting a screen or shield to contain
the chips. Remember that the time to take these
precautions is before you start the job.
The type of chisel most commonly used is the flat
cold chisel that cut rivets, split nuts, chip castings, and
cut thin metal sheets. The cape chisel is used for
special jobs like cutting keyways, narrow grooves, and
square corners. Round-nose chisels make circular
grooves and chip inside comers with a fillet. Finally,
the diamond-point is used for cutting V-grooves and
sharp comers.
After numerous blows to the head of a chisel, it
will begin to deform. This deformation is called
mushrooming and creates a very dangerous situation.
If the head of a chisel mushrooms excessively, bits of
the head will begin to fly off when struck with a
hammer. These small bits of metal have the force of
shrapnel from a hand grenade and could cause as much
damage. Simply keep the head of a chisel ground down
to remove this dangerous situation.
As with other tools, there is a correct technique for
using a chisel. Select a chisel that is large enough for
A tool kit for nearly every rating in the Navy is not
complete unless it contains an assortment of files.
There are a number of different types of files in
common use, and each type may range in length from
3 to 18 inches.
Files and rasps fall into the abrading tool family.
You only need the half-round file and the half-round
rasp for ordinary work. The most useful sizes are 6, 8,
and 10 inches.
Files are graded according to the degree of
fineness, and according to whether they have singleor double-cut teeth. The difference is apparent when
you compare the files in figure 5-24, view A.
Single-cut files have rows of teeth cut parallel to
each other. These teeth are set at an angle of about 65
degrees with the center line. You will use single-cut
files for sharpening tools, finish filing, and draw
filing. They are also the best tools for smoothing the
edges of sheet metal.
Files with crisscrossed rows of teeth are doublecut files. The double cut forms teeth that are
diamond-shaped and fast cutting. You will use doublecut files for quick removal of metal and for rough
Files are also graded according to the spacing and
size of their teeth, or their coarseness and fineness.
Some of these grades are pictured in figure 5-24, view
B. In addition to the three grades shown, you may use
some DEAD SMOOTH files, which have very fine
teeth, and some ROUGH files with very coarse teeth.
The fineness or coarseness of file teeth is also
influenced by the length of the file. (The length of a
file is the distance from the tip to the heel, and does
not include the tang (fig. 5-24, view C). When you
have a chance, compare the actual size of the teeth of
a 6-inch, single-cut smooth file and a 12-inch,
single-cut smooth file; you will notice the 6-inch file
has more teeth per inch than the 12-inch file.
Figure 5-24.—File information.
TRIANGULAR files are tapered (longitudinally)
on all three sides. They are used to file acute internal
angles and to clear out square corners. Special
triangular files are used to file saw teeth.
Files come in different shapes. Therefore, in
selecting a file for a job, the shape of the finished work
must be considered. Some of the cross-sectional
shapes are shown in figure 5-24, view D.
MILL files are tapered in both width and
thickness. One edge has no teeth and is known as a
safe edge. Mill files are used for smoothing lathe work
draw filing, and other fine, precision work. Mill files
are always single-cut.
FLAT files are general-purpose files and may be
either single- or double-cut. They are tapered in width
and thickness. HARD files, not shown, are somewhat
thicker than flat files. They taper slightly in thickness,
but their edges are parallel. The flat or hard files most
often used are the double-cut for rough work, and the
single-cut, smooth file for finish work.
SQUARE files are tapered on all four sides and
are used to enlarge rectangular-shaped holes and slots.
ROUND files serve the same purpose for round
openings. Small round files are often called “rattail”
Figure 5-25.—Hacksaws.
length is the distance between the two pins that hold
the blade in place.
The HALF-ROUND file is a general-purpose tool.
The rounded side is used for curved surfaces and the
flat face on flat surfaces. When you file an inside
curve, use a round or half-round file whose curve most
nearly matches the curve of the work.
Hacksaw blades are made of high-grade tool steel,
hardened and tempered. There are two types: the
all-hard and the flexible. All-hard blades are hardened
throughout, whereas only the teeth of the flexible
blades are hardened. Hacksaw blades are about
one-half inch wide, have from 14 to 32 teeth per inch,
and are from 8 to 16 inches long. The blades have a
hole at each end that hooks to a pin in the frame. All
hacksaw frames that hold the blades either parallel or
at right angles to the frame are provided with a
wingnut or screw to permit tightening or removing the
Care of Files
You should break in a new file carefully by using
it first on brass, bronze, or smooth cast iron. Just a few
of the teeth will cut at first, so use a light pressure to
prevent tooth breakage. Do not break in a new file by
using it first on a narrow surface. Protect the file teeth
by hanging your files in a rack when they are not in
use, or by placing them in drawers with wooden
partitions. Your files should not be allowed to
rust—keep them away from water and moisture.
Avoid getting the files oily. Oil causes a file to slide
across the work and prevents fast, clean cutting. Files
that you keep in your toolbox should be wrapped in
paper or cloth to protect their teeth and prevent
damage to other tools.
The SET in a saw refers to how much the teeth are
pushed out in opposite directions from the sides of the
blade. The four different kinds of set are
RAKER set, and WAVE set. Three of these are shown
in figure 5-26.
The teeth in the alternate set are staggered, one to
the left and one to the right throughout the length of
the blade. On the double alternate set blade, two
Hacksaws are used to cut metal that is too heavy
for snips or bolt cutters. Thus, metal bar stock can be
cut readily with hacksaws.
There are two parts to a hacksaw: the frame and
the blade. Common hacksaws have either an
adjustable or solid frame (fig. 5-25). Most hacksaws
found in the Navy are of the adjustable frame type.
Adjustable frames can be made to hold blades from 8
to 16 inches long, while those with solid frames take
only the length blade for which they are made. This
Figure 5-26.—“Set” of hacksaw blade teeth.
adjoining teeth are staggered to the right, two to the
left, and so on. On the raker set blade, every third tooth
remains straight and the other two are set alternately.
On the wave (undulated) set blade, short sections of
teeth are bent in opposite directions.
Using Hacksaws
The hacksaw is often used improperly. Although
it can be used with limited success by an inexperienced
person, a little thought and study given to its proper
use will result in faster and better work and less dulling
and breaking of blades.
Good work with a hacksaw depends not only upon
the proper use of the saw, but also upon the proper
selection of the blades for the work to be done. Figure
5-27 will help you select the proper blade to use when
sawing metal with a hacksaw. Coarse blades with
fewer teeth per inch cut faster and are less liable to
choke up with chips. However, finer blades with more
teeth per inch are necessary when thin sections are
being cut. The selection should be made so that, as
each tooth starts its cut, the tooth ahead of it will still
be cutting.
Figure 5-28.—Installing a hacksaw blade.
from the handle of the hacksaw (hand hacksaws cut on
the push stroke.) Tighten the wingnut so that the blade
is definitely under tension. This helps make straight
To make the cut, first install the blade in the
hacksaw frame (fig. 5-28) so that the teeth point away
Place the material to be cut in a vise. A minimum
of overhang will reduce vibration, give a better cut,
and lengthen the life of the blade. Have the layout line
outside of the vise jaw so that the line is visible while
you work.
When cutting, apply pressure on the forward
stroke, which is the cutting stroke, but not on the return
stroke. From 40 to 50 strokes per minute is the usual
speed. Long, slow, steady strokes are preferred.
For long cuts (fig. 5-29) rotate the blade in the
frame so that the length of the cut is not limited by the
depth of the frame. Hold the work with the layout line
close to the vise jaws, raising the work in the vise as
the sawing proceeds.
Figure 5-29.—Making a long cut near the edge of stock.
Figure 5-27.—Selecting the proper hacksaw blade.
C-clamp when necessary. The wood block helps
support the blade and produces a smoother cut. Using
the wood only in back of the metal permits the layout
lines to be seen.
Saw thin metal as shown in figure 5-30. Notice the
long angle at which the blade enters the saw groove
(kerf). This permits several teeth to be cutting at the
same time.
Metal that is too thin to be held, as shown in figure
5-31, can be placed between blocks of wood, as shown
in figure 5-3 1. The wood provides support for several
teeth as they are cutting. Without the wood, as shown
in view B of figure 5-31, teeth will be broken due to
excessive vibration of the stock and because
individual teeth have to absorb the full power of the
Hacksaw Safety
The main danger in using hacksaws is injury to
your hand if the blade breaks. The blade will break if
too much pressure is applied, when the saw is twisted,
when the cutting speed is too fast, or when the blade
becomes loose in the frame. Additionally, if the work
is not tight in the vise, it will sometimes slip, twisting
the blade enough to break it.
Cut thin metal with layout lines on the face by
using a piece of wood behind it (fig. 5-32). Hold the
wood and the metal in the jaws of the vise, using a
You will be using portable power drills, hammers,
and grinders in the shop and out on the job. You should
be thoroughly familiar with the operation and care of
these tools and with applicable safety precautions.
Individual electrically powered hand tools are not
covered in this chapter. However, it is important that
you understand some important safety and operating
procedures for these tools. Only the most common
portable pneumatic power tools will be covered in this
Figure 5-30.—Gutting thin metal with a hacksaw.
Most portable power tools are driven by
electricity. However, the portable power tools that you
use may be powered by electric motors or by air
(pneumatic) motors. Whether electric powered or air
powered, the tools and the procedures for using them
are basically the same. Maintenance information
about portable power tools can be found in the
equipment owner’ s manual.
Figure 5-31.—Cutting thin metal between two wooden blocks.
Several safety and operating precautions must be
observed when you use electrical tools. The most
important of these relate to electrical shock. Electrical
tools are made so all current-carrying parts, except
filters, are insulated from housings and handles. The
tools are laboratory tested to ensure they are safe to
use when new. However, tool abuse (overload or
dropping) could cause a short and you could receive
an electrical shock. You can reduce the electrical
shock hazard by ensuring that there is a grounding
wire between the tool housing and a positive ground.
All electrically powered tools must have a
three-wire cord and be double-insulated. All
Figure 5-32.—Gutting thin metal using wood block with
layout lines.
should be checked for real or potential damage
before each use.
electrically powered hand tools are required to be
stored in the electrical tool issue room so that they may
be checked by an electrician prior to issue. Never use
a portable electric tool that has not been electrically
safety checked by shipboard electricians. Always
follow approved checkout procedures for electrical
tools. A 120-volt shock can kill you.
Ensure work is properly secured prior to operating portable equipment.
Many portable tool housings are made of special
high-impact plastic that is resistant to damage. Plastic
reduces the electrical shock hazard, but it does not
prevent shock hazards completely. To eliminate this
shock hazard when using electrically powered tools,
you should wear approved electrical rubber gloves
(issued with the tool by the electrician). These rubber
gloves should be protected with a pair of leather
gloves over them. Other safety precautions are listed
as follows:
This section deals with pneumatic drills and
pneumatic grinders since these are probably the most
widely used portable power tools. You will be
required to maintain the portable pneumatic tools that
you will be using.
Since pneumatic tools use compressed air, all
low-pressure compressed air systems should have a
filter, regulator, and lubricator assembly installed at
the outlet. This assembly will ensure delivery of clean,
regulated, mist-lubricated compressed air for the
operation of pneumatic tools. The pressure must not
exceed 90 psi for any pneumatic tool. CAUTION:
Never point the air hose at another person.
When using an electric tool, make sure it is
properly grounded. Use only three-wire
grounded cords and plugs.
Before operating a pneumatic drill, inspect the air
hose and check for any leaks and damage. Blow air
through the air hose to free it of foreign material before
connecting it to the drill. Keep the air hoses clean and
free from excessive amounts of lubricants.
When an extension cord must be used in addition to the cord on an electric tool, the extension cord must not be energized when the tool
plug is inserted in or removed from the extension cord. Extension cords also must have
three-wire cords and grounded plugs. Extension cords may only be 25 feet in length for
shipboard use.
The heavy duty pneumatic drill, shown in view A
of figure 5-33, is reversible. Its speed can be closely
controlled by the throttle valve located in the handle.
The variable speed feature of this drill makes it
particularly useful for heavy duty drilling in places
that are hard to reach.
All portable electrical tools and extension
cords require a periodic safety check for shorts
or grounds. The tool housing, cord, and plug
Figure 5-33.—Heavy duty pneumatic drill and stand.
Another feature of this drill is a feed screw that
can be used with a special type of drill stand called an
“old man.” This drill stand is shown in view B of figure
5-33. To drill a hole using the “old man,” first place
the twist drill in the socket. Adjust the feed screw in
the machine to its lowest position and place the point
of the feed screw in one of the indentations in the arm.
Drill the hole to the required depth. Watch the drill;
when it begins to come through. decrease the speed.
Hold the drill motor up by hand so that it will not drop
onto the work.
The pneumatic grinder, shown in figure 5-34,
operates on the same basic principle as the pneumatic
drill. It can be equipped with either a grinding wheel
or a wire bristle wheel. After attaching the appropriate
wheel, perform the preliminary steps required to
connect the pneumatic grinder. Always run this
machine so that the grinding surface of the wheel is
square with the surface of the material being ground.
Do not grind soft nonferrous metals, such as aluminum
or brass, on a wheel that is designed for carbon and
alloy steels. A silicon carbide abrasive wheel is
suitable for grinding soft nonferrous metals,
nonmetallic materials, and cemented carbides. Make
sure that the rpm rating on the wheel is greater than
that of the grinder. If the rpm rating of the grinder is
greater than the wheel, the wheel stands a good chance
of shattering and causing personnel injury from flying
In recent years, we have started using several new
types of pneumatic tools that are used for the setting
of rivets and fasteners. As a result, rivets and fasteners
can now be set easier and faster. The tools shown in
figure 5-35 are relatively easy to operate, and you need
to remember only the few simple precautions
described in the following paragraphs.
Pneumatic tools must have thorough lubrication.
The moving parts of a pneumatic tool are very closely
Figure 5-35.—Pneumatic rivet setting tools.
Figure 5-34.—Sectional view of a pneumatic grinder.
fitted. If proper lubrication is neglected, they wear
rapidly and fail within a short time.
Internal threads are cut with taps and tap
wrenches. External threads are cut with dies and die
stocks. All threads are not alike. They must be
designed, selected, and cut to fit the job. As an HT,
you will be concerned with two types of threads:
machine threads and pipe threads.
Valves and pistons on pneumatic hammers require
a light machine oil. Since the compressed air comes
directly in contact with these parts, it has a tendency
to drive the lubricant out through the exhaust.
Therefore, when working steadily with any pneumatic
tool, you should regularly check the lubricator. Make
certain there is plenty of lubricant, and empty the filter
assembly when needed. On low-pressure compressed
air systems that do not have the filter, regulator, and
lubricator assembly, you should disconnect the air
hose every hour or so and squirt a few drops of light
oil into the air hose connection. Heavy oil will cause
precision parts to clog up and fail. If this happens, you
will have to clean your tool in cleaning solvent to
loosen the gummy substance. Then blow out the tool
with air, lubricate it with a light oil, and go back to
Dies and taps for cutting machine threads are now
made according to three basic sets of standards:
American National, American Standard, and Unified
Thread Standard (also referred to as “the standard”).
Knowing just what these standards are is important.
The AMERICAN NATIONAL standards were
widely used for many years. There are two series of
American National machine threads with which you
will be concerned. These are the American National
Fine (NF) and the American National Coarse (NC)
series. The form of the thread is the same for both
National Fine and National Coarse; the difference is
in the pitch or number of threads to the inch.
Keep your pneumatic tools clean and lubricated,
and you will have fewer operating troubles.
The second set of standards for threads is the
AMERICAN STANDARD. The American Standard
threads for machine screws are based on the older
American National Standard. The two sets of
standards are not identical, but some of the American
Standard threads are identified by the old American
National designation. For example, the American
Standard Fine series is designated by NF and the
American Standard Coarse series by NC.
When using portable pneumatic power tools, there
are certain safety precautions that you must observe.
Always wear your goggles and hearing protection when working with these tools.
Take care not to allow any of these tools to run
out of hand. The pneumatic grinder especially
will want to “walk” away from the point you
want to grind.
The third set of standards is the UNIFIED
THREAD STANDARD. This standard was agreed to
by the United States, Canada, and the United Kingdom
in 1948. It is expected that the Unified Thread
Standard will become the generally accepted standard
for machine threads, replacing the American Standard
and the American National.
Always stand so that your feet won’t slip
while you are working. Make sure that you are
properly balanced.
Apply the grinding wheel to the work with
gentle pressure. Sudden forcing may cause the
wheel to shatter. As you complete the work,
ease up on the pressure.
Many of the machine threads using these three
basic standards are interchangeable; they are either
identical or very similar in general form. The major
differences between the Unified Thread Standard and
the earlier standards are in the application of
allowances, the variation of tolerance with size, the
amount of pitch diameter tolerance, and the
designation of the threads. In general, the Unified
Thread Standard provides more classes of fit than did
the earlier standards.
Be careful not to allow the air hose to become
Pneumatic grinders and sanders turn at a high
rpm. Use only the approved type of grinding
wheel or disk. The maximum operating rpm is
shown on the side of the wheel or disk. Remember the rpm rate of the wheel must be
higher than the rpm rate of the grinder or
sander. Using a wheel with a lower rpm rate
than the tool can cause the wheel to shatter.
Pipe taps and dies differ from machine taps and
dies in that most pipe threads are tapered to provide
an airtight and liquid-tight seal. Pipe diameters are
measured as inside diameters; therefore, the wall
thickness of the pipe must be taken into consideration.
This means the pipe taps and dies are larger in
diameter than the machine taps and dies. In other
words, a 1/2-inch pipe tap or die is larger in diameter
than a 1/2-inch machine tap or die.
The NPT, which formerly stood for National Pipe
Thread, is still used as a carryover and now refers to the
new name for the same thread, American Standard
Taper Pipe Threads. The standard taper of pipe threads
is three-fourths inch per foot. The number of threads per
inch varies according to the size of pipe as follows:
l/16- and 1/8-inch pipe have 27 threads per
1/4- and 3/8-inch pipe have 18 threads per
1/2- and 3/4-inch pipe have 14 threads per
1-, 1 1/4-, 1 1/2-, and 2-inch pipe have 11 1/2
threads per inch
2 1/2-inch pipe and pipe larger than 2 1/2
inches have 8 threads per inch
Hand pipe-threading tools are supplied by the
Navy to cut external threads up to 4 inches and internal
threads up to 4 inches. However, hand pipe-threading
tools that will cut pipe up to 12 inches can be
requisitioned through the supply department. Pipe
over 3 inches in diameter is normally joined by
oxyacetylene welding, arc welding, or by brazing with
silver-base or copper-base alloys.
Figure 5-36.—Types of common taps.
This section of the chapter contains instructions
on how to select and use the taps and drills for the
various standard thread sizes. You will also find a
detailed explanation of how to use taper, plug, and
bottoming taps, how to cut machine threads with taps
and dies, and how to lubricate the work.
The taper (starting) hand tap has a chamfer length
of 8 to 10 threads. These taps are used when starting
a tapping operation and when tapping through holes.
Plug hand taps have a chamfer length of 3 to 5
threads and are designed for use after the taper tap.
Bottoming hand taps are used for threading the
bottom of a blind hole. They have a very short chamfer
length of only 1 to 1 1/2 threads for this purpose. This
tap is always used after the plug tap has already been
used. Both the taper and plug taps should precede the
use of the bottoming hand tap.
Taps and dies are used to cut threads in metal,
plastics, or hard rubber. The taps are used for cutting
internal threads, and the dies are used to cut external
threads. There are many different types of taps.
However, the most common are the taper, plug,
bottoming, and pipe taps as shown in figure 5-36.
Pipe taps are used for pipe fittings and other places
where extremely tight fits are necessary.
5-37) will cut American Pipe Thread only. It comes in
a variety of sizes for cutting threads on pipe with
diameters of 1/8 inch to 2 inches.
The tap diameter, from end to end of threaded
portion, increases at the rate of 3/4 inch per foot. All
the threads on this tap do the cutting, as compared to
the straight taps where only the nonchamfered portion
does the cutting.
A rethreading die as shown (fig. 5-37) is used
principally for dressing over bruised or rusty threads
on screws or bolts. It is available in a variety of sizes
for rethreading American Standard Coarse and Fine
threads. These dies are usually hexagon in shape and
can be turned with a socket, box, open-end, or any
wrench that will fit. Rethreading dies are available in
sets of 6, 10, 14, and 28 assorted sizes in a case.
Dies are made in several different shapes and are
of the solid or adjustable type. The square pipe die (fig.
Round split adjustable dies (fig. 5-38) are called
“button” dies and can be used in either hand diestocks
or machine holders. The adjustment in the screw-adjusting type is made by a fine-pitch screw that forces the
sides of the die apart or allows them to spring together.
The adjustment in the open adjusting types is made by
three screws in the holder, one for expanding and two
for compressing the dies. Round split adjustable dies are
available in a variety of sizes to cut American Standard
Coarse and Fine threads, special form threads, and the
standard sizes of threads that are used in Britain and
other European countries. For hand threading, these
Figure 5-37.—Types of solid dies.
Figure 5-38.—Types of adjustable dies.
Two-piece rectangular pipe dies (fig. 5-38)
are available to cut American Standard Pipe threads.
They are held in ordinary or ratchet-type diestocks (fig.
5-40). The jaws of the dies are adjusted by setscrews.
An adjustable guide keeps the pipe in alignment with
respect to the dies. The smooth jaws of the guide are
adjusted by a cam plate; a thumbscrew locks the jaws
firmly in the desired position.
dies are held in diestocks, as shown in figure 5-39. One
type of die stock has three pointed screws that will hold
round dies of any construction, although it is made
specifically for open adjusting-type dies.
Two-piece collet dies (fig. 5-38) are used with a
collet cap (fig. 5-39) and collet guide. The die halves
are placed in the cap slot and held in place by the guide
that screws into the underside of the cap. The die is
adjusted by setscrews at both ends of the internal slot.
This type of adjustable die is issued in various sizes to
cover the cutting range of American Standard Coarse,
Fine, and special form threads. Diestocks to hold the
dies come in three different sizes.
Threading sets are available in many different combinations of taps and dies, together with diestocks, tap
wrenches, guides, and necessary screwdrivers and
wrenches to loosen and tighten adjusting screws and
Figure 5-39.—Diestocks, diecollet, and tap wrenches.
Figure 5-40.—Adjustable die guide and ratchet diestocks.
bolts. Figure 5-41 shows typical threading sets for pipe,
bolts. and screws.
Never attempt to sharpen taps or dies. Sharpening
of taps and dies involves several highly precise cutting
processes, which involve the thread characteristics and
chamfer. These sharpening procedures must be done by
experienced personnel to maintain the accuracy and the
cutting effectiveness of taps and dies.
Keep taps and dies clean and well oiled when not
in use. Store them so that they do not contact each other
or other tools. For long periods of storage, coat taps and
dies with a rust preventive compound, place in individual or standard threading set boxes, and store in a dry
Thread chasers are threading tools that have several
teeth and are used to rethread (chase) damaged external
or internal threads, as shown in figure 5-42. These tools
are available to chase standard threads. The internal
thread chaser has its cutting teeth located on a side face.
The external thread chaser has its cutting teeth on the
end of the shaft. The handle end of the tool shaft tapers
to a point.
Figure 5-42.—Thread chasers.
Threads are helical ridges cut into screws, nuts,
bolts, or the walls of a hole, so that the action of turning
the screw, nut, or bolt gives it endwise as well as rotary
motion. Many thread types exist. These types include
bolt threads, machine screw threads, and pipe threads.
Before we proceed with descriptions of thread-cutting
procedures, we must become familiar with the
terminology to be used.
Thread Terminology
Refer to figure 5-43 and note that the outside
diameter of a thread is known as the MAJOR
Figure 5-41.—Threading sets.
Figure 5-43.—Thread terminology.
Figure 5-46.—Oversize drilled hole for tapping.
percent of the difference between the major and minor
diameters, subtracted from the major diameter.
When the tap hole is the right size, it is a little
larger than the root diameter of the tap, as shown in
figure 5-45. The tap will cut a thread in the work which
is only 75 percent as deep as the thread on the tap. The
other 25 percent of the depth of thread on the tap
provides clearance between the tap hole and the root
diameter of the tap (see fig. 5-45). This makes tapping
Figure 5-44.—Tap drill size determination.
DIAMETER. The diameter across the roots of the
thread is called the MINOR DIAMETER. The PITCH
is defined as the distance from any point on the thread
of a screw to the corresponding point on an adjacent
thread. It is usually measured from crest to crest and
is expressed by a specific quantity of threads per inch.
If the tap drill selected is oversize, the tap hole will
be oversize, and the tap can cut only shallow threads
in the work, as shown in figure 5-46. With less than a
full 75 percent depth of thread, stud or capscrew
threads usually strip.
Tap Drill Determination
If a threaded hole is to be made in a piece of metal,
a hole of suitable size must first be drilled. The hole
must be somewhat smaller than the size of the bolt to
be screwed into it.
If the tap drill selected is undersize, the tap hole
will be undersize, being perhaps equal to the root
diameter of the tap, as shown in figure 5-47. Then
there will be no clearance, and the tap will turn hard,
tear the threads, and probably break.
How do you determine how much smaller to drill
this hole? Figure 5-44 shows the system used for
figuring this. The resultant thread is known as a “75
percent thread” because the diameter of the hole is 75
The best method to determine the exact size of tap
drill to use is to refer to table 5-2. A chart similar to
this generally is included with a set of taps and dies.
Figure 5-47.—Undersize drilled hole for tapping.
Figure 5-45.—Proper size drilled hole for tapping.
Table 5-2.—American National Form Threads
Figure 5-50.—Tapping a blind hole with a taper tap.
immediately. Back the tap up a quarter turn to break
the chips, clean them out of the flutes with a wire (as
shown in fig. 5-49), add some more lubricant, and
continue tapping. When the tap has cut threads
through the hole, the tap will turn with no resistance.
Figure 5-48.—Using a square to ascertain a tap is square with
the work.
Cutting Machine Threads With Taps
To tap a blind hole, start with the taper tap. For a
blind hole you will need all three types—the taper,
plug, and bottoming taps. Be sure they are the size and
thread series you need, and that the tap hole is the size
called for by the working drawing and table 5-2.
Mineral lard oil, applied with a small brush, is
highly recommended as a lubricant when tapping in
steel. When using this lubricant, tighten the tap in the
tap wrench and apply the lubricant to the tap. Start the
tap carefully with its axis on the center line of the hole.
The tap must be square with the surface of the work,
as shown in figure 5-48.
Begin with the taper tap. Handle it as described
earlier. Figure 5-50, view A, shows the taper tap just
starting to cut. In figure 5-50, view B, it has cut a little
farther. In figure 5-50, view C, it has bottomed in the
hole after having cut several full threads near the top
of the hole. This completes the work to be done with
the taper tap.
To continue tapping, turn the tap forward two
quarter turns, back it up a quarter turn to break the
chips, and then turn forward again to take up the slack.
Continue this sequence until the required threads are
cut. After you cut for the first 2 or 3 full turns, you no
longer have to exert downward pressure on the
wrench. You can tell by the feel that the tap is cutting
as you turn it. Don't permit chips to clog the flutes or
they will prevent the tap from turning. When the tap
won’t turn and you notice a springy feeling, stop trying
In figure 5-51, view A, the plug tap has entered
the few full threads cut by the taper tap. In figure 5-51,
view B, it has continued these threads a little farther
down into the hole. In figure 5-51, view C, it has
bottomed in the hole. This is all the work that you can
do with the plug tap. It has cut full threads about
halfway down the tap hole before bottoming.
Figure 5-49.—Using a wire to clear chips from the flute of a
Figure 5-51.—Tapping a blind hole with a plug tap.
In figure 5-52, the bottoming tap has been substituted for the plug tap. In figure 5-52, view A, it has been
run down the full threads cut by the plug tap and is ready
to cut more full threads. In figure 5-52, view B, it has
cut a few more threads, and in figure 5-52, view C, it
has bottomed in the hole. The blind hole has now been
completely tapped.
Because these threads are being tapped in a blind
hole, you must remove chips differently. To remove
chips, back the tap completely out of the hole very
frequently, invert the stock, if possible, and jar out the
chips or work them out of the hole with a wire while the
stock is in the inverted position.
Chip removal in tapping blind holes is much more
difficult to do and is very important because chips will
fal1 ahead of the tap through the flutes and accumulate
in the bottom of the blind hole. Until these chips are
removed, none of the three taps can complete its work.
In tapping blind holes, alternate with tapping and chip
removal until each of the three taps bottom in the blind
When you have finished using the three taps, brush
the chips out of their teeth, oil them well with lubricating oil, wipe off the surplus oil, and replace them in the
threading set.
Before using any machine tool, you must be familiar with all safety precautions pertaining to its operation.
Carelessness around any moving machinery is extremely dangerous. When moving machinery is
equipped with sharp cutting tools, the dangers are
greatly increased. The following list includes some of
the more general safety precautions for machine tools.
Specific safety precautions should be posted in plain
sight by every machine.
Do not lean against any machine that is in
motion. Keep clear of all gears, belts, and
other moving parts. Never remove the guards
from any part of an operating machine.
Never start a machine unless you are thoroughly familiar with its operation.
Do not attempt to clean, adjust, or repair a
machine while it is in motion. NEVER attempt
to clean running gears.
PROTECT YOUR EYES. Do not hold your
head too close to the cutting tool. Flying bits
of metal or scale may get into your eyes.
Always wear goggles when there is any danger of flying particles getting in your eyes—
for example, when using a grinding or drilling
The Navy furnishes modern equipment to help
you perform your duties. This section introduces you
to some of the most common machine tools found in
workshops that you should be familiar with. A
machine tool is a power-driven machine that holds the
material and cutting tool and brings them together so
the material is drilled, cut, shaved, or ground.
appropriate hearing protection. Either audio
headsets or ear plugs will filter the noise from
running machinery. Prolonged exposure may
damage your hearing.
Keep your fingers away from the cutting
edges when the machine is in operation. Otherwise, you could lose some fingers.
The machine tools described in this chapter are
found in most well-equipped shops. Other machine
tools for specific types of work will be described in their
appropriate chapter of this training manual.
Do not wear gloves or loosely hanging
clothes. They can be caught by moving parts
of the shop machinery and cause serious injuries. Keep your sleeves rolled up tightly above
the elbows. Do not wear neckties or loose
In all machine work, stress SAFETY first,
ACCURACY second, and SPEED last. Excessive speed is both dangerous and inefficient.
Metal-cutting saws are standard equipment in repair facilities. They are used for nonprecision cutting of
Figure 5-52.—Finish tapping a blind hole with a bottoming
Figure 5-53.—Power hacksaw.
various metals and can cut any reasonable size or shape.
In the pipe shop, bandsaws are used to cut pipe and
tubing for various types and sizes at different angles. In
the shipfitter shop, metal-cutting saws are used to cut
angle iron, pipe, zincs, bar stock, and numerous other
stock. In the carpenter shop, saws are used to cut
wooden patterns, miter frames, stock, and for other
similar applications. Metal-cutting saws can cut brass,
bronze, aluminum, Monel, and thin sections of carbon
steel casting and other types of metals.
Since the metal-cutting saw cuts materials of
varying thickness, toughness, and hardness, you must
select the proper blade for each job. Blade design and
particular job is determined by the size and material
composition of the section and the material to be cut.
Use coarse pitch teeth for wide, heavy sections to
provide ample chip clearance. For thinner sections,
use a blade with a pitch that will keep two or more
teeth in contact with the work so that the teeth will not
straddle the work and strip the teeth. In general, you
should select blades according to the following
uses are presented later in this chapter to help you
understand the differences in blades.
The power hacksaw (fig. 5-53) is found in all
except the smallest shops. It is used to cut bar stock,
pipe, tubing, or other metal stock. It consists of a base,
a mechanism for causing the saw frame to reciprocate,
and a clamping vise for holding the stock while it is
being sawed. There are two types of power hacksaws:
the direct mechanical drive and the hydraulic drive.
Coarse (4 teeth per inch) for soft steel, cast
iron, and bronze
The power hacksaw shown in figure 5-53 has a
capacity of 4" × 4". This means it can handle material
up to 4 inches wide and 4 inches high.
Regular (6 to 8 teeth per inch) for annealed
high-carbon steel and high-speed steel
A power hacksaw will have one of three typos of
feed mechanisms:
Medium (10 teeth per inch) for solid brass
stock, iron pipe, and heavy tubing
Mechanical feed, which ranges from 0.001 to
0.025 inch per stroke, depending upon the
class and type of material being cut
Fine (14 teeth per inch) for thin tubing and
sheet metals
Hydraulic feed, which normally exerts a constant pressure, but is designed so that the feed
stops automatically at hard spots to decrease
the pressure on the saw until the hard spot has
been cut through.
Speed for hacksaws is stated in strokes-per-minute,
counting only those strokes that cause the blade to make
a cut on the stock are counted. A gear shift lever is used
to change speeds. There may be a card attached to or
near the saw giving recommended speeds for cutting
various metals. However, you may use the following
Gravity feed, in which weights are placed on
the saw frame and shifted to give more or less
pressure of the saw blade against the material
being cut.
— Cold-rolled or machine steel, brass, and soft
metals—136 strokes per minute.
All three types of feed mechanisms lift the blade
clear of the work during the return stroke.
— Alloy steel, annealed tool steel, and cast iron—
90 strokes per minute.
Hacksaw Blades
— High-speed steel, unannealed tool steel, and
stainless steel—60 strokes per minute.
The blade shown in figure 5-54 is especially
designed for use with the power hacksaw. It is made
with a tough alloy steel back and high-speed steel
teeth. This combination gives both a strong blade and
a cutting edge suitable for high-speed sawing.
You should use a coolant for most power hacksawing operations. (Cast iron should be dry when it is cut.)
The coolant prevents overheating of the blade and stock
along with increasing the cutting rate. A soluble oil
solution with a mixture of the oil and water will be
suitable for most sawing operations. The normal mixture for soluble oil is 40 parts water to 1 part oil. You
also may use a synthetic coolant.
These blades vary as to the pitch of the teeth
(number of teeth per inch). The correct pitch for a
Metal-cutting bandsaw machines are standard
equipment on all repair ships and tenders. These
Figure 5-54.—Power hacksaw blade.
machines can be used for nonprecision cutting similar
to that performed by power hacksaws. Some types can
also be used for precision cutting, filing, and polishing.
A bandsaw machine is more flexible for straight cutting
than a power hacksaw in that it can cut objects of any
reasonable size and of regular and irregular shapes. A
power hacksaw has a more limited capacity; it can only
cut pieces with regular shapes. Also, the bandsaw cuts
much faster than the hacksaw because the cutting action
of the blade is continuous.
Figure 5-55 shows a tiltable blade bandsaw. The
blade may be set either upright or at any angle up to 45
degrees from the vertical. The work is held stationary
in a vise and the blade is moved into the work.
Figure 5-56 shows a tiltable table bandsaw. On the
type shown, you should feed work either manually or
by power to the blade, which runs in a fixed position.
During recent years, the tiltable table bandsaw has been
installed in most repair shops on repair ships and tenders.
A third type of bandsaw is designed for heavier
work and has neither a tiltable blade nor a tiltable table.
You will find this type on some ships.
Many of the new models, such as the one shown in
figure 5-56, also have a job selector mounted on the
machine. The names of various materials are inscribed
on the outer ring of the selector. This ring is movable
and can be positioned so that the name of any specific
material can be brought into alignment with the window
slot at the bottom of the dial. The numbers or letters that
Figure 5-56.—Tiltable table-type (contour) metal-cutting
appear in the window, read in conjuction with stationary
entries on the dial face, give the correct saw pitch, set
and temper, saw velocity, and power feed pressure
needed to cut that particular material.
Another type of metal-cutting bandsaw is shown in
figure 5-57. This horizontal band cutoff saw is being
used in shops on some ships to replace the reciprocating-type power hacksaw. The continuous cutting action
of the blade provides greater speed, accuracy, and versatility.
Figure 5-57.—Horizontal band cutoff saw.
Figure 5-55.—Tiltable blade metal-cutting bandsaw.
GAUGE: The thickness of a blade. This measurement is expressed in thousandths of an inch. Saw
bands come in three gauges—0.025, 0.032, and 0.035
Good results from the use of any metal-cutting
bandsaw depends upon the careful choice of a blade.
Tooth pitch should be considered in relation to the
hardness and toughness of the material being worked,
and the thickness of the workpiece. At least two teeth
should be in contact with the work at all times during
the cutting operation. When you cut thick material,
select a tooth pitch that allows the smallest possible
number of teeth to be in contact with the material.
More teeth in contact means that a greater feed
pressure is required to force them into the material.
Excessive feed pressure will cause the cut to be off the
SET: The bend or spread given to the teeth to
provide clearance for the body of the blade when you
make a cut.
SIDE CLEARANCE: The difference between the
dimension of the gauge of the blade and the set of the
teeth. Side clearance provides running room for the
body of the blade in the kerf or cut. Without side
clearance, the saw band will bind in the kerf.
SET PATTERN: One of three distinct patterns
(raker, wave, and straight) in which teeth are set. The
raker set pattern is used to cut solid cross-section
work. The wave set pattern is used to cut hollow
materials, such as pipes and tubing. The straight set
pattern is not used to any great extent to cut metal.
Saw Bands
A saw band has the following characteristics,
which are illustrated in figure 5-58.
PITCH: The number of teeth per linear inch. Every
saw blade has a specific even number of teeth per
linear inch. Normally this is from 6 to 32 teeth per inch
of blade.
TEMPER: The degree of hardness of the teeth,
indicated by the letters A and B, with temper A being
the harder. The A or B designation will only be found
on the container the blade was shipped in. Temper A
saw blades are used for practically all bandsaw
metal-cutting work.
WIDTH: The distance across the flat surface of the
saw band (back to the tip of the tooth). The width
measurement is always expressed in inches or
fractions of an inch. Blades are available in widths up
to 1 inch.
Grinders are simple machines that allow you to
reshape, form, and sharpen metal-cutting tools, or
other tools. The type of grinder discussed in this
chapter is the pedestal grinder.
The main parts of a pedestal grinder are as follows:
A motor with an extended shaft for mounting
grinding wheels.
A mounting base for the motor.
An adjustable tool rest for steadying the work
piece for grinding.
Wheel guards mounted over the grinding
wheel as a safety feature.
A shield fastened to the wheel guards to protect the operator from flying chips
The pedestal grinder is one of the most common and
versatile machine found in most shops. You will probably use this piece of equipment more than any other
piece of equipment found in your shop. You will use it
to clean welds, remove burrs, sharpen tools, dress up
Figure 5-58.—Saw band characteristics.
torch cuts, buff sheet metal, and for numerous other
functions. Not only must you be able to use a pedestal
grinder, but you also must observe all important operating and safety precautions.
— Use a coolant to prevent overheating the work.
— Wear goggles and respiratory filters to protect
your eyes and lungs from injury by grit and dust generated by grinding operations.
Grinding Safety
— Transparent shields, if installed, should be
clean and properly adjusted. Transparent shields do not
preclude the use of goggles as the dust and grit may get
around a shield. Goggles, however, provide full eye
The grinding wheel is a fragile cutting tool that
operates at high speeds. Therefore, the safe operation of
pedestal grinders is as important as proper grinding
techniques. Observance of posted safety precautions is
mandatory for the safety of the operator and the safety
of personnel in the nearby vicinity.
What are the most common sources of injury during
grinding operations? Hazards leading to eye injury
caused by grit generated by the grinding process are the
most common and the most serious. Abrasions caused
by bodily contact with the wheel are quite painful and
can be serious. Cuts and bruises caused by segments of
an exploded wheel, or a tool “kicked” away from the
wheel are other sources of injury. Cuts and abrasions
can become infected if not protected from grit and dust
from grinding.
Safety in using pedestal grinders is primarily a
matter of using common sense concentrating on the job
at hand. Each time you start to grind a tool, stop briefly
to consider how observance of safety precautions and
the use of safeguards protect you from injury. Consider
the complications that could be caused by your loss of
sight, or loss or mutilation of an arm or hand.
The following operating instructions and safety
precautions are applicable in general to all grinders and
specifically to the pedestal grinders.
— When starting a grinder, push the start button
and stand to one side for at least 1 minute while the
machine comes up to full speed. There is always a
possibility that a wheel may shatter when coming up to
— Never force work against a cold wheel. Apply
work gradually to give the wheel an opportunity to
warm. This will minimize the possibility of breakage.
— Handle wheels carefully. Before replacing a
wheel on a grinder, always sound the new wheel for
cracks. To sound a wheel, tap it lightly with a piece of
hard wood. A good wheel gives out a clear ringing
sound, and a cracked wheel gives out a dull “thud.”
Make sure that a fiber or rubber gasket is in place
between each side of the wheel and its retaining washer
(spindle wheel flange). Tighten the spindle nut just
enough to hold the wheel firmly. If the nut is tightened
too much, the clamping strain may damage the wheel.
— When selecting a replacement wheel, check to
be sure that the grinder rpm will not exceed the manufacturer’s recommended speed for the wheel.
— Read posted safety precautions before you start
to use a machine. In addition to refreshing your memory
about safe grinding practices, this gets your mind on the
job at hand.
— When grinding, always keep the work moving
across the face of the wheel. This will prevent grooves
from being worn into the face of the wheel.
— Keep all wheel guards tight and in place.
— Secure all loose clothing and remove rings or
other jewelry.
— Keep the spindle bearings well oiled.
— Inspect the grinding wheel, wheel guards, the
tool rest, and other safety devices to ensure they are in
good condition and positioned properly. Set the tool rest
so that it is within 1/8 inch of the wheel face and level
with the center of the wheel.
— Dress wheels frequently to keep them clean,
sharp, and true, but do not remove any more material
than necessary.
— Keep the tool rest adjusted so that it just clears
the wheel (never more than one-sixteenth inch) and is
at or just below the center line of the wheel. This will
prevent accidental jamming of the work between the
toolrest and the wheel.
— Use light pressure when you start grinding; too
much pressure on a cold wheel may cause failure.
— Grind only on the face or outer circumference
of a grinding wheel unless the wheel is specifically
designed for side grinding.
— Do not wear gloves when operating a pedestal
— If a lot of metal is to be removed, use the coarse
wheel to remove most of it.
— Use a gauge, template, or a sample for comparison, unless you are familiar with the exact finished
shape of the article you are grinding.
Grinding Wheels
A grinding wheel is made up of two basic
elements: (1) the abrasive grains and (2) the bending
agent. The abrasive grains may be compared to many
single-point tools embedded in a toolholder of
bonding agent. Each of these grains removes a very
small chip from the material as it makes contact on
each revolution of the grinding wheel.
An ideal cutting tool is one that will sharpen itself
when it becomes dull. This, in effect, is what happens
to the abrasive grains. As the individual grains become
dull, the pressure that is generated on them causes
them to fracture and present new sharp cutting edges
to the work. When the grains can fracture no more, the
pressure becomes too great and they are released from
the bond, allowing a new layer of sharp grains to be
presented to the work.
all manufacturers. The shapes are shown in crosssectional views. The specific job will dictate the shape
of wheel you should use.
SIZES AND SHAPES.—Grinding wheels come
in various sizes and shapes. The size of a grinding
wheel is given in terms of its diameter in inches, the
diameter of its spindle hole, and the width of its face.
Grinding wheels have too many shapes to list in this
manual, however, figure 5-59 shows those used most
often. The type numbers are standard and are used by
WHEEL MARKINGS AND COMPOSITION.—Grinding wheel markings are comprised of
six sections, each of which identifies a characteristic
of the wheel. The six sections are (1) type of abrasive,
(2) grain size, (3) bond grade, (4) structure, (5) type
of bond, (6) the manufacturer’s record symbol. Figure
5-60 shows the standard marking system and possible
Figure 5-59.—Grinding wheel shapes.
Figure 5-60.—Standard marking system for grinding wheels (except diamond).
variations that identify nearly all abrasives except
diamond. The following information breaks the marking down and explains each section. Follow the sections in the figure from left to right as you read an
explanation of each section in the following paragraphs. This information should be studied carefully
as it will be invaluable in making the proper wheel
selection for each grinding job you will attempt.
Grain Size.—The second section on the grinding
wheel marking is the grain size. Grain sizes range from
10 to 600. The size is determined by the size of mesh
of a sieve through which the grains can pass. Generally
speaking, grain size is rated as follows: coarse: 10
through 24; medium: 30 through 60; fine: 70 through
180; and very fine: 220 through 600. Fine grain wheels
are preferred for grinding hard materials, as they have
more cutting edges and will cut faster than coarse grain
wheels. Coarse grain wheels are generally preferred
for rapid metal removal on softer materials.
Type of Abrasive.—The first section on the
grinding wheel marking shows the type of abrasive.
There are two types of abrasives: natural and
manufactured. Natural abrasive, such as emery,
corundum, and diamond, are used only in honing
stones and in special types of grinding wheels. The
common manufactured abrasives are aluminum oxide
and silicon carbide. They have superior qualities and
are more economical than natural abrasives.
Aluminum oxide (designated by the letter A) is used
to grind steel and steel alloys, and for heavy duty work
such as cleaning up steel castings. Silicon carbide
(designated by the letter C), is harder but not as tough
as aluminum oxide. It is used mostly for grinding
nonferrous metals and carbide tools. The abrasive in
a grinding wheel makes up about 40 percent of the
Grade or Hardness.—Section three of the
grinding wheel marking is the grade or hardness of the
wheel. The grade is designated by a letter of the
alphabet and it runs from A to Z or soft to hard. The
grade of a grinding wheel is a measure of the bond’s
ability to retain the abrasive grains in the wheel. A soft
to hard grade does not mean that the bond or the
abrasive is soft or hard; it means that the wheel has
either a large amount of bond (hard grade) or a small
amount of bond (soft grade).
Figure 5-61 shows magnified portions of both
soft-grade and hard-grade wheels. You can see that a
part of the bond surrounds the abrasive grains, and the
remainder of the bond forms into posts that hold the
grains to the wheel and hold them apart from each
other. The wheel with the larger amount of bonding
material (hard grade) has thick bond posts and offers
great resistance to grinding pressures. The wheel with
the least amount of bond (soft grade) offers less
resistance to grinding pressures.
Structure. —The fourth section of the grinding
wheel marking is the structure. The structure is
designated by numbers from 1 to 15. The structure of
a grinding wheel refers to the open space between the
grains, as shown in figure 5-61. Grains that are very
closely spaced are said to be dense; when grains are
wider apart, they are said to be open. Open grain
wheels remove more metal faster than close-grain
wheels. Also, dense, or close-grain wheels, normally
produce a finer finish. Structure makes up about 20
percent of the grinding wheel.
Bond Type.—The fifth section on the grinding
wheel marking is the bond type. The bond makes up
the remaining 40 percent of the grinding wheel and is
one of the most important parts of the wheel. The bond
determines the strength of the wheel. The six basic
types of bonds are vitrified, silicate, rubber, resinoid,
shellac, and oxychloride. We will discuss each type in
the following paragraphs.
Figure 5-61.— How bond affects the grade of a wheel. Wheel
Manufacturer’s Record.—The sixth section of
the grinding wheel marking is the manufacturer’s
record. This may be a letter or number, or both. It is
used by the manufacturer to designate bond
modifications or wheel characteristics.
VITRIFIED bonded wheels are designated by the
letter V. They are not affected by oil, acid, or water.
Vitrified bonded wheels are strong and porous, and
rapid temperature changes have little or no effect on
them. Do not run vitrified wheels faster than 6,500
surface feet per minute (sfpm).
SILICATE bonded wheels are designated by the
letter S. Silicate bonded wheels are used mainly on
large, slow rpm machines where a cooler cutting action
is desired. Silicate bonded wheels are softer than vitrified wheels, and they release the grains more readily.
Like the vitrified bonded wheel, do not run this wheel
in excess of 6,500 sfpm.
RUBBER bonded wheels are designated by the
letter R. These wheels are strong and elastic and they
are used as thin cutoff wheels. These wheels are used
extensively for regulating wheels on centerless grinders. Rubber bonded wheels produce a high finish and
can be run at speeds up to 16,000 sfpm.
RESINOID bonded wheels are designated by the
letter B. These wheels are shock resistant and strong and
are used for rough grinding and cutoff wheels. Like
rubber bonded wheels, you can run these wheels at
speeds up to 16,000 sfpm.
SHELLAC bonded wheels are designated by the
letter E. These wheels give a high finish and have a cool
cutting action when used as cutoff wheels. Shellac
bonded wheels can be run at speeds up to 12,500 sfpm.
OXYCHLORIDE bonded wheels are designated
by the letter O. Do not run these wheels at speeds
greater than 6,500 sfpm.
You should select a grinding wheel that has the
proper abrasive, grain, grade, and bond for the job.
You should base your selection on such factors as the
physical properties of the material to be ground, the
amount of stock to be removed (depth of cut), the
wheel speed and work speed, and the finish required.
To grind carbon and alloy steel, high-speed steel,
cast alloys, and malleable iron, you probably should
use an aluminum oxide abrasive. A silicon carbide
abrasive is most suitable for grinding nonferrous
metals, nonmetallic materials, and cemented carbides.
Generally, you'll choose coarser-grain wheels to
grind softer and more ductile the materials. Also use
coarser-grain wheels to remove a large amount of
material (except on very hard materials). If a good
finish is required, a fine grain wheel should be used.
For soft materials, small depth of cut, or high-work
speed, use a soft grade wheel. If the machine you are
using is worn, you may need to use a harder grade
wheel to offset the effects of that wear. You also can
use a harder grade wheel if you use a coolant with it.
Table 5-3 lists recommended grinding wheels for
Table 5-3.—Recommendations for Selecting Grinding Wheels
various operations. However, before you perform
these operations, you should be able to install and
dress the wheels properly, whenever required.
pedestal grinder must be properly installed; otherwise,
it will not operate properly and accidents may occur.
Before you install a wheel, inspect it for visible defects
and “sound” it by tapping lightly with a piece of hard
wood to determine if it has invisible cracks. A good
wheel will give out a clear ringing sound when tapped.
If you hear a dull thud, the wheel is cracked and should
not be used. When installing the wheel on the grinding
machine, you should always refer to the technical
manual to ensure that the wheel is correctly installed
and tightened.
Figure 5-62.—Using a grinding wheel dresser.
Figure 5-63.—Sensitive drill press.
Grinding wheels, like other cutting tools, require
frequent reconditioning of cutting surfaces to perform
efficiently. Dressing is the term used to describe the
process of cleaning the periphery of grinding wheels.
This cleaning breaks away dull abrasive grains and
smooths the surface so that there are no grooves.
Truing is the term used to describe the removal of
material from the cutting face of the wheel so that the
resultant surface runs absolutely true to some other
surface such as the grinding wheel shaft.
machines and the holding devices used make them
unsuitable for heavy work.
The radial drill press (fig. 5-64) has a movable
spindle that can be adjusted to the work. This machine
is especially useful when the workpiece is large,
bulky, or heavy, or when you need to drill many holes
with one setup, because the work does not have to be
readjusted for each hole. The arm and spindle are
designed so that the drill can be positioned easily over
the layout of the workpiece.
Before operating any drill press, do a visual
inspection to be certain that all parts are in the proper
place, secure, and in good operating condition. Check
all assemblies, such as the motor, head, pulleys, and
bench for loose mountings. Check the V-belt and
adjust it as necessary according to the manufacturer’s
technical manual. Make sure the electrical cord is
securely connected and that the insulation is not
damaged, chafed, or cracked.
The wheel dresser, shown in figure 5-62, is used
for dressing grinding wheels on pedestal grinders. To
dress a wheel with this tool, start the grinder and let it
come up to speed. Set the wheel dresser on the rest as
shown in figure 5-62 and bring it in firm contact with
the wheel. Move the wheel dresser back and forth
across the face of the wheel until the surface is clean
and approximately square with the sides of the wheel.
Several things can get a grinding wheel out of
balance. For instance, it may be out of roundness, and
you can usually correct this problem by dressing the
wheel. Or, it may get out of balance if part of the wheel
is immersed in coolant. If this happens, remove and
replace the wheel. If the wheel gets out of balance
axially, it probably will not affect the efficiency of the
wheel. To correct axial unbalance, simply remove the
wheel and clean the shaft spindle, the spindle hole, and
While the drill press is operating, be alert for any
sounds that signal trouble, such as squeaks or unusual
noises. Report any unusual or unsatisfactory
performance of the drill press to the petty officer in
charge of the shop.
Each time a wheel is dressed, you should check
the clearance between the tool rest and the wheel.
Reestablish the clearance at not more than 1/8 inch, as
required. To preclude possible injury, make all
adjustments with the machine secured.
There are many sizes and styles of drilling
machines or drill presses, each designed for a
particular type of work. Only the sensitive drill press
and the radial drill press will be covered in this section.
One type of upright drill press is the sensitive drill
press (fig. 5-63). It is used to drill small holes in work
under conditions that make it necessary for the
operator to “feel” what the cutting tool is doing. The
tool is fed into the work by a very simple device-a
lever, a pinion and shaft, and a rack that engages the
pinion. These drills are nearly always belt-driven
because the vibrations caused by gearing will reduce
their sensitivity. The high-speed range of these
Figure 5-64.—Radial drill press.
You must use a cutting oil when drilling steel or
wrought iron. Cast iron, aluminum, brass, and other
metals may be drilled dry at high drilling speeds.
However, you should use some medium to cool these
metals. This will reduce the chances of overheating the
drill bit and loss of the cutting edge. Compressed air
may be used for cast iron; oleic acid for copper;
sulphurized mineral oil for Monel; and water, lard, or
soluble oil and soda water for ferrous metals. (Soda
water reduces heat, overcomes rust, and improves the
System (PMS), described in Military Requirements
for Petty Officer Third Class, NAVEDTRA 12044.
PMS is minimum maintenance. If you feel more
maintenance is required, refer to the technical
publication and perform the necessary maintenance.
You are required to know the standard Navy
system for marking gas cylinders and to be able to
identify the cylinder valves and cylinders of various
gases. You should be familiar with the construction,
design, and size of these cylinders. You should also
know how to handle and stow gas cylinders in a safe
and proper manner. This section will give you a few
of the important facts about gas cylinders and cylinder
valves. Additional information concerning compressed gases can be found in MIL-STD-101, Color
Codes for Pipelines and for Compressed Gas
After operating a drill press, wipe off all dirt, oil,
and metal particles. Inspect the V-belt to make sure no
metal chips are imbedded in the driving surfaces.
The machines in your shop depend upon you for
their care and maintenance. To keep your machines
operating properly, you should perform PMS
routinely. Preventive maintenance should be
performed according to the Planned Maintenance
Figure 5-65.—Cutaway view of compressed gas cylinders: (A) Oxygen cylinder; (B) acetylene cylinder.
dissolved in acetone, and are assigned Navy serial
numbers on the volume basis. In other words, gases in
the liquid state are measured by weight, and those in
the gaseous state are measured by volume. Acetylene,
though dissolved in a liquid, is measured as a gas by
Gas cylinders are made of high-quality steel.
High-pressure gases, such as oxygen, hydrogen,
nitrogen, and compressed air are stored in cylinders of
seamless construction. Only nonshatterable
high-pressure gas cylinders may be used by ships or
activities operating outside the continental United
States. Cylinders for low-pressure gases, such as
acetylene, may be welded or brazed. All cylinders are
carefully tested, either at the factory or a designated
processing station, at pressures above the maximum
permissible charging pressure.
Since 1 August 1944, Navy serial numbers have a
designated letter placed before the numerals. This
letter shows the type of gas carried in the cylinder.
The lettering system assigns the following letters to
the gases:
The cylinders for most compressed gases are
shaped alike. However, cylinders for acetylene are
shorter and of a larger diameter, as shown in figure
All gas cylinders have safety devices either in the
valve, in the shoulder, in the bottom of the cylinder,
or in a combination of these places. A threaded valve
protection cap screws on the neck ring and protects the
E—Ethylene oxide
D—Carbon dioxide
J—Nitrous oxide
Gas cylinders are manufactured and maintained
according to the regulations of the Interstate
Commerce Commission (ICC). The ICC stipulates
that each cylinder be indented or stenciled with
prescribed identification markings. Cylinders larger
than 2 inches in diameter must be indented with serial
numbers. Therefore, cylinders exceeding 2 inches in
diameter, which are not assigned Navy serial numbers,
require manufacturer’s serial numbers. No more than
500 cylinders are allowed in each lot manufactured.
Requirements for ICC 8 (acetylene) and ICC 9
(aerosol dispenser) cylinders are exceptions to this
requirement. ICC 8 cylinders of all sizes require serial
numbers and ICC 9 cylinders of all sizes are assigned
lot numbers. However, an unlimited number per lot is
P—Liquefied petroleum gas (propane, butane, and
so on)
S—Sulfur dioxide
R—Methyl chloride
Z—Compressed air
L—Ethyl chloride
NO—Nitrogen dioxide
In addition to markings required by the ICC, gas
cylinders used by all three services—Navy, Army, and
Air Force —have certain standard identifying
features. So much injury and damage can be, and has
been, caused by mistaking one gas cylinder for
another. Therefore, a national program has been
established to make it almost impossible to confuse
cylinders. The identifying features used by the Armed
Forces in this program consist of using a color code
for painting the cylinders, stenciling the name of the
Navy-owned compressed-gas cylinders are
indented with figures and letters. In addition to the
identifications required by ICC regulations,
Navy-owned cylinders for gases in the liquid state
with a water capacity in excess of 15 pounds, or gases
in the gaseous state with a volume in excess of 658
cubic inches, are identified by an indented Navy serial
number. This number is preceded and followed by the
letters USN. Acetylene cylinders contain acetylene
Shatterproof cylinders are stenciled in two
locations with the phrase “Non-Shat” lengthwise and
90° from the titles. Letters must be either black or
white, and approximately 1 inch in size.
gas along two sides of the cylinder, and placing two
identifying symbols (decals) on the shoulder of each
cylinder. The gas cylinders must be painted as shown
in figure 5-66, and the arrangement of colors will
appear as shown in table 5-4.
Color Codes for Cylinders
If the color of the cylinders reduces the
effectiveness of the ship's camouflage scheme, canvas
covers painted with the camouflage colors should be
placed over the cylinders. Do not paint the cylinders
with camouflage paint.
Color coding is mandatory for compressed-gas
cylinders. Identifying colors are assigned by the
Standardization Division, Office of the Assistant
Secretary of Defense (Supply and Logistics).
Figure 5-66.—Location of color codes on gas cylinders.
Table 5-4.—Cylinder Color Code
Contents of cylinder
Medical anesthetic gases:
Cyclopropane. . . . . . . . . . . . . . . . . . . . . . . . . . .
Ethylene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Nitrous oxide . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel gases:
Acetylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hydrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manufactured gases. . . . . . . . . . . . . . . . . . . . . .
Petroleum (liquefied & nonliquefied) . . . . . . . . .
Industrial gases:
Butadiene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ethylene oxide . . . . . . . . . . . . . . . . . . . . . . . . . .
Ethyl chloride . . . . . . . . . . . . . . . . . . . . . . . . . . .
Propylene. . . . . . . . . . . . . . . . . . . . . . . . . .
Vinyl chloride . . . . . . . . . . . . . . . . . . . . . . . . . . .
Vinyl methyl ether. . . . . . . . . . . . . . . . . . . . . . . .
Aerosol insecticide. . . . . . . . . . . . . . . . . . . . . . .
Toxics and poisonous materials:
Carbon monoxide. . . . . . . . . . . . . . . . . . . . . . . .
Hydrogen sulfide . . . . . . . . . . . . . . . . . . . . . . . .
Methyl bromide. . . . . . . . . . . . . . . . . . . . . . . . . .
Boron trifluoride . . . . . . . . . . . . . . . . . . . . . . . . .
Chlorine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hydrogen chloride . . . . . . . . . . . . . . . . . . . . . . .
Phosgene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sulfur dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ammonia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Freons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Methyl chloride. . . . . . . . . . . . . . . . . . . . . . . . . .
Oxidizing gases:
Oxygen, aviator's . . . . . . . . . . . . . . . . . . . . . . . .
Air, oil pumped . . . . . . . . . . . . . . . . . . . . . . . . . .
Air, water pumped . . . . . . . . . . . . . . . . . . . . . . .
Helium-oxygen. . . . . . . . . . . . . . . . . . . . . . . . . .
Oxygen-carbon dioxide . . . . . . . . . . . . . . . . . . .
Inert gases:
Argon, oil pumped . . . . . . . . . . . . . . . . . . . . . . .
Argon, water pumped. . . . . . . . . . . . . . . . . . . . .
Carbon dioxide. . . . . . . . . . . . . . . . . . . . . . . . . .
Helium, oil pumped. . . . . . . . . . . . . . . . . . . . . . .
Helium, oil free . . . . . . . . . . . . . . . . . . . . . . . . . .
Nitrogen, oil pumped . . . . . . . . . . . . . . . . . . . . .
Nitrogen, water pumped. . . . . . . . . . . . . . . . . . .
Fire-fighting gases:
Carbon dioxide. . . . . . . . . . . . . . . . . . . . . . . . . .
Methyl bromide. . . . . . . . . . . . . . . . . . . . . . . . . .
Location of cylinder markings
Top A
B and B
B and C
Buff (tan)
Buff (tan)
Buff (tan)
Buff (tan)
Buff (tan)
Buff (tan)
Buff (tan)
Buff (tan)
Buff (tan)
Cylinders that have a background color of yellow,
orange, or buff have the title stenciled in black.
Cylinders that have a background color of red, brown,
black, blue, gray, or green have the title stenciled in
white. Figure 5-67 shows how cylinders are identified
by the overall painted color code and by the stenciled
name of the gas.
As a further identification measure, two decalcomanias (pronounced de-kel-ko-main-e-ah, or abbreviated as decals), are applied to the shoulder of each
cylinder. The decals show the name of the gas and the
precautions for its handling and use. The decals are
available from general stores for each gas used in the
ICC regulations require that all gas cylinders,
except acetylene cylinders, be retested every 5 years.
Cylinders that are due for retesting are not to be
charged and shipped until such retests have been
properly made. However, cylinders that have been
charged before the expiration of their retest period
may be shipped and used until empty. They will then
be turned in for retesting. The dates of retests are
permanently and plainly marked by the stamping on
the shoulder of the cylinder, directly opposite the ICC
and Navy serial numbers. The stamping, for example
4-88, means that the last test was performed in April
The 5-year tests are performed by naval activities
and civilian agencies under regulations of the ICC.
Personnel aboard naval ships are not authorized to
perform such tests. Empty cylinders with expired test
periods should be returned to the nearest naval supply
depot or cylinder testing activity, and marked “For
You must always remember ALL compressed
gases are hazardous. Many detailed precautions could
be set down with regard to the handling and stowing
of these gases. The more important ones are
summarized in this section.
The term stowage as used in the following
paragraphs refers to articles under the cognizance of
the supply officer, in general stores, to be drawn on
for the ship’s own use, or articles of cargo being
Figure 5-67.—Identifying color patterns for gas cylinders.
transported. It does not refer to cylinders that have
been removed from stores or from cargo and
transferred to the shops or other locations for use.
— Metal strap clamps provided for retaining the
tops of the cylinders in place. Chains are not to be used
as retainers since they normally are a little slack; the
cylinders can shift and cause an accident.
The term ready service refers to cylinders or other
articles that have been transferred from stores and are
actually located in a shop or near a place where they
are to be used. It is not necessary that the articles be
in actual use, but they must be ready for use.
Stowage of Compressed Gases
In general, weather-deck stowage will be provided
for flammable and explosive gases. However, in
specific cases, below-deck stowage is approved;
depending on the particular type, mission, and
arrangement of the ship. In such cases, these approved
locations are shown on the ship’s plans.
Handling Cylinders
Cylinders that contain flammable and/or
explosive gases must be handled with extreme care.
Every effort should be made to avoid dropping them
or allowing them to strike too hard against each other
or any other object. Take every precaution to prevent
bumping or striking the discharge valves.
Compressed gases aboard all ships, except cargo
ships, should be stowed only in compartments
designated by NAVSEA, as shown in applicable plans
for the ship. In such cases, the following precautions
must be observed:
When cylinders are being handled, the cylinder
valve outlet cap and the cylinder valve protecting cap
must be in place. Unless ready-service cylinders are
secured in special portable racks, regulators must be
removed and caps replaced before the cylinders are
moved to a new location. Even then, it is best to
remove the regulators and replace the caps for safety.
Take necessary steps to keep the maximum
temperature of the stowage compartment below 130°F.
When provisions are made for mechanical
ventilation, operate this ventilation according
to the damage control classification assigned.
The classification for closures of this system
are either “Z, ” “W,” or “W.”
Be very careful when loading or transferring
cylinders, especially when using a crane or derrick.
The cylinders must be secured in a cradle, suitable
platform, rack, or special container such as a sandbag.
Electromagnets must never be used. A cylinder moved
by hand should be tilted slightly and rolled on its
bottom edge, without dragging or sliding. Hooks or
lines through the valve protection cap must not be used
for hoisting cylinders. Cylinders frozen to the deck, or
otherwise fixed, must not be pried loose with crowbars
or similar tools.
Do not install portable electric wiring and
equipment in compartments designated for
the stowage of flammable or explosive gases.
Keep flammable materials, especially grease
and oil, out of the stowage space.
Securely fasten each cylinder individually, in
the vertical position (valve end up), by metal
collars. Other arrangements are approved for
cargo ships fitted especially for cylinder transport.
When gas cylinders are transported on a hand
truck, they must be held securely in position. The truck
should be fastened to a bulkhead or stanchion as soon
as the destination is reached. The truck should be
constructed as follows:
Stow oxygen and chlorine in compartments
separate from flammable gases. Inert or nonflammable gases may be stowed in any compartment designated for compressed gas
— Frame sufficiently rigid to permit handling
with tackle.
— Grips or handles ending in a vertical line with
the aft side of the wheels. (This facilitates fastening to
a bulkhead.)
Ventilate compartments containing compressed gases for 15 minutes before entry in
the event that ventilation has been closed
down. A suitable sign to this effect should be
posted on the outside of the access door.
— Platform fitted with sides to prevent the cylinders from sliding off.
When compressed gas is stowed on the weather
deck, the following additional precautions must be
Stow cylinders attached to NAVSEA-approved damage control equipment below
decks in repair lockers. Spare cylinders used
for this purpose may be stowed in the same
Do not stow oxygen and chlorine cylinders
close to the fuel-gas cylinders. Normal practice is to stow gas cylinders on one side of the
ship and to stow oxygen and chlorine cylinders on the other side.
Remove welding units from the designated
stowage location to perform work at some
remote location in the ship. Return these units
to the designated stowage location immediately after you complete your work. Attend to
the equipment at all times while it is away
from its regular stowage.
Stow cylinders containing compressed gases
for the greatest possible protection. During the
winter, protect cylinder valves against the accumulation of snow and ice. Use warm water
(not boiling) to thaw ice accumulations in
cylinder valve caps and outlets. Boiling water
may melt the fusible plugs. During the summer, screen cylinders from the direct rays of
the sun.
Post a card showing the following warning at
the designated stowage location of each unit:
Make every effort to prevent corrosion of
threaded connections of cylinders that are
stowed for extended periods of time. The use
of grease, lubricants, or flammable corrosion
inhibitors on oxygen cylinders is NOT permitted. Oil or grease in the presence of oxygen
under pressure will ignite violently.
Attach a card showing the following statement
to each unit:
The stowage area should be as far away as
practical from navigation stations, fire control
stations, and gun mounts.
Cylinders in actual use, and those attached to
welding, fire fighting, medical, refrigeration, or
similar apparatus, ready for use, are permitted below
decks outside of the stowage compartment.
The following special precautions must be taken
with oxygen and fuel-gas cylinders for welding:
See NSTM, chapters 550 and 074, volume 3, for
detailed precautions.
Ready-Service Storage Rules
The number of cylinders of gas needed to
equip each authorized gas cutting and welding
position may be installed in shops. The number of authorized positions will be determined
from either a NAVSEA-approved plan or the
machinery specifications for the shop concerned.
Empty cylinders should be delivered to the nearest
naval supply depot. Valves should be closed and under
some positive pressure, except where the design of the
valve does not permit closing, as is the case with fire
extinguishers. The pressure is necessary to prevent
condensation of atmospheric moisture on the internal
walls. In the case of acetylene cylinders, the pressure
prevents loss of the solvent (acetone) and/or entry of
Securely fasten cylinders in a rack. The rack
must be securely fastened to the bulkhead, and
must not allow any vertical movement of cylinders.
air, if the cylinders cool considerably below the
temperature at which they were discharged.
Sometimes, cylinders used for aviator’s breathing
oxygen, dry nitrogen, argon, or dry air are found to
have open valves and/or a positive internal pressure of
less than 25 psi. These cylinders should be tagged with
the explanation that they must be dried before they are
Navy standard gas cylinder valves are of two basic
designs: packed valves and diaphragm-type packless
Packed valves require a packing material around
the valve stem to prevent leakage. The valve stem is
packed to prevent gas from leaking out around the
stem when the valve is open. MIL-V-2 covers the
authorized packing material for gas cylinder valves.
Figure 5-68.—Oxygen cylinder gas valves: (A) external view of
one type of valve, with related safety and outlet connection
caps; (B) cutaway view of the same valve, showing
diaphragms to prevent gas leakage when the valve is
opened; (C) cutaway view of another type of valve, with
asbestos packing to prevent gas leakage when the valve is
Packless valves are sealed against leakage around
the valve stem by flexible metallic diaphragms
securely clamped to the valve bonnets. The basic
packless design may be classified into two types:
nonbackseating and backseating. The nonbackseating
type is designed so that the metallic sealing
diaphragms may not be replaced under pressure. In the
backseating type the metallic diaphragms may be
replaced without undue hazard or loss of contained
gases if the outlet cap is in place and secure.
Diaphragms in packless valves should be replaced
only by activities carrying spare diaphragms
specifically designed for the valves in need of
gas flows through a threaded male cylinder connection
into the valve body and past the valve outlet
connection into the pressure regulator. (Pressure
regulators reduce the pressure of compressed gases
from the cylinder pressure to the desired working
These diaphragms are made from materials
selected for service at varying high pressures. In
addition, they are often designed only for use with
valves built by a given manufacturer and for a specific
The Navy gas valve program (and concerned
civilian agencies) provides noninterchangeable valve
outlets and connections for different gases to prevent
the use of the wrong gas at any time.
Construction and Identification of Valves
Valves designed to control the flow of compressed
gases are forged of brass, bronze, or steel, and are
made in various shapes and sizes. Figures 5-68 and
5-69 show typical gas cylinder valves. The valves are
opened and closed with either hand-operated or
wrench-operated spindles. When the valves are open,
Figure 5-69.—Cutaway view of an acetylene cylinder valve
showing asbestos packing.
Pressures ranging from 2,600 to 3,000 psi will rupture
the safety disk and allow the gas in the cylinder to vent
to the atmosphere. This type of safety device is used in
carbon dioxide service.
pressure. All regulators are marked with the name of
the gas for which they are intended.)
To prevent leakage of gas above the valve stem
when the valve is opened, each valve is equipped with
asbestos, leather, rubber packing, or metal
diaphragms. Most valves have safety devices. (The
safety devices for acetylene and ammonia are in the
cylinders rather than in the valves.) These safety
devices consist of fusible metal plugs, rupture disks,
or both. Spring-loaded safety devices are used for
some gases. If heat causes too much pressure, the fuse
plugs melt and the disks burst, releasing the contents
of the cylinder. Acetylene valves have screens in the
cylinder connections; other valves do not.
DISK—Backed safety caps with rupture disks are
essentially the same as those described in paragraph 3.
However, the breakable disk is supported by fusible
metal contained in the safety cap thus blocking off
escape ports. This cap works when the cylinder, valve,
and therefore the fusible metal are heated above the
melting temperature. When the pressure within the
cylinder reaches 2,600 to 3,000 psi, the breakable disk
ruptures and reduces the pressure. This type of device
is used commonly on air, argon, helium, hydrogen,
nitrogen, and oxygen valves.
Valves manufactured according to the latest
military specifications have the name of the gas, or
service for which they are designed. indented on at
least one of the flats on the sides of the valves. Valves
must be used only for the gases or fluids indicated.
Otherwise, personnel may be injured or the equipment
may be damaged.
Lea king Valves
Cylinders with leaking or defective valves should
be tagged as such and turned in to the nearest naval
supply depot for overhaul.
Safety Devices for Valves
Safety Precautions
Military specifications and ICC regulations
require that valves designed for certain services be
fitted with safety devices. These devices guard against
a buildup of hazardous pressures caused by heat. This
can easily happen with CO2 cylinders used for fire
fighting in fire rooms and engine rooms. Pressure can
also build up from overcharging or similar causes.
These safety devices may be divided into four general
categories based on functional design as follows:
Cylinders, regulators, hoses, and torches are
important parts of the shop equipment for heating,
welding, and cutting. Learn and follow these safety
rules for this type of equipment:
Never fill a cylinder with a gas other than the
gas for which it is specifically designated.
Never remove or change the decals.
1. FUSIBLE PLUGS—A fusible plug may be
described as a threaded hex-head plug with a center
filled with fusible metal. When the cylinder is
overheated, the fusible metal melts and permits the gas
to escape. This type of device is used on chlorine, freon,
acetylene, and such gases.
Never return an empty cylinder without making sure that valves are closed and that protective caps are in place.
Never drop the cylinders or let them strike
against each other.
These devices usually function as “pop” valves that
open to release excess pressure when pressure in the
cylinder overcomes spring tension. Devices of this sort
are used on liquefied petroleum gas valves. They
operate generally at about 150 percent of the cylinder’s
ICC-approved pressure.
Never hammer or strike the valve wheel to
open or close the valve. Use only the wrenches
or tools approved for that purpose.
RUPTURE DISK—This safety device is essentially a
safety cap that covers a safety port in the valve. The cap
retains a breakable disk firmly over the safety port.
Never use a cylinder that IS improperly
marked; that is, where the paint color doesn’t
agree with the information on the decal.
Never use cylinders as rollers or supports.
If valve outlets are iced, use only warm water
to free them. Never use hot or boiling water.
Never use a lifting magnet or a sling to raise
or handle a cylinder.
Be careful not to mix full and empty cylinders
in a stowage rack.
Never tamper with safety devices on the
valves or cylinders.
Never store oxygen and acetylene cylinders in
the same immediate area.
Be especially careful that you never strike an
arc on gas cylinders or sealed metal cylinders
of any kind.
Acetylene and low-pressure fuel-gas cylinders, which have been stowed in a horizontal
position, must be placed in a vertical position
for at least 2 hours before you use them. This
will allow the porous filler material inside the
cylinder to settle.
This chapter gave you a brief introduction to the
handtools, power tools, and installed equipment used
by HTs. The importance of caring for these tools
properly cannot be stressed enough. Learn to use them
correctly and protect them from loss or damage. These
tools will determine how well you perform your job.
Now you also have an understanding of the
operations and safety precautions of portable hand and
power tools, pneumatic tools, grinders, drilling
machines, bandsaws, power hacksaws, and threadcutting tools. However, it would be to your advantage
to read the manufacturers’ operating manuals for all
of shop tools and equipment. You should also review
the section on compressed-gas cylinders and the safety
precautions involved with them. You will find that you
will work with some aspect of compressed-gas
cylinders almost every day.
Upon completion of this chapter; you will be able to do the following:
Explain the concepts of stress and strain in metals.
Describe the different properties of metals.
Identify the two major classes of metals.
Describe the different types offerrous and nonferrous metals.
Identify different metals by color markings, surface appearance, and identification tests.
elements. The elements that are used as alloying substances are usually metals or metalloids. By combining
metals and metalloids, it is possible to develop alloys
that have the particular properties required for a given
Table 6-1 lists some common metals and
metalloids and gives the chemical symbol that is used
to identify each element.
As an HT, you will be working with many different
types of metals and alloys. The more knowledge you
have of metals and alloys, the better you will be able to
perform your repair and maintenance duties. You
should have some accurate means of identifying metals.
To intelligently solve welding problems, you should
also have a good understanding of the internal structure
of metals, and the effects that welding (heat input) has
on metals. This chapter will start you on your way by
giving you a basic understanding of metallurgy.
Can you define a metal? Chemical elements are
considered to be metals if they are lustrous, hard, good
conductors of heat and electricity, malleable, ductile,
and heavy. Some metals are heavier than others; some
are more malleable than others; and some are better
conductors of heat and electricity. These properties are
known as “metallic properties,” and chemical elements
that possess these properties to some degree are called
metals. Chemical elements that do not possess these
properties are called nonmetals. Oxygen, hydrogen,
chlorine, and iodine are examples of nonmetallic
chemical elements.
Chemical elements that behave sometimes like
metals and sometimes like nonmetals are often called
metalloids. Carbon, silicon, and boron are examples of
An alloy may be defined as a substance that has
metallic properties and is composed of two or more
Table 6-1.—Symbols of Common Metals and Metalloids
CARBON STEEL is an alloy of iron and controlled amounts of carbon. ALLOY STEEL is a combination of carbon steel and controlled amounts of other
desirable metal elements.
When external force is applied to any solid
material, the material is subjected to stress. Many of
the properties of metals can best be understood in
terms of the manner in which they react to stress.
Therefore, before considering the properties of metals
and alloys, let us examine the concepts of stress and
The percentage of carbon content determines the
type of carbon steel. For example, wrought iron has
0.003 percent carbon, meaning three thousandths of
one percent. Low-carbon steel contains less than 0.30
percent carbon. Medium-carbon steel varies between
0.30 and 0.55 percent carbon content. High-carbon
steel contains approximately 0.55 to 0.80 percent
carbon, and very-high-carbon steel contains between
0.80 and 1.70 percent carbon. Cast iron contains 1.8
to 4 percent carbon.
Load, which is usually measured in pounds, is the
external force applied to a material. When the load is
applied, reaction forces to the load occur throughout
the material. The reaction forces are stresses. Why do
these forces occur when a load is applied to a material?
Newton's third law of motion states that “to every
force or action, there is an equal and opposite
reaction.” Stress, therefore, is the “equal and
opposite” reaction to the externally applied load. It is
defined as the force per unit area resisting the load.
Unit area is important. The unit area may be stated as
a square inch, a square foot, or any other predetermined amount of area that is used to figure the
amount of stress that the material will be subjected to.
When the load is applied, it is distributed equally
throughout the cross section of the material. For
example, suppose two round metal rods with
cross-sectional areas of 1 square inch and 2 square
inches are each supporting a 2000-pound weight. The
load or external force is the same on both, but since
the cross-sectional areas are different and the load is
distributed equally over the cross-sectional areas, the
stresses in the two rods are also different.
Carbon generally combines with the iron to form
CEMENTITE, a very hard, brittle substance.
Cementite is also known as IRON CARBIDE. This
action means that as the carbon content of the steel
increases, the hardness, the strength, and the
brittleness of the steel also tend to increase.
Various heat treatments are used to enable steel to
retain its strength at the higher carbon contents, and
yet not have the extreme brittleness usually associated
with high carbon steels. Also, certain other substances,
such as nickel, chromium, manganese, vanadium, and
other alloying metals, may be added to steel to
improve certain physical properties.
A welder must also have an understanding of the
impurities occasionally found in metals and their effect upon the weldability of the metal. Two of the
detrimental impurities sometimes found in steels are
phosphorus and sulphur. Their presence in steel is due
to their presence in the ore, or to the method of manufacture. Both of these impurities are detrimental to the
welding qualities of steel. Therefore, during the manufacturing process, extreme care must always be taken
to keep the impurities at a minimum (0.05 percent or
less). Sulphur improves the machining qualities of
steel, but it is detrimental to its hot forming properties.
You can see from the example that the stress is
equal to the load divided by the cross-sectional area.
That is, equal portions of the load are distributed
equally over the cross-sectional area. Stress is usually
measured in pounds (for load) per square inch (for
area). Conversely, the load can be determined by
multiplying the stress by the cross-sectional area.
Strain is the deformation or change in shape
caused by the load. Some strain always occurs as a
reaction to a load. The amount of strain depends on
the magnitude and duration of the stress caused by the
load. It also depends on the type and condition of the
material. Strain is measured in inches per inch or in
percentage. Thus, when a load is applied to a bar in
tension, the bar will elongate (be strained) some fraction of an inch for each inch of bar (the strain will be
the same in each inch of bar). If strain is being measured in percentage, the bar will be elongated a certain
percentage; that is, the total length of the bar will be
During a welding operation, sulphur or
phosphorus tends to form gas in the molten metal. The
resulting gas pockets in the welds cause brittleness.
Another impurity is dirt or slag (iron oxide). The dirt
or slag is imbedded in the metal during rolling. Some
of the dirt may come from the by-products of the
process of refining the metal. These impurities may
also produce blow holes in the weld and reduce the
physical properties of the metal in general.
increased a certain amount, which will be a percentage of the original length.
Stress occurs because molecular forces within the
material resist the change of shape that an applied
load tends to produce. In other words, stress results
from the resistance of the molecules to being shifted
around, pulled apart, or squeezed together. Because
stress involves molecular forces, a piece of metal that
is subjected to a load develops an enormous number
of stresses, rather than just one stress. If you had more
than a very few molecules, you would have to draw
thousands or perhaps millions of arrows to indicate all
the molecular forces involved. We often speak of
stress as though it were one internal force, acting in
one direction; that is, the direction opposite to the
direction of the applied load. In other words, we consider the TOTAL EFFECT of all the molecular
stresses, rather than trying to consider each set of
molecular stresses separately.
Figure 6-1.—Tension forces and tension stresses.
The manner in which the load is applied determines the type of stress that will develop. Applied
forces are usually considered as being of three basic
kinds: tension (or tensile) forces, compression forces,
and shearing forces. The basic stresses, therefore, are
tension (or tensile) stresses, compression stresses, and
shearing stresses. Complex stresses such as bending
stresses and torsional stresses are combinations of two
or more of the basic stresses.
Tension stresses develop when a material is subjected to a pulling action. If, for example, a cable is
fastened to an overhead clamp and a weight is attached to the free end, tension stresses develop within
the cable. The tension stresses resist the tension forces
that tend to pull the cable apart. Figure 6-1 shows
tension forces and the resulting “equal and opposite”
tension stresses.
Figure 6-2.—Compression forces and compression stresses.
Compression stresses develop within a material to
oppose the forces that tend to compress or crush the
material. A column that supports an overhead weight
is said to be in compression, and the internal stresses
that develop within the column are compression
stresses. Figure 6-2 shows compression forces and
compression stresses.
Shearing stresses develop within a material when
opposite external forces are applied along parallel
lines in such a way as to tend to cut the material.
Shearing forces tend to separate material by sliding
part of the material in the opposite direction. The
action of a pair of scissors is an example of shear
forces and shear stresses. The scissors apply shear
forces, and the material being cut resists the shear
forces by its internal shear stresses. Forces tending to
produce shear in a rivet are illustrated in figure 6-3.
Shear stresses are not shown, since they are
considerably more complex than tension stresses and
compression stresses.
Torsional stresses develop in a material when
external forces are applied in such a way that they tend
to produce rotation. A ship’s shaft, for example,
rotates when the external applied forces are greater
than the internal torsional stresses developed in the
shaft. Torsional stress is primarily a special form of
shear stress, although it may also involve some
compression stress and some tension stress.
Bending stresses develop when a material is
subjected to external forces that tend to bend it. When
a load is applied to a beam, for example, as shown in
figure 6-4, the upper surface is in compression and the
lower surface is in tension. The NEUTRAL AXIS,
indicated by the broken line in figure 6-4, is neither in
compression nor in tension.
The atoms in all solid metals are arranged in some
definite geometric (or crystallographic) pattern. The
smallest grouping of atoms that has the complete
symmetrical arrangement of the crystal is called a unit
cell. The regular arrangement of these atoms is called
a space lattice. A unit cell is much too small to be seen.
When a great many unit cells are combined, however,
they form a visible crystal that has the same geometric
structure as the unit cell.
A number of different geometrical arrangements
of atoms are possible, but most metals have space
lattices that are basically shaped like cubes, tetragons,
or hexagons. Figure 6-5 shows the body-centered
cubic and face-centered cubic space lattices.
Figure 6-3.—Shearing forces applied to a rivet.
How do crystals form? When the metal is in the
liquid state, the atoms move freely and are not
arranged in any orderly fashion. When the metal
begins to cool, however, the atoms move more and
more slowly. When the freezing (solidifying)
temperature of the metal is reached, the atoms begin
to form unit cells of the type characteristic of the
particular metal. In this crystallization process, the
atoms give up energy in the form of heat. As this
energy flows from the metal, other atoms form around
each of the original unit cells in a definite pattern. This
definite and repeating pattern upon solidification is
called a space lattice. Eventually all of the metal is
changed from the liquid state, in which the atoms are
moving freely, to the solid state, in which the atoms
are arranged in a definite, orderly pattern. At this
point, we say that the metal has completely solidified
or frozen.
Figure 6-4.—Load applied to a beam.
If crystallization could proceed without any
interference, the result would be one large crystal with
the external form of the internal space lattice. As a
rule, however, the space lattices do not all line up
perfectly with each other; this means that the growth
of some crystals interferes with the growth of others.
Figure 6-5.—Crystal structure of iron. A. Body-centered cubic,
9-atom space lattice. B. Face-centered cubic, 14-atom space
have the typical shape of the space lattice, it is customary to call each visible unit a grain rather than a crystal.
The areas between adjacent grains are shown as grain
boundaries. The grain boundary material has somewhat
different properties than the actual grains or crystals;
this is partly because the space lattices are distorted at
the grain boundaries and partly because the process of
crystallization tends to push impurities out of the crystals and into the grain boundaries.
The term grain structure refers to the crystalline
structure of the metal, often with particular reference to
the shape and size of the grains. Figure 6-6 illustrates
several types of gram structure, as seen under a microscope. The size of the grains depends upon a number of
factors, including the nature of the metal, the temperature to which it is heated, the length of time it is held at
a specified temperature, and the rate at which it is cooled
from a liquid to the solid state. In general, the quicker a
metal solidifies, the smaller the grain will be. The size
of grain structure desired for any particular application
depends upon the purpose for which the metal is to be
In alloys, the internal structure may be in the form
of crystals of pure metals, solid solutions, intermetallic
compounds, mechanical mixtures, or some combination of these structures.
In a solid solution, the elements are completely
dissolved in each other, with the atoms of each
element fitting into and forming part of the space
lattice of the other element. Figure 6-7 illustrates two
In other words, space lattices that are not oriented in
approximately the same way cannot join each other.
As a result, the crystallization process usually results
in the growth of many small crystals rather than one
large one. In any given piece of solid metal, the size
of the crystals will vary. The larger ones are the result
of the combination of a great many space lattices that
happened to line up in such a way that they could join
each other.
Because the crystals interfere with each other as
they grow, a piece of metal in cross section may show
very few characteristic crystal shapes. Note, however,
that the metal is still considered crystalline even if the
crystalline forms are distorted. The crystals are there,
but they are not usually perfect in shape.
When a metal crystallizes in such a way that the
crystals are not perfectly formed and therefore do not
Figure 6-7.—Space lattices of two forms of solid solution. A.
Atoms of one element fit between atoms of another element.
B. Atoms of one element replace atoms of another element.
Figure 6-6.—Grain structure in metals.
One intermetallic compound of great importance
in ferrous alloys is known as IRON CARBON or
CEMENTITE. This is an extremely hard and brittle
compound that is formed by the combination of iron
(a metal) and carbon (a metalloid). The formula for
iron carbide or cementite is Fe3C. This formula shows
that three atoms of iron combine with one atom of
carbon to produce iron carbide, or cementite.
ways in which solid solutions may exist. The atoms of
one element may fit into the spaces between the atoms
of another element, as indicated in view A; or the
atoms of one element may replace the atoms of another
element in the space lattice, as indicated in view B.
A solid solution in a metal is similar to many
solutions you are familiar with; for example, water
dissolves salt. The result is a wet salty liquid. The taste
of the salt and the wetness of the water have not
changed. As you see, there has been no change of
individual properties. However, you cannot see or
distinguish which is water or which is salt. The loss of
individual identity is apparent. An example of a
familiar solid solution is Monel metal. You know from
experience that Monel is tough, and yet, soft and
plastic; the toughness of nickel and the plasticity of
copper have been combined in the form of a metallic
solid solution.
The structure of an alloy is described as being a
MECHANICAL MIXTURE when two or more
structural forms are mixed together but are still
separately distinguishable. A mechanical mixture of
an alloy is comparable, though on a smaller scale, to
the mixture of sand and gravel that may be seen in
One of the most important mechanical mixtures
that occurs in many steels is known as PEARLITE.
Pearlite, so called because it has a pearly luster when
seen under a microscope, is an intimate mechanical
mixture of ferrite and cementite in alternate plates or
layers. Ferrite is a solid solution, and cementite or iron
carbide is an intermetallic compound; in pearlite the
two are closely mixed to form a characteristic layered
The individual elements lose their identity in a
solid solution. A polished cross section of a material
that consisted of only one solid solution would show
all grains to be of the same nominal composition.
Ferrite and austenite are two solid solutions that
are important constituents of steel. Ferrite is the name
given to a solid solution of alpha iron and carbon.
Austenite is the term for a solid solution of gamma iron
and carbon. Carbon is only slightly soluble in alpha
iron but is quite soluble in gamma iron. Alpha iron at
room temperature can hold only about 0.007 percent
carbon in solid solution. At a temperature of 2065°F.
gamma iron can hold up to about 1.7 percent carbon
in solid solution.
Pearlite is formed when steel that contains just
about 0.85 percent carbon is heated to a certain
temperature and then cooled slowly. When the entire
structure of the alloy is in the form of pearlite, this
composition of plain carbon steel (0.85 percent
carbon) is often referred to as the eutectoid
composition, and the completely pearlitic structure is
called the EUTECTOID or the EUTECTOID
INTERMETALLIC COMPOUNDS are compounds formed between a metal and some other substance such as carbon or sulfur. There are many
ordinary compounds that we are familiar with in everyday life; common table salt is one. The two poisonous elements, sodium and chlorine, when combined,
form sodium chloride or common table salt. Salt does
not resemble either sodium or chlorine, either by identity or properties. When the two elements are combined chemically, a new and different substance is
created. Under certain conditions, intermetallic compounds form and a new substance with new properties
is created in very much the same manner, but on a
more complicated basis. Perhaps the most important
thing to remember about the intermetallic compounds
is the loss of identity and the change in properties. The
heat treater quite often utilizes the change in properties
offered by compound formations in metals.
The internal structure of an alloy may show
various combinations of pure metals, solid solutions,
intermetallic compounds, and mechanical mixtures.
Many of the combinations that are important in steels
and other alloys are the result of controlled heating and
cooling of the alloy; in other words, they are the result
of heat treatment. Figure 6-8 shows, very much
enlarged, a typical combination that occurs when plain
carbon steel containing less than 0.85 percent carbon
is heated to a certain temperature and then cooled
slowly. As may be seen, this combination consists of
the solid solution ferrite and the mechanical mixture
pearlite, each in crystal form, distributed throughout
the alloy. The relative proportions of ferrite and
pearlite in this combination depend largely upon the
carbon content of the alloy.
This combination contains no free crystals of
ferrite; instead, it consists of crystals of pearlite
surrounded by cementite at the grain boundaries.
As previously noted, a deformation or change of
shape (strain) occurs when a material is subjected to
external forces that cause stresses in the material. The
ability of a material to return to its original size and
shape after strain is the property known as elasticity.
All materials are elastic to some extent. It may
surprise you to learn that a piece of steel is more elastic
than a rubber band. The rubber band stretches more
than the steel since it is more easily strained, but the
steel returns more nearly to its original shape and size
and is, therefore, more truly elastic. Glass is also more
elastic than rubber.
A PHYSICAL PROPERTY is a characteristic of a
metal that may be observed or measured. The physical
properties of steel are affected by the following:
Carbon content
Addition of various alloying metals
The greatest stress that a material is capable of
withstanding without taking a permanent set (that is
without becoming permanently deformed) is known
as the ELASTIC LIMIT. Below the elastic limit, the
amount of strain is directly proportional to the amount
of stress and, therefore, to the amount of externally
applied force. Above the elastic limit, however, the
amount of deformation that results from an increase in
load is way out of proportion to the increase in load.
Heat treatment
The particular properties that we require of any
metal or alloy depend upon the use we will make of
the material. For example, an anchor chain must have
the property of toughness; a boiler tube must have high
tensile strength, the ability to conduct heat, and the
ability to resist deformation or creep at high
temperatures; an electric wire must be able to conduct
electricity; a knife blade must have the property of
hardness; a spring must be elastic; a saltwater piping
system must resist corrosion; and a piece of metal that
is to be drawn out into a wire must possess the property
known as ductility. The following sections deal with
some important properties of metals and alloys.
Strain may be axial, angular, or both, depending
upon the nature of the applied load and the stresses
that are developed within the material to withstand the
applied load. When the elastic limit is exceeded
through the application of an axial load, the material
will be permanently deformed either by
applied load is not axial (as in shear and torsion), the
resulting strain is angular and, if permanent
deformation results, the deformation is also angular.
As noted before, the amount of strain is proportional to the amount of stress up to (or almost up to) the
elastic limit. The ratio of stress to strain is, therefore, a
constant for each material. This constant, which is
called the MODULUS OF ELASTICITY, is obtained
by dividing the stress by the strain, which is the elongation caused by that stress. For example, suppose that a
certain material is so loaded that the internal stress
developed in tension is 30,000 psi and that with this
stress the material elongates or is strained 0.0015 inch
per inch. The modulus of elasticity (E) of this material
Stress (psi)
Elongation (inch per inch)
30,000 psi
= 0.0015 inch per inch
Figure 6-8.—Typical structure of steel containing less than
0.85 percent carbon.
= 20,000,000 psi
considerably below its ultimate strength in tension,
compression, or shear. For example, you can break a
thin rod with your hands after it has been bent back
and forth several times in the same place, although you
could not possibly cause an identical rod to fail in
tension, compression, or shear merely from force
applied by hand. This tendency of a material to fail
after repeated stressing at the same point is known as
The modulus of elasticity is frequently used to
determine the amount of elongation that will occur
when a given stress is developed in the material. For
this purpose, you divide the stress by the modulus of
elasticity to obtain the elongation (inch per inch) that
will occur.
Closely related to the elastic limit of a material is
the YIELD POINT. The yield point is the stress at
which deformation of the material first increases
markedly without any increase in the applied load. The
yield point is always somewhat above the elastic limit.
When the stresses developed in a material are greater
than the yield point (or, as it is sometimes called, the
yield strength), the material is permanently deformed.
Metal fatigue is the tendency for a metal to break
under the action of repeated cyclic stresses. Fatigue
may occur for values of cyclic stress considerably less
than the ultimate tensile strength of the material. This
phenomenon applies to certain fractures in metals that
are caused by repeated stresses of a low enough value
that a single application of the stress apparently does
nothing detrimental to the structure. When enough of
these seemingly harmless stresses are applied in a
cyclic manner, however, they bring about a small
Strength is the property that enables a material to
resist deformation. ULTIMATE STRENGTH is the
maximum stress that a material is capable of
withstanding in tension, compression, or shear. The
COMPRESSIVE STRENGTH of a metal is a measure
of how much squeezing force it can withstand before
it fails. The metal to be tested is mounted in a tensile
tester, but instead of pulling on the metal, a squeezing
(compression) force is applied. TENSILE
STRENGTH, or the ultimate strength of a material in
tension, is the term most frequently used to describe
the strength of a material. Tensile strength is the
ability of a metal to resist being pulled apart. This
property may be measured on a tensile testing
machine, which puts a stretching load on the metal.
Figure 6-9 illustrates the types of loads imposed on
Table 6-2 shows how the tensile strength,
elongation (explained below), and yield point are
affected by the carbon content of steel. As the carbon
content increases, the tensile strength and yield point
first increase then decrease.
Some materials are equally strong in compression,
tension, and shear. However, many materials show
marked differences. For example, cured portland
cement has an ultimate strength of 2,000 psi in
compression, but only 600 psi in tension. Carbon steel
has an ultimate strength of 56,000 psi in tension and
in compression, but an ultimate strength in shear of
only 62,000 psi. In dealing with ultimate strength,
therefore, the kind of loading (tension, compression,
or shear) should always be stated.
If a material is stressed repeatedly, in a cyclical
manner it will probably fail at a loading that is
Figure 6-9.—Types of stresses or loads imposed on structures:
compression, tension, shear, torsion, bending, and fatigue.
Table 6-2.—Approximate Physical Property Changes of Carbon Steel as the Carbon Content Changes
AlSl No.
Carbon Content in
Tensile Strength
Lbs/sq. in
Yield Point
Lbs/sq. in.
Elongation in
crack that grows with continued loadings until
complete fracture takes place.
that can absorb a lot of energy before breaking.
Toughness does not exist in metals that do not have
high tensile strength; however, metals that are both
strong and hard tend to have less toughness than
metals that are softer and have less tensile strength.
Since the small cracks may not be noticed, the
metal may fracture with a suddenness that can be
dangerous, as in fast-moving vehicles or high-speed
machinery. Special inspection techniques have been
developed to spot small cracks before the material
fails. Fatigue failures are due to the repeated
application of tensile stresses or shear stresses, which
tend to pull the material apart. However, a cycle that
consists of alternating equal stresses in tension and
compression, called a fully reversed cycle, is usually
used to obtain the endurance limits of a particular
Toughness is definitely related to the property of
plasticity; materials must be plastic in order to be
Materials that can withstand extensive permanent
deformation without breaking or rupturing are said to
be highly plastic. Note the use of the word permanent
in this statement; the term plastic deformation is used
to indicate a PERMANENT change of shape.
Modeling clay is an example of a highly plastic
material since it can be deformed extensively and
permanently without rupturing. Clay could scarcely
be called tough, however, even though it is highly
The property of hardness has been defined as the
ability of a material to resist penetration. Because
there are several methods of measuring hardness, the
hardness of a material is always specified in terms of
the particular test that has been used to measure this
To get a simple idea of the property of hardness,
consider lead and steel. You can scratch lead with a
pointed wooden stick, but you cannot scratch steel
with such a stick. Steel is harder than lead.
Plasticity is in some ways the opposite of
brittleness and in other ways the opposite of elasticity.
A material that is brittle will break without showing
deformation. Such a material is not very plastic. A
material that is highly elastic will return to its original
shape after strain; consequently, such a material does
not show a high degree of plasticity (below the elastic
limit for the substance). Most metals are elastic, rather
than plastic, up to the elastic limit; above the elastic
limit, they tend to have the property of plasticity.
Toughness is the property that enables a material
to withstand shock, to endure tensile stresses, and to
be deformed without breaking. Another way of
expressing this is to say that a tough material is one
Plasticity, like many other properties, is relative.
To some degree, all substances are plastic. Even glass,
slowly at or below room temperature (so slowly, in
fact, that years are required to complete a single creep
test), the importance of this type of plastic
deformation has not been recognized until fairly
recent. Creep-resisting steel is now used in most
modem naval ships for high-temperature piping.
which is usually considered to be a nonplastic
material, is plastic if an external force is applied to it
very slowly. If you want to demonstrate this to
yourself, take a sheet of glass and lay it in a horizontal
position in such a way that it is supported only at the
ends. Then put a weight in the middle of the glass.
After several days (or possibly weeks, depending upon
the kind of glass you use), you will be able to observe
a visible deformation of the glass.
The substance known as “Silly Putty” is an even
better example of the relative nature of the property of
plasticity. When you slowly press or mold “Silly
Putty,” it is more plastic than chewing gum; throw it
against the floor and it may either bounce like a rubber
ball or break into pieces; hit it sharply with a hammer,
and it will shatter almost like glass.
Brittleness is the opposite of ductility. A brittle
metal will fracture if it is bent or struck a sharp blow.
A brittle material is one that fractures before
exhibiting any noticeable permanent deformation.
Most cast iron is very brittle.
Before these properties are studied in detail, the
welder should have an understanding of the effect of
carbon on the properties of steel and a knowledge of
alloys in general.
Corrosion resistance is the property that enables a
material to resist entering into chemical combination
with other substances. A high degree of corrosion
resistance would be very desirable in all metals used
aboard ship. Most metals are easily corroded,
however, as shown by the fact that pure metals occur
only rarely in nature.
The properties known as ductility and malleability
are special cases of plasticity. Ductility is the property
that makes it possible for a material to be drawn out
into a thin wire or, in other words, it is the property
that enables the material to withstand extensive
permanent deformation from TENSION. Ductility is
the ability of a metal to be stretched. A very ductile
metal such as copper or aluminum may be pulled
through dies to form wire. Malleability is the property
that makes it possible for a material to be stamped,
hammered, or rolled into thin sheets; a malleable
material is one that can withstand extensive permanent
deformation from COMPRESSION.
The presence of impurities, or the presence of
alloying elements, may greatly alter the corrosion
resistance of a metal. For example, the zinc that is
known as “commercially pure” contains a small
amount of impurities; this grade of zinc corrodes about
10,000 times as fast as zinc that is chemically pure. On
the other hand, many alloys have been developed for
the particular purpose of increasing the corrosion
resistance of the material. For example, pure iron
would be entirely unsuitable for use in boilers because
it has very poor resistance to corrosion, particularly at
high temperatures; yet alloys composed primarily of
iron are used successfully for this service.
Most metals that exhibit one of these properties
also exhibit the other. However, this is not always true.
Lead, for example, is very malleable (it can be
permanently deformed in compression without
breaking), but it is not ductile (it cannot be
permanently deformed in tension to any great extent).
Although not strictly properties, in the sense of the
other properties we have discussed, weldability and
machinability are important practical considerations
in the fabrication or repair of any metal part.
Weldability refers to the relative ease with which a
metal may be welded. Machinability describes the
ease with which a metal may be turned, planed, milled,
or otherwise shaped in the machine shop. Some metals
are not easily machined because they are too hard.
Some soft metals are not easily machined because they
are too tough. Both weldability and machinability are
really based upon the combination of other properties
The term creep describes a special kind of plastic
deformation that occurs very slowly at high
temperatures when the material is under a constant
stress. It is interesting to note that this stress may be
considerably less than the yield point of the material
at room temperature. Because creep occurs very
producing malleable cast iron. White cast iron derived
its name from the bright silvery appearance it has
when fractured. White cast iron is hard, brittle, wear
resistant, and unmachinable, largely because the
carbon it contains is present as cementite.
of the material, rather than being properties
Gray cast iron always contains iron, carbon, and
silicon, and generally contains more carbon and
silicon than white cast iron. Carbon is always present
in the form of graphite flakes. In addition, gray cast
iron often contains appreciable amounts of nickel and
other alloying elements. Gray cast iron is of three
varieties: common, high strength, and alloy. All three
are machinable and have good damping capacity
(ability to absorb and dampen vibrations). The
common gray cast irons are quite soft; the others are
somewhat stronger, particularly the alloy gray cast
iron. All three are brittle because the carbon they
contain is largely present in graphite flakes, which act
as severe stress raisers. Whether a cast iron is gray or
white depends upon the cooling rate and carbon,
silicon, and nickel content.
Metals are divided into two major fields: ferrous
metals and nonferrous metals. Ferrous metals are
those that are composed primarily of iron. Nonferrous
metals are those that are composed primarily of some
element or elements other than iron. Nonferrous
metals or alloys sometimes contain a small amount of
iron as an alloying element or impurity.
Ferrous metals include all forms of iron and steel.
Ferrous metals are widely used in the construction of
Commercially pure iron is known as INGOT
IRON. This iron is 99.85 percent iron; carbon,
manganese, phosphorous, sulfur, and a trace of silicon
make up the remainder. The chemical composition of
this iron is very similar to the chemical composition
of the lowest carbon steel.
Malleable cast iron is made by heating white
castings to 1700°F for about 50 hours, followed by
slow cooling to room temperature. The castings are
packed in a neutral slag or scale during heating and
cooling. During the heating period, the cementite in
the structure tends to decompose into ferrite plus
temper carbon. Malleable cast iron is strong,
machinable, and ductile. The mechanical properties of
malleable cast iron compare favorably with those of
low-carbon steels. Malleable cast iron is a great deal
more ductile than either white or gray cast iron.
WROUGHT IRON was used extensively for
construction and even for machinery before steels
came into use. Wrought iron is a mixture of very pure
iron and silica slag. The slag gives wrought iron some
of its desirable properties—corrosion resistance,
weldability, and ductility, among others. Wrought
iron is still used for some piping systems on auxiliary
Nodular cast iron is produced in the same way as
gray cast iron, but with much closer control of
composition and with the aid of inoculating agents.
The molten iron is inoculated with an alloy that will
produce spherical graphite rather than flake graphite.
Nodular cast iron possesses the good machinability,
damping capacity, and castability of gray cast iron. Its
strength is comparable to alloy gray cast irons and cast
carbon steel. The ductility of nodular cast iron is about
half that of cast steel, far better than gray cast iron.
CAST IRON is produced by resmelting a charge
of pig iron and scrap iron and removing some of the
impurities from the molten metal by using various
fluxing agents. There are many grades of cast iron,
rated as to strength and hardness. The four major kinds
of cast iron are white cast iron, gray cast iron,
malleable cast iron, and nodular cast iron. With the
exception of similarity between nodular and malleable
cast iron, there are considerable differences in the
properties of the various kinds of cast iron. The form
in which the carbon exists (graphite or cementite) and
the mode of its distribution are chiefly responsible for
the differences in properties.
Steels and other metals are classified on the basis
of the method of manufacture, method of shaping,
method of heat treatment, properties, intended use,
and chemical composition. In addition, certain steels
and other metals are often referred to by trade names.
White cast iron essentially consists of an alloy of
iron, carbon, and silicon. It is known chiefly for its
good wear resistance and as the starting point for
Alloy Steel
When classified according to the method of
manufacture, steels are known as (I) basic, open
hearth; (2) basic, electric; (3) acid, Bessemer; (4) acid,
electric; (5) acid, open hearth; or (6) basic, oxygen
furnace. The method of manufacture has a lot to do
with the properties of the finished steel, so these
distinctions are important to metallurgists and to
design engineers. Since the method of manufacture is
not usually important to the HT, these processes will
not be discussed in this training manual.
An alloy metal may be defined as an intimate
mixture of two or more elements. Any ferrous or
nonferrous metal may be alloyed to form an alloy
metal with new and desirable characteristics.
A simple alloy consists of two metals in any
proportion. An example of a simple alloy is the
combination of tin and lead, which is called solder.
The melting temperature of the lead is 621°F (327°C).
Tin has a melting temperature of 450°F (232°C).
However, as the two metals are mixed, any
combination of the two results in a lower melting
temperature than 621°F (327°C). At a certain
proportion of the metals, the lowest melting
temperature is reached. This point is called the
When classified according to the method of
shaping, steels are often referred to as cold rolled steel,
forged steel, drawn steel, and cast steel.
Classifying steels according to the method or
methods of heat treatment leads to such terms as
annealed steel, and casehardened steel.
Steel is a combination of iron and controlled
amounts of carbon. Alloy steels are created by adding
other elements to plain carbon steel. Alloy steels are
identified by the name of the alloying element or
elements, usually without reference to the carbon that
is present. Alloy steels are further identified as
low-alloy steels or high-alloy steels, depending upon
the amount of alloying material that is present. Some
elements that are alloyed with carbon steel and the
qualities imparted to steel by each are as follows:
Classifying steels according to properties gives us
such classes as corrosion-resisting steels (CRES);
heat-resisting steels; low-expansion steels; freemachining or free-cutting steels; casehardening steels;
high tensile steels (HTS); and special treatment steel
Probably the most reasonable way to classify
steels is by their chemical composition. Steels that
derive their properties primarily from the presence of
carbon are referred to merely as “steels” or sometimes
as “plain carbon steels.” Steels that derive their
properties primarily from the presence of some
alloying element other than carbon are referred to as
“alloys” or “alloy steels.” Note, however, that plain
carbon steels always contain some carbon. Note, also,
that the use of the word alloy should not really be
limited to mean an alloy steel, since there are many
alloys that contain no iron at all and are, therefore, not
CHROMIUM—Increases resistance to corrosion
and improves hardness, toughness, wear resistance,
strength, and the responsiveness to heat treatment.
MANGANESE—Increases strength and
responsiveness to heat treatment.
MOLYBDENUM—Increases toughness and
improves the strength of steel at higher temperatures.
NICKEL—Increases strength, ductility, and
TUNGSTEN—Produces dense, fine grains; helps
steel to retain its hardness and strength at high
Plain Carbon Steel
SILICON—Improves the electrical quality of the
Plain carbon steels vary in carbon content from
about 0.05 percent to as much as 1.70 percent carbon.
The properties of the steel depend upon the amount of
carbon present and the particular way in which the iron
and the carbon combine. The plain carbon steels are
known (in increasing order of the amount of carbon
present) as mild steel, low-carbon steel, mediumcarbon steel, high-carbon steel, and very-high-carbon
VANADIUM—Retards grain growth and
improves toughness.
Although ferrous metals are used aboard ship
in greater quantities than the nonferrous metals, the
nonferrous metals are nevertheless of great
importance. Copper, zinc, lead, and a large number of
nonferrous alloys are required in the construction and
maintenance of naval ships. Some of the more popular
nonferrous metals a welder encounters are copper,
brass, zinc, bronze, lead, and aluminum.
Tin is seldom used aboard ship in its pure state,
but it has many important uses as an alloying element.
Tin and lead are used together to make soft solders;
tin and copper are used together to make bronze. Tin
and tin-based alloys have, in general, a high resistance
to corrosion.
The various welding processes now make it
possible to satisfactorily weld practically all
nonferrous metals.
True brass is an alloy of copper and zinc.
Additional elements—aluminum, lead, tin, iron,
manganese, or phosphorous—may be added to give
the alloy specific properties. Rolled naval brass (also
known as Tobin bronze) is about 60 percent copper,
39 percent zinc, and 0.75 percent tin. This type of brass
is highly resistant to corrosion.
Copper is one of the most important nonferrous
metals used in the construction of a ship. It is used in
the form of sheets, tubing, wires, and in copper alloys
such as brass and bronze. It is used to give a protective
coating to other metals, and to fabricate many special
Brass sheets and strips are available in grades
known as soft, 1/4 hard, 1/2 hard, full hard, and spring.
Hardness is imparted to the brass by the process of
cold rolling. Most grades of brass can be made softer
by annealing the metal at a temperature of 800° to
The properties of copper make it extremely useful
for many applications. It is easy to work; it is ductile,
malleable, tough, strong, resistant to wear, and
machinable. Copper is highly resistant to saltwater
corrosion and is an excellent conductor of both heat
and electricity. Copper seams are usually joined by
riveting, brazing, or soldering.
A bronze made of 84 percent copper and 16
percent tin was the best metal available for tools,
weapons, and so on, before techniques were developed
for making steel. Many complex bronze alloys,
containing additional elements such as zinc, lead, iron,
aluminum, silicon, and phosphorous are now
available. The name bronze is now applied to any
copper-base alloy that looks like bronze; in many
cases, there is no longer a real distinction to be made
between bronze and brass.
Zinc is used as a protective coating (galvanizing)
on steel and iron. Zinc is also used in the form of zinc
chloride for soldering fluxes and as an alloying
element in some brass and bronze.
High-purity zinc, in the form of sheets, rods, or
special shapes, is used to protect hulls, hull fittings,
and many types of machinery from the effects of
galvanic action.
Aluminum and Aluminum Alloys
Aluminum and aluminum alloys are widely used
because they are lightweight, easily worked, and
strong in relation to their weight. There are now so
many different types of aluminum alloys in use that a
special numbering system has been adopted for these
Lead is probably the heaviest metal that you will
ever use on board ship. Lead weighs about 700 pounds
per cubic foot, but in spite of its weight, it is soft and
malleable. Lead is commonly supplied in sheet form,
rolled up on a rod. To use it, you merely unroll it and
cut off as much as you need.
Because of its softness, lead is often used as a
backing material for punching and hammering
operations. Sheet lead is used to line sinks and to
protect bench tops that are exposed to acids. Lead is
also used as a radiation shield.
Material is used daily and, normally, there will be
some material left over. Quite often the means of
marking the material was cut off, or worn off, leaving
In trying to identify a piece of metal by its surface
appearance, consider both the color and the texture of
the surface. Table 6-3 gives the surface colors of some
common metals.
the material to a guessing game as to what type of
material it is. Granted, it is best to make out a tag with
all the important information as to the type of material,
the alloy composition, and possibly the stock number
of that material. Even then, tags are subject to being
lost. Therefore, let us look at the various ways to
identify the material according to surface appearance
and identification tests.
If the surface appearance of a metal does not give
enough information to allow adequate identification,
metal identification tests are necessary. A number of
such tests are used. Some of these tests are complicated
and require equipment that you are not likely to have.
Others, however, are relatively simple and quite reliable
when performed by a skilled person. The following tests
are the most common for shop use:
It is possible to identify several metals by their
surface appearance. Although examination of the
surface does not usually give you enough information
to classify the metal exactly, it will often give you
enough information to allow you to identify the group
to which the metal belongs. Even this much
identification is helpful since it will limit the number
of tests required for further identification.
Spark test (with the power grinder)
Oxyacetylene torch test
Fracture test
Table 6-3.—Surface Colors of Some Common Metals
Color test
Density or specific gravity test
Ring or sound of the metal upon impacting
with some other metal
Magnetic test
Chip test
Spark Test
The spark test is made by holding a sample of the
material against a power grinder. The sparks given off,
or the lack of sparks, assist in identifying the metal.
The length of the spark stream, its color, and the type
of sparks are the features for which you should look.
There are four fundamental spark forms produced
by holding a sample of metal against a power grinder.
(See fig. 6-10.) View A shows shafts, buds, breaks,
and arrows. The arrow or spearhead is characteristic
of molybdenum, an alloying element in steel. When
swelling or buds are present in the spark line, nickel
is also present as an alloying element with
molybdenum. View B shows shafts and sprigs, or
sparklets, which indicate a high carbon content. View
C shows shafts, forks, and sprigs that indicate a
medium carbon content. View D shows shafts and
forks that indicate a low carbon content.
Figure 6-10.—Fundamental spark forms.
to suppress the effect of the carbon burst. However,
the nickel spark can be identified by tiny blocks of
brilliant white light. Silicon suppresses the carbon
burst even more than nickel. When silicon is present,
the carrier line usually ends abruptly in a white flash
of light.
The greater the amount of carbon present in the
steel, the greater the intensity of bursting that will take
place in the spark stream. To understand the cause of
the bursts, remember that while the spark is glowing
and in contact with the oxygen of the air, the carbon
present in the particle is burned to carbon dioxide. As
the solid carbon combines with oxygen to form carbon
dioxide in the gaseous state, the increase in volume
builds up a pressure that is relieved by an explosion of
the particle. An examination of the small steel
particles under a microscope when they are cold
reveals a hollow sphere with one end completely
blown away.
To make the spark test, hold the piece of metal
against the wheel in such a manner as to throw the spark
stream about 12 inches at a right angle to your line of
vision. You will need to spend a little time to discover
at just what pressure you must hold the sample to get a
stream of this length without reducing the speed of the
grinder. It is important that you do not press too hard
because the pressure will increase the temperature of the
spark stream and the burst. It will also give the appearance of a higher carbon content than that of the metal
actually being tested. After practicing to get the feel of
correct pressure on the wheel until you’re sure you have
it, select a couple of samples of metal with widely
varying characteristics; for example, low-carbon steel
and high-carbon steel. Hold first one then the other
against the wheel, always being careful to strike the
same portion of the wheel with each piece. With your
eyes focused at a point about one-third of the distance
from the tail end of the stream of sparks, watch only
those sparks that cross the line of vision. You will find
Steels having the same carbon content but
differing alloying elements are not always easily
identified because alloying elements affect the carrier
lines, the bursts, or the forms of characteristic bursts
in the spark picture. The effect of the alloying element
may retard or accelerate the carbon spark or make the
carrier line lighter or darker in color. Molybdenum,
for example, appears as a detached, orange-colored,
spearhead on the end of the carrier line. Nickel seems
that after a little while, you will form a mental image of
the individual spark. After you can fix the spark image
in mind, you are ready to examine the whole spark
Notice that the spark stream is long (about 70 inches
normally) in low-carbon steel, and that the volume is
moderately large; while in high-carbon steel, the stream
is shorter (about 55 inches) and larger in volume. The
few sparklers that may occur at any place in low-carbon
steel are forked, while in high-carbon steel the sparklers
are small and repeating, and some of the shafts may be
forked. Both will produce a white spark stream.
White cast iron produces a spark stream approximately 20 inches in length (see fig. 6-11). The volume
of sparks is small with many small and repeating sparklers. The color of the spark stream close to the wheel
is red, while the outer end of the stream is straw colored.
Gray cast iron produces a stream of sparks about 25
inches in length. It is small in volume with fewer
sparklers than white cast iron. The sparklers are small
and repeating. Part of the stream near the grinding wheel
is red, and the outer end of the stream is straw colored.
The malleable iron spark test will produce a spark
stream about 30 inches in length. It is of a moderate
volume with many small, repeating sparklers toward the
end of the stream. The entire stream is straw colored.
The wrought iron spark test produces a spark stream
about 65 inches in length. The stream is of large volume
with few sparklers. The sparklers show up toward the
end of the stream and are forked. The stream next to the
grinding wheel is straw colored, while the outer end of
the stream is a bright red.
Stainless steel produces a spark stream approximately 50 inches in length, of moderate volume, with
few sparklers. The sparklers are forked. The stream next
to the wheel is straw colored. The sparks form wavy
streaks with no sparklers.
Monel metal forms a spark stream almost identical
to that of nickel and must be identified by other means.
Copper, brass, bronze, and lead form no sparks on the
grinding wheel, but they are easily identified by other
means, such as color, appearance, and chip tests.
You will find the spark tests easy and convenient to
make. They require no special equipment and are adaptable to most any situation. Here again, experience is the
best teacher.
It is good practice to compare the sparks of an
unknown metal with those of a known metal. This
permits an additional check on the tester’s conclusion
and also can distinguish between different metals that
Figure 6-11.—spark pictures formed by common metals.
have similar spark patterns. It is the practice in many
metal shops to maintain a cabinet of commonly used
metals, positively identified as to grade, for comparison with unknown samples.
Proper lighting conditions are essential for good
spark testing practice. Testing should not be done in
strong direct lighting. A dark background for the spark
may have been done to the metal affecting its
properties. The metal may not melt and fuse readily.
The final weld may be unsatisfactory. The usual cause
of this condition is that there are impurities imbedded
in the metal. The impurities are usually slag and roller
dirt or excessive sulphur and phosphorus. For these
reasons, a welder should subject steel to the torch test.
pattern should be used. Heavy drafts of air against the
spark pattern should be avoided as the air can change
the tail sparks. Such a change will lead to incorrect
Oxyacetylene Torch Test
Metals may sometimes be identified by their
characteristic reactions to being heated with an
oxyacetylene welding torch. Identifying factors
include the rate of melting, the appearance of the
molten slag, and the color changes (if any) that occur
during the heating. Table 6-4 indicates the reactions
of various metals to the torch test.
Even if you know the physical composition and
the chemical composition of a metal, you must also
know whether the metal has good welding properties.
For example, some cold rolled sheet steels may show
very good physical and chemical properties. However,
during some part of the manufacturing process,
impurities may have been added to it or certain work
Table 6-4.—Identification of Metals by Oxyacetylene Torch Test
Reactions When Heated By Oxyacetylene Torch
White cast iron
Metal becomes dull red before melting. Melts at moderate rate. A medium tough film of slag develops. Molten
metal is watery, reddish white in color, and does not show sparks. When flame is removed, depression in
surface of metal under flame disappears.
Gray cast iron
Puddle of molten metal is quiet, rather watery, but with heavy, tough film forming on surface. When torch
flame is raised, depression in surface of metal disappears instantly. Molten puddle takes time to solidify, and
gives off no sparks.
Malleable iron
Metal becomes bright red before melting: melts at moderate rate. A medium tough film of slag develops, but
can be broken up. Molten puddle is straw colored, watery, and leaves blowholes when it boils. Center of
puddle does not give off sparks, but the bright outside portion does.
Wrought iron
Metal becomes bright red before it melts. Melting occurs quietly and rapidly, without sparking. There is a
characteristic slag coating, greasy or oily in appearance, with white lines. The straw-colored molten puddle
is not viscous, is usually quiet but may have a tendency to spark; is easily broken up.
Low-carbon and Melts quickly under the torch, becoming bright red before it melts. Molten puddle is liquid, straw colored,
cast steel
gives off sparks when melted, and solidifies almost instantly. Slag is similar to the molten metal and is quiet.
Metal becomes bright red before melting, melts rapidly. Melting surface has cellular appearance, and is
brighter than molten metal of low-carbon steel; sparks more freely, and sparks are whiter. Slag is similar to
the molten metal and is quiet.
Stainless steels
Reactions vary depending upon the composition.
Metal has high heat conductivity; therefore, larger flame is required to produce fusion than would be required
for same size piece of steel. Copper color may become intense before metal melts; metal melts slowly, and
may turn black and then red. There is little slag. Molten puddle shows mirror like surface directly under flame,
and tends to bubble. Copper that contains small amounts of other metals melts more easily, solidifies more
slowly, than pure copper.
Brass and
These metals melt very rapidly, becoming noticeably red before melting. True brass gives off white fumes
when melting. Bronze flows very freely when melting, and may fume slightly.
Aluminum and
Melting is very rapid, with no apparent change in color of metal. Molten puddle is same color as unheated
aluminum alloys metal and is fluid; stiff black scum forms on surface, tends to mix with the metal, and is difficult to remove.
Melts more slowly than steel, becoming red before melting. Slag is gray scum, quiet and hard to break up.
Under the scum, molten puddle is fluid and quiet.
Melts slowly (about like Monel), becoming red before melting. Slag is gray scum, quiet and hard to break up.
Under the scum, molten puddle is fluid and quiet.
Melts at very low temperature, with no apparent change in color. Molten metal is white and fluid under a thin
coating of dull gray slag. At higher temperature, puddle boils and gives off poisonous fumes.
Chip Test
The actual test consists of melting a puddle in the
steel. If the metal is thin, the puddle penetrates through
the thickness of the steel until a hole is formed. This
puddling should be done with a neutral flame, held at
the proper distance from the metal. The puddle should
not spark excessively or boil. The puddle should be
fluid and should possess good surface tension. The
appearance on the edge of the puddle or hole indicates
the weldability of the steel. If the metal that was
melted has an even, shiny appearance upon
solidification, the metal is generally considered as
having good welding properties. However, if the
molten metal surface is dull or has a colored surface,
the steel is unsatisfactory for welding. The steel is also
considered unsatisfactory for welding if the surface is
rough, perhaps even broken up into small pits or
porous spots.
Another test that must be accompanied by
considerable experience is the chip test. To make a
chip test, use a sharp cold chisel to remove a small
amount of metal from a sample. The ease with which
the chipping can be done gives some indication of the
kind of metal with which you are working. The size,
form, and color of the chips and the appearance of the
edges (whether smooth or sawtoothed) give further
In this test, the cutting action of the chisel
indicates the structure and heat treatment of the metal.
Cast iron, for example, when being chip-tested, breaks
off in small particles, whereas a mild steel chip tends
to curl and cling to the original piece. Higher-carbon,
heat-treated steels cannot be tested this way because
of hardness. A rough test between mild carbon steel
and chrome-moly steel may be indicated by the
relative hardness of the metals while being
This test is accurate enough for most welding. The
test is very easily applied with the equipment on the
job. The test determines the one thing that is
fundamentally necessary in any welding job, that is,
the weldability of the metal. Figure 6-12 shows how
this test is conducted. While performing the
weldability test of the metal, it is important to note the
amount of sparking emitted from the molten metal. A
metal that emits few sparks has good welding
You will not be able to identify metals by the chip
test method until you have had considerable
experience. You should practice with samples of
known metals until you have learned how to identify
carbon steel, carbon-molybdenum steel,
chromium-molybdenum steel, chromium-nickel steel,
and other metals. The information given in table 6-5
will help you to recognize some of the more common
Fracture Test
The fracture test is used extensively and consists
of breaking a portion of the metal in two. If it is a repair
job, the fractured surface may be inspected. The
appearance of the surface where the metal is cracked
shows the grain structure of the metal. If the grains are
large, the metal is ductile and weak. If the grains are
small, the metal is usually strong and has better
ductility. Small grains are usually preferred. The
fracture shows the color of the metal, which is a good
means of identifying one metal from another. The test
also indicates the type of metal by the ease with which
it may be fractured.
Color Test
The color test separates two main divisions of
metals. The irons and steels are indicated by their
typical gray white color. Nonferrous metals come in
two general color classifications of yellow and white.
Figure 6-12.—Torch flame test: (A) Good quality filler rod. (B)
Poor quality filler rod. (C) and (D) Good quality base
metal. (E) and (F) Poor quality base metal.
Table 6-5.—Identification of Metals by Chip Test
Copper, brass, and bronze can be rather easily
identified by a welder. Aluminum is a white metal.
Aluminum alloys, zinc, and the like, are all of
somewhat the same silver-gray color although they
may vary in shade.
Ring Test
The ring test, or the sound of the metal test, is an
easy means of identifying certain metals after some
experience with this method. It is used extensively for
identifying heat-treated steels from annealed steels. It
is also used to detect alloys from the virgin metal. An
example is the difference between aluminum and
duralumin, an alloy of aluminum and copper (2017-T)
(the letter T indicates that the metal is heat treated).
The pure aluminum sheet has a duller sound, or ring,
than the duralumin, which is somewhat harder and has
a more distinct ringing sound.
Density Test
Metals may also be differentiated by means of the
weight or density test of the specimen. A good
example of identification by density or specific
gravity is identifying aluminum and lead. Roughly
speaking, their colors are somewhat similar, but
anyone may readily distinguish between the two
metals because of their respective weights. Lead
weighs about three times as much as aluminum.
Magnetic Test
The magnetic test is another method used to aid in
the general identification of metals. Frequently, the
tungsten reacts slowly to form a brown-colored liquid
with a yellow sediment.
inexperienced person confused aluminum and
stainless steels. Remember that ferrous metals, being
iron-based alloys, are magnetic whereas nonferrous
metals are nonmagnetic.
Instead of the brown-black colors that usually
appear when ferrous metals are tested, various shades
of green and blue appear as the material dissolves
when nonferrous metals and alloys are subjected to the
nitric acid test. Except with nickel and Monel, the
reaction is vigorous. The reaction of nitric acid on
nickel proceeds slowly, developing a pale green color.
On Monel, the reaction takes place at about the same
rate as on ferrous metals, but the characteristic color
of the liquid is greenish-blue. Brass reacts vigorously,
with the test material turning to a green color. Tin
bronze, aluminum bronze, and copper all react
vigorously in the nitric acid test, with the liquid
changing to a blue-green color. Aluminum and
magnesium alloys, lead, lead-silver, and lead-tin
alloys are soluble in nitric acid, but the blue or green
color is lacking.
Nitric Acid Test
The nitric acid test is one of the easiest tests to
distinguish between stainless steel, Monel, copper
nickel, carbon steels, and various other metals. You
need no special training in chemistry to perform this
test. However, you must observe the following safety
precautions when using or handling acids of any type:
— Never open more than one container of acid at
one time.
— Use only glass containers when mixing or
stowing acids.
— In mixing, always pour acid slowly into water.
NEVER pour water into acid, because an
explosion is likely to occur.
From the information given thus far, it is easy to
see that it will require considerable visual skills to
identify the many different reactions of metals to nitric
acid. As an HT, you will be mostly concerned with the
identification of stainless steel, Monel, and carbon
— If any acid is spilled, dilute it with plenty of
water to weaken it so that it can safely be
swabbed away.
— If an acid is spilled on the skin, wash
immediately with large quantities of water.
Then wash with a solution of borax and water.
File Hardness Test
Hardness tests are commonly used to determine
the ability of a material under test to resist abrasion or
penetration by another material. Many methods have
evolved for measuring the hardness of metal. The
simplest method is the file hardness test. This test
cannot be used to make positive identification of
metals but can be used to get a general idea of the type
of metal being tested and to compare the hardness of
various metals on hand. Thus, when identification of
metal by other means is not possible, you might use a
file to determine the relative hardness of various
metals. The results of such a test may enable you to
select a metal more suitable for the job being
— Wear safety goggles. Clear-lens goggles will
make it easier to detect the reaction of a metal
to an acid test, which may be evidenced by a
color change, the formation of a deposit, or the
development of a spot.
— Conduct tests in a well-ventilated area.
To perform the nitric acid test, place one or two
drops of concentrated (full strength) nitric acid on a
metal surface that has been cleaned by grinding or
filing. Observe the resulting reaction (if any) for about
2 minutes. Then add three or four drops of water, one
drop at a time, and continue observing the reaction. If
there is no reaction at all, the test material may be one
of the stainless steels.
The file hardness test is simple to perform. The
metal being tested may be held by hand and rested on
a bench, or held in a vise. Grasp the file, with the index
finger extended along the file, and apply the file
slowly but firmly to the surface being tested.
The reaction that results in a brown-colored liquid
indicates a plain carbon steel. A reaction producing a
brown to black color indicates a gray cast iron or one
of the alloy steels containing as its principal element
either chromium, molybdenum, or vanadium. Nickel
steel reacts to the nitric acid test by forming a brown
to greenish-black liquid, while a steel containing
If the material is cut by the file with extreme
ease and tends to clog the spaces between the file
teeth, it is VERY SOFT. If the material offers some
resistance to the cutting action of the file and tends to
clog the file teeth, it is SOFT. If the material offers
considerable resistance to the file but can be filed by
repeated effort, it is HARD and may or may not have
been heat treated. If the material can be removed only
by extreme effort and in small quantities by the file
teeth, it is VERY HARD and has probably been heat
treated. If the file slides over the material and the file
teeth are dulled, the material is EXTREMELY HARD
and has been heat treated.
This chapter has given you a thorough overview
of basic metallurgy. Remember, it is basic information
only, and you will need to learn specific applications
through experience and by further study in the appropriate technical manuals. Always ask a senior member
of your division to explain anything in this chapter or
in your work that you do not fully understand.
You have been introduced to stresses and strains,
the structure, properties, and types of metals, and the
ways in which metals are classified, marked, and
tested. Go back now and review any of these areas that
you do not understand.
The file test is not a scientific method. It should
not be used when positive identification of metal is
necessary or when an accurate measurement of hardness is required.
Upon completion of this chapter, you will be able to do the following:
Identify the principle welding processes and define terms used in basic
Identify the various welding symbols.
Describe the types and techniques of edge preparation in welding.
Describe the purpose of temperature control during and after the welding
process has been performed.
Describe the pipe welding process, and identify the different classes of piping.
Identify the principle cutting processes.
Name the important publications concerning military standards and
qualification tests with which a welder should be familiar.
One of the primary requirements for Hull
Maintenance Technicians is to make various metal
objects and structures. Most of these will require
welding and cutting metal. Study and practical
experience are both necessary to become an expert
welder. This chapter contains essential background
information that will help you to learn the welding
processes and to qualify for advancement. Most of
the terms, phrases, and processes discussed in this
chapter are standardized, and are used in the Navy
as well as by civilians in the welding trades. At
times, the information in this chapter may seem
complex, but you need a thorough knowledge of it
to perform the duties of your job. Study this
chapter carefully so you can effectively assist skilled
welders and eventually become a good welder
A master chart of welding processes is shown in
figure 7-1. The term WELDING PROCESS means
that you heat metal parts to a temperature that is
high enough to join the metal parts by coalescence.
It is done with or without the use of pressure or by
the pressure alone, and it can be done with or
without the use of filler metal. Coalescence means
the growing together, or growth into one body, of
There are two basic
the base metal parts.
requirements for coalescence: heat and intimacy of
The welding processes differ depending on the
source of heat, the manner in which heat is applied
or generated, and the intensity of the heat. The
source of heat may be the combustion of a fuel gas
Figure 7-1.—Welding processes.
processes except brazing use temperatures high
enough to melt the base metals. Brazing is the
ONLY welding process in which the melting of the
base metal is not necessary for coalescence. Brazing
is similar to soldering, except that higher
temperatures are used for brazing. The term
SOLDERING is used to describe a joining process
using nonferrous filler alloys melting below 800°F
(427°C). Soldering is NOT considered a welding
process. Brazing is a welding process using
nonferrous filler alloys that have a melting point
above 800°F (427°C) but below that of the base
such as acetylene or hydrogen in air or in oxygen;
an electric arc; an electric, gas, or oil furnace; the
resistance of metal to the flow of electric current; or
a chemical reaction between a metal oxide and
finely divided aluminum. The welding processes
most commonly used aboard ship involve the
combustion of a fuel gas, as in oxyacetylene welding
and torch brazing; the use of an electric arc, as in
metal-arc welding; and the resistance of metal to the
flow of electric current, as in spot welding.
The intensity of heat applied or generated at the
joint varies according to the metals being joined and
to the welding process being used. All welding
elaborate preparations, fluxes, and special
techniques because its characteristics are such that
the welding operation can be easily performed.
Other metals require special preparatory steps,
complex welding sequences, skillful use of a specific
welding technique, and extensive heat treatments
after welding.
In the second basic requirement for coalescence,
intimacy of contact, the welding processes may be
divided into two groups: pressure processes and
nonpressure processes. In PRESSURE
PROCESSES, we get intimacy of contact by
applying pressure while the contact surfaces are at
a high enough temperature to allow plastic flow of
space is left between the surfaces to be joined. This
space is filled, either progressively or all at once,
with molten metal. The molten metal may be
obtained from a filler metal (welding rod or
electrode), by melting the surfaces to be joined, or
by combining a filler metal and melted base metal.
Many factors influence the weldability of a
metal. Here are some of the more important ones
that must be taken into account and, insofar as
possible, controlled: (1) the chemical composition
of the metals involved (that is, the kind and
percentage of elements present) and the effect of
radical temperature changes on the various
elements; (2) the expansion and contraction
characteristics of the base metals; (3) the filler metal
(welding rod or electrode); (4) the joint design; and
(5) the welding procedure.
All nonpressure processes involve fusion, and
are often referred to as FUSION PROCESSES.
However, this term is somewhat misleading since
some pressure processes also involve fusion.
The Navy uses a large number of different
metals and alloys. Each of these materials has
characteristics or properties that make its use
desirable for certain applications.
characteristics and properties of a given alloy are
partly determined by the kind and amount of
elements present. The effect welding has on these
elements and their reaction during and after the
application of heat have a tremendous influence on
the weldability of the metal in question.
The various welding processes differ not only in
the way coalescence is achieved, but also in their
ability to produce a satisfactory joint in a given kind
of metal under the conditions in which the weld
must be made. Many factors influence the selection
of a welding process for a particular application.
Some important factors to be considered are the
relative cost, the amount of welding required, the
location and position of welds, the service conditions
the welded structure must withstand, and the
qualifications of the person who does the welding.
Probably the most important single factor, however,
is the weldability of the metal.
In steel, carbon is probably the most important
element that limits weldability. Carbon gives steel
hardenability; that is, when certain carbon steels are
heated above a critical temperature and then cooled
rapidly, they be come much harder. At the same
time they lose ductility. In fact, the metal may
become extremely brittle. With few exceptions, the
temperatures used in welding exceed the critical
temperature of carbon steels.
Further, more
hardening may occur when the mass of relatively
cold metal surrounding the weld area conducts heat
away so fast that rapid cooling occurs. Thus, certain
steels may become hardened by many of the welding
The term WELDABILITY means the capacity
of a metal to be fabricated by a welding process into
a structure that will perform its purpose
satisfactorily. Weldability also means the degree of
simplicity or complexity of the procedures and
techniques used to produce welds with properties
that are equal to or better than the properties of the
base material. For example, mild steel can be
welded by most welding processes, but the welds
produced may not be equally satisfactory, and one
method may be more complicated or more
expensive than another. While it is possible to weld
mild steel through the use of a variety of welding
processes, some metals such as aluminum and its
alloys can be satisfactorily welded with only a few
welding processes. Mild steel does not require
When the percentage of carbon is less than 0.25
percent, its effect in producing hardness is slight.
But when the carbon content exceeds 0.25 percent,
or when such elements as manganese, vanadium,
chromium, molybdenum, or titanium are present,
along with a lesser carbon percentage, the
weldability of the steel is decreased. Special steps
should be taken to control preheat, interpass
temperature, postheat, and welding sequence.
Otherwise, a satisfactory weld is likely to crack and
to have reduced toughness and less strength than is
required. For this reason, tool steels and certain
alloys like carbon-molybdenum steel are less
weldable than many other steels.
Even when the weld joins identical metals, or
metals having approximately the same coefficient of
expansion, the expansion and contraction may not
be uniform throughout all parts of the metal. These
differences lead to internal stresses, distortion, and
warping. Metal parts must be free to move or a
special weld sequence must be used. When heat is
applied or withdrawn, expansion and contraction set
up high stresses, which in turn may cause trouble in
the weld itself or in the adjacent base metal. In thin
materials, uneven expansion and contraction may
cause the metal to warp. In heavy material, the
stresses set up may exceed the ultimate strength of
the metal and cause cracking to occur in the weld or
in the metal next to the weld, which is called the
heat affected zone.
Steels contain certain impurities such as sulfur,
phosphorus, hydrogen, nitrogen, and oxygen. If
present in large enough quantities, these impurities
may decrease weldability. For example, a steel to
which about 0.10 percent sulfur has been added to
improve machinability is difficult to weld because
the weld has a tendency to crack. An excessive
amount of phosphorus decreases the ductility of the
steel and thus decreases the weldability of the metal.
The presence of hydrogen in a steel, filler material,
or flux may lead to cracks in the welds.
Even if the ultimate strength of the material is
not exceeded by the stresses developed during
welding, the combination of welding stresses PLUS
the stresses developed when the material is placed
in service may be enough to cause failure of the
weld. It is for this reason that many materials are
STRESS RELIEVED after welding.
Stainless steels, high-chromium steels, and other
special steels are less weldable than the plain
low-carbon steels. The elements that give these
special steels their desirable properties for some
applications also have the effect of decreasing the
weldability of the metals. To make these special
steels weldable, the welding procedures, the filler
metal, the fluxes, the preheat and postheat
temperatures, and the welding sequence must be
carefully selected. This is also true for many nickel,
copper, and aluminum alloys.
Another factor that influences weldability is the
filler material used. The wrong electrode or
incorrect welding process will make welding difficult
or impossible, and it may lead to failure of the part
under service conditions. It is not always essential
that the welding rod or electrode be of the same
chemical composition as the base metal; the
important requirement is that the combination of
the filler metal and the base metal will make a
satisfactory welded joint.
In some metals, the heat of the welding process
may cause certain elements with low-melting points
to vaporize, thus reducing the amounts of those
elements present in the weld zone. Nonferrous
alloys containing lead, zinc, and tin are particularly
subject to such losses from vaporization. These
losses may seriously affect the properties of the joint
by causing porosity or oxide inclusions that weaken
the weld.
In some processes, the flux selected for use with
a welding rod has important effects on weldability.
Also, the electrode covering influences the weld
obtained in certain steels. Molten steels have a
tendency to absorb hydrogen from the surrounding
atmosphere and to expel it when they solidify.
Some types of electrode coverings send a lot of
hydrogen into the atmosphere surrounding the arc
and the molten puddle. This hydrogen is frequently
enough to cause microscopic cracks in the
heat-affected zone of some steels. To eliminate this
problem, low-hydrogen electrodes have been
developed to weld the newer high-tensile steels.
The weldability of a metal is also affected by its
thermal conductivity. In general, metals with high
thermal conductivity are difficult to weld because
they transfer the heat away from the weld so rapidly
that the required temperature cannot be maintained
at the joint.
Changes in temperature cause a metal to expand
or contract and that also affects weldability. When
metals expand and contract at different rates, the
internal stresses set up by these changes can cause
the joint to crack immediately or to crack later
under load.
Joint design also influences the weldability of a
metal. You need to consider several factors when
you select a joint design. They include the welding
A BUTT joint is used to join the edges of two
members lying in approximately the same geometric
plane. The joint area is between the edges of the
two members. This type of joint is frequently used
in plate, sheet metal, and pipe work.
process, the thickness of the material to be welded,
and the purpose the joint is to serve.
You can butt together thin sheets of metal
without special preparation other than cleaning.
But heavy plates must be beveled or grooved to
make a satisfactory joint. Again, the design used is
related to the purpose of the joint; that is, the way
the load or stress is applied, the erosive or corrosive
conditions it must resist, and the joint efficiency.
The term JOINT EFFICIENCY is used to indicate
the strength of a welded joint as compared with the
strength of the unwelded base metal.
EDGE joints also may be used to join parallel
members lying in the same plane, but as a rule one
of the members is flanged. The edge joint in figure
7-2 shows that the members need not be in the
same plane, as the members of a butt joint must be.
With edge joints, the joint area is between the
contacting surfaces of the members. While this type
of joint has some applications in plate work, it is
more often used in sheet metal work. In many
cases, no filler metal is used in joining edge joints by
the gas welding process. The edges are fused
together, and the base metal supplies the weld filler
metal. Occasionally the edge joint is used to join
reinforcing plates to the flanges of I-beams and the
edges of angles.
The terminology used to describe the various
kinds of joints and the parts of a welded joint is
discussed and illustrated later in this chapter.
Details of joint designs for various applications and
different welding processes are covered by
specifications. At this point, you need to know only
that joint design affects weldability.
As noted before, metals are not equally weldable
with all welding processes. You should select a
welding process on the basis of specifications and
pertinent instructions from the Naval Sea Systems
Command. For example, aluminum-base alloys are
weldable by a number of processes. However, the
Naval Sea Systems Command does not permit the
welding of these alloys aboard ship by any welding
process other than gas shielded-arc welding. These
specifications and instructions must also be used to
select base metals, filler metals, fluxes, and welding
CORNER joints and TEE joints are used to join
two members located at approximately right angles
to each other. The joint area in each case is
between the end of one member and the side or
edge of another. The corner joint forms an L-shape
(fig. 7-2). Corner joints are used to make tanks,
boxes, box frames, and similar objects. Only
Each of the welding processes has a technique
or procedure peculiar to that process. Often the
technique varies with the kind or size of the filler
metal used or the kind of weld being made. The
incorrect use of a technique, or the use of the wrong
technique, may lead to defects that make the joint
Five basic types of welded joints are used in
welded structures: butt, edge, tee, corner, and lap.
There are many variations, but every joint you
weld will be one of these basic types. The joint area
in each case is indicated by the shaded portion of
the drawings in figure 7-2.
Figure 7-2.—Types of welded joints.
Several types of bead and fillet welds are
illustrated in figure 7-3. Usually a BEAD WELD
(fig. 7-3, view A) is made by depositing filler metal
in a single direction on an unbroken surface.
However, it is also possible to make a bead without
adding filler metal. In this case, the heat is applied
and moved along steadily in one direction so that a
molten puddle is formed in the base metal. Bead
welds are used principally on butt joints and as a
way of building up surfaces. The cross section of a
bead weld usually has an oval shape.
very-low-pressure tanks use corner joints because
the root of the weld is in tension under load. The
tee joint forms the shape of the letter T. Tee joints
are used in many types of metal structures. The tee
joint distributes stress more evenly throughout the
The LAP joint is used to join overlapping
members of a structure. The joint area of a lap
joint is between the parallel surfaces of the joint
members. Lap joints are often used in torch brazing
processes where capillary action draws filler metal
into the space between the hot surfaces. They are
also used in many resistance welding processes,
especially in sheet metal structures fabricated with
spot welds.
A FILLET WELD is triangular in cross section.
It joins two surfaces that are at approximately right
angles to each other. Fillets are used to weld lap,
tee, and corner joints. As shown in views B, C, and
D of figure 7-3, some variations of the fillet weld
are chain intermittent, staggered intermittent, and
The types of welds most commonly used aboard
ship are bead welds, fillet welds, tack welds, groove
welds, plug welds, slot welds, spot welds, and seam
welds. Another term that you will hear quite often
is SEAL WELD. This term does not actually refer
to any one type of weld; rather, it is any weld that
is used primarily to obtain tightness.
A TACK WELD is a short weld deposit made
to temporarily hold the parts to be joined in proper
alignment for final welding. The sizes of tack welds
are usually not specified, but they must not exceed
1 inch in length, and they must be as small as can
be made, consistent with the size of the electrode
being used. Tack welds must be incorporated into
Figure 7-3.—Bead and fillet welds.
the finished weld. Cracked or broken tack welds
must be chipped or ground out before the joint is
finally welded.
plates that are not otherwise accessible for welding.
A plug weld is a circular weld made through one
member of a lap or tee joint to join that member to
another. The plug weld may or may not be through
a hole punched or cut in the first member. If a hole
is used in the first member, the plug weld may fill it
completely or it may fill it only partially. A slot
weld is similar to a plug weld, except that an
elongated hole is made in the first member of the
joint. The hole may be completely or partially filled
with weld metal. Slot welds are often used to join
one plate to the surface of another plate, and for
other purposes where a fillet weld would not be
economical or would not be a good design.
Incidentally, a fillet weld made at the intersection of
the edge of a slot and the exposed surface of the
joining member is considered a fillet weld, NOT a
slot weld.
GROOVE WELDS are made in a specially
prepared groove between two members to be joined.
While the edge of a vertical plate of a tee joint is
sometimes beveled for welding, grooves are most
frequently used for butt joints in plate and pipe
work. Standard grooves for plates joined with butt
joints are illustrated in figure 7-4. Groove welds are
designed to provide the required strength with a
minimum amount of filler metal. Plate edges may
be prepared for groove welding by shearing,
machining, chipping, grinding, flame cutting, or
flame grooving, depending on the metal. The
selection of a particular groove design is governed
by the thickness of the plate to be welded, the
adaptability of the design to the structure, and the
accessibility of the joint for welding. For example,
a joint that can be welded from only one side
requires a different groove design than a joint that
is accessible from both sides.
common types of resistance welds. These welds are
shown in figure 7-6.
In resistance welding,
coalescence is produced by a combination of
pressure and the heat obtained from the resistance
of the base metal to the flow of an electric current.
A spot weld is used only when the parts of the joint
illustrated in figure 7-5, are used to join overlapping
Figure 7-4.—Standard groove welds.
Figure 7-5.—Plug and slot welds.
Figure 7-6.—Spot weld and seam welds.
More commonly, however, seam welds are made
with a wheel-type electrode.
overlap. The size and shape of the weld (often
called the nugget) are determined by the size and
shape of the electrode tips used in the welding
machine. A seam weld is very much like a spot
weld and may, in fact, be made as a series of
overlapping spot welds, as shown in figure 7-6.
You should be familiar with the terms used to
describe the parts of welds. Figure 7-7 illustrates
the face and the toe on groove and fillet welds. The
FACE is the exposed surface, on the side from
which the weld was made, of a weld made by a gas
or arc welding process. The TOE is the junction
between the face of the weld and the base metal.
The ROOT of a weld includes the points at
which the bottom of the weld intersects the base
metal surfaces, as seen in cross section. Figure 7-8
illustrates weld roots.
Figure 7-7.—Face and toe of groove and fillet welds.
Figure 7-8.—Weld roots.
thermal conductivity of the metal. The changes that
occur within the area are related to the kind of
metal being welded, the intensity and duration of
heat, and the control embodied in the welding
The legs and throat of a fillet weld are shown in
figure 7-9. When we look at a triangular cross
section of a fillet weld, the LEG is the portion of
the weld from the toe to the root. The THROAT
is the distance from the root to a point on the face
of the weld along a line that would form a
90-degree angle with the weld face, as shown in
figure 7-9.
To follow the specifications for any welding job,
you must have a very clear knowledge of the terms
used to describe parts of welds, and those used to
describe parts of joints. The similarity in terms may
lead to confusion. For example, the root of a weld
is NOT precisely the same as the root of a joint. In
other cases, it may be somewhat difficult to decide
whether a term really refers to a part of a weld or
to a part of a joint. In all cases, it is essential that
you know EXACTLY what part, zone, or
measurement is being referred to.
Theoretically, the face is considered to form a
straight line between the toes. If the face of the
weld is convex or concave, it will not form a straight
line between the toes. In that case, the actual face
will be larger than the theoretical face, and the
actual throat will be either larger or smaller than
the theoretical throat. It should be noted that the
terms LEG and THROAT apply only to fillet welds.
Several other terms are used to describe areas
or zones of welds. Figure 7-10 illustrates the use of
some of these terms. The BOND is the junction of
the weld metal and the base metal. If weld metal is
not used, the junction of the base metal parts is
used. FUSION is the melting together of base and
filler metal, or the melting of base metal only, that
results in coalescence. The FUSION ZONE is the
region of the base metal that is actually melted.
The DEPTH OF FUSION is the distance that
fusion extends into the base metal from the surface.
Both the fusion zone and the depth of fusion are
considered in terms of a cross section of the weld,
as shown in figure 7-10. Another zone of interest to
the welder is the HEAT-AFFECTED ZONE, also
shown in figure 7-10. This zone includes that
portion of the base metal that has not been melted
but in which the properties and structure of the
metal have been affected by the heat of welding or
cutting. The extent of this zone varies with the
Figure 7-10.—Fusion zone, depth of fusion, heat-affected
zone, and bond of weld.
Figure 7-9.—Legs and throat of fillet weld.
Figure 7-11 shows that the GROOVE FACE is
that surface of a member that is included in the
groove. The ROOT of a joint is that portion of the
joint where the members approach each other most
closely. The root of a joint may be a point, a line,
or an area when viewed in cross section. A given
joint design may have a ROOT FACE or it may
have a ROOT EDGE. A root face is the surface of
the groove that is adjacent to the root of the joint.
If the root face is of zero width, it is known as a
root edge (fig. 7-11, view C).
Details of joint design involve the size of the
groove and the space existing between the members
of the joint. Specifications for joint design are
expressed in terms of bevel angle, groove angle,
groove radius, and root opening. Figure 7-12
illustrates the use of these terms.
Figure 7-12.—Bevel angle, groove angle, groove radius, and
root opening.
The GROOVE RADIUS is the radius of the
curved portion of the opening at the bottom of the
groove near the root of the joint. It exists only in
special groove joint designs.
The BEVEL ANGLE is the angle formed
between the prepared edges of a member and a
plane perpendicular to the surface of the member.
The ROOT OPENING refers to the separation
between the members of the joint where the
members are closest together.
The GROOVE ANGLE is the included angle of
the groove between the parts to be joined. For
example, if the edge of each of the two plates to be
joined were beveled to an angle of 30°, the groove
angle would be 60°.
The bevel angle, groove angle, and root opening
of any joint will depend upon the thickness of
material being welded, the kind of joint being made,
and the welding process being employed. As a rule,
oxyacetylene welding requires a larger groove angle
than does manual metal-arc welding. Root opening
is usually governed by the diameter of the filler
material, which in turn depends on the thickness of
the base metal and the position of welding.
Root penetration and joint penetration in
groove welds are illustrated in figure 7-13. ROOT
PENETRATION refers to the depth that a groove
weld extends into the root of the joint. Root
penetration is measured on the center line of the
root cross section. JOINT PENETRATION refers
to the minimum depth that a groove weld extends
from its face into a joint, exclusive of any excess
weld metal that is above the plate surface.
Incidentally, this brings up another term you should
know: REINFORCEMENT OF WELD is the term
used to describe weld metal, on the face of a groove
weld, that is in excess of the metal necessary for the
specified weld size.
As may be seen from figure 7-13, the terms
PENETRATION often refer to the same dimension.
This is the case in views A, C, and E of the
Figure 7-11.—Groove face, root face, and root edge.
Figure 7-13.—Root penetration and joint penetration of groove
Figure 7-14.—Flat, horizontal, vertical, and overhead
positions for welding.
View B, however, shows how a
difference may exist between root penetration and
joint penetration. View D shows joint penetration
In the HORIZONTAL position of welding (fig.
7-14, view B), the structural members of the joint
are in an approximately vertical position while the
line of weld (axis) is approximately horizontal. A
horizontal position fillet weld is slightly different
from that of a horizontal groove weld. Welding a
fillet in the horizontal position involves depositing
filler metal on the upper size of a horizontal surface
and against an approximately vertical surface. The
face of a fillet weld lies in a plane approximately 45°
to the surfaces of the parts joined.
Welding is performed in several different
positions. In plate work, as shown in figure 7-14,
these positions are flat, horizontal, vertical, and
overhead. When welding is performed in the FLAT
position (fig. 7-14, view A), the welder works from
the upper side of the joint. In this position, the
upper surface of the weld deposit metal is in a
horizontal plane. Note that this is the case in both
flat position fillet and groove welds.
When welding is performed in the VERTICAL
position (fig. 7-14, view C), the axis of the weld is in
a vertical plane. In the vertical position, weld metal
is usually deposited in an upward direction.
In the OVERHEAD position (fig. 7-14, view D),
welding is performed from the underside of the
joint. The axis of the weld is in a horizontal plane,
as is the axis of a flat position weld. But the
overhead weld is, you might say, upside down if
compared to the flat position weld. The terms
OVERHEAD adequately describe the positions in
which plate is welded. This terminology, however,
does not describe the positions for welding pipe.
When you weld pipe, you will weld in one of three
positions: horizontal rolled position, horizontal
fixed position, and vertical fixed position. Pipe
welding positions are illustrated in figure 7-15. In
each case, the terminology refers to the axial
position and rotational freedom of movement of the
pipe, not to the weld.
the axis of the pipe is horizontal. The joint is made
by welding in the flat position, at the same time
rotating the pipe at a rate equal to the speed of
filler metal deposition. Pipe welded in the
horizontal rolled position is first carefully aligned
and tack welded. Then it is placed in a jig, which
facilitates rotation of the pipe. View A of figure
7-15 shows that all welding should be accomplished
between points A and B.
Figure 7-15.—Positions for welding pipe.
beginning. There are many details. Each must be
worked out in such a way that the completed job
serves the purpose for which it is intended.
To learn how to select a welding process, you
must first understand the terms in which the job
plans are expressed.
A single part of a structure consisting of several
parts is called a COMPONENT. When a structure
is made up of several components joined by welding,
the structure is called a WELDMENT. Typical
examples of weldments are gun mounts, machinery
foundations, storage tanks, pressure tanks, frames,
valve manifolds, and fabricated pipe fittings like
crosses, tees, and elbows. The detailed plan worked
out for producing the weldment is known as the
procedure specifies the kind of welding materials,
joint design, preheat temperature, interpass
temperature, postheat temperature, the
chronological order and manner in which a series of
joints are to be welded, and the way individual
welds in the series are to be made. The
chronological order of making the various welds in
the weldment is called the WELDING
SEQUENCE. Thus, the welding procedure spells
out all the details for producing a given weldment
with a predetermined welding process.
The pipe axis in a HORIZONTAL FIXED
POSITION weld is the same as in the horizontal
rolled position weld. In this position, however, the
pipe cannot be rotated. As a consequence, welding
must be accomplished by progression through the
overhead, vertical, and flat welding positions. When
you are welding in the horizontal fixed position (fig.
7-15. view B), the weld is started at the bottom and
progresses in increments upward to the top of the
pipe-first on one side, then on the other.
pipe axis is vertical and held in a fixed position.
The weld itself is made in the horizontal welding
position (fig. 7-15, view C.)
Whether large or small, simple or complex, the
manufacture of any object requires careful planning.
This is especially true when welding is employed to
join parts into an integrated whole. One of the first
decisions to be made regarding welding is the
welding process to be used—that is, which of the
processes is most applicable. But this is only the
An important part of the welding procedure is
refers to the details pertaining to the materials,
methods, and practices used to make a particular
When the longitudinal sequence is used to
produce a continuous weld, you will normally use
either the backstep sequence or the wandering
sequence. The backstep and the wandering
sequences are illustrated in figure 7-16.
joint in the weldment. Included in the joint welding
procedure is the DEPOSITION SEQUENCE. This
term refers to the order in which the weld metal in
a given joint is to be deposited. Do not confuse the
deposition sequence with a weld sequence; weld
sequences will be discussed shortly. The deposition
sequence may call for an intermittent weld or a
continuous weld.
In the BACKSTEP SEQUENCE, as shown in
view A of figure 7-16, the weld does not begin at
the end of the joint. Furthermore, the parts or
increments of the weld are deposited in a direction
opposite to that in which the entire joint is made.
Increment length is usually specified. If it is not,
you can determine the proper weld increment length
by the following procedure.
There are two types of INTERMITTENT
WELDS. Both are fillet welds in which weld
continuity is broken by unwelded spaces. The chain
intermittent weld is illustrated in view B of figure
7-3, and the staggered intermittent in view C of
figure 7-3. In chain intermittent welding, the
increments or parts of the weld are approximately
opposite each other. In staggered intermittent
welding, the weld increments are staggered with
respect to each other on opposite sides of a tee
Select an electrode of the proper type and
diameter. Then, using the same methods that will
be used in welding the joint, run an uninterrupted
bead with one electrode on a piece of scrap metal.
The length of the practice bead is the proper length
for the increment. Thus, if your practice bead is 6
inches long, the first increment is started 6 inches
from the edge of the plate. Successive increments
would start 6 inches away from the previous weld
increment. The backstep sequence is sometimes
called a step-back sequence.
A CONTINUOUS WELD is one in which the
completed joint contains weld metal throughout. In
other words, there are no unwelded portions in the
joint as in an intermittent weld. The continuous
weld is made by one of two main weld sequences,
either the continuous sequence or the longitudinal
view B of figure 7-16, combines some of the features
of both the continuous and the backstep sequences.
In this sequence, weld increments are deposited in
the same direction as the weld joint proper, as in a
continuous sequence. However, as the illustration
indicates, the order in which the weld increments
are deposited is not progressive along the joint.
Instead, gaps equal in length to that of the
A continuous sequence has a slightly different
meaning than does a continuous weld. In a
CONTINUOUS SEQUENCE, welding begins at
one end of the joint and proceeds continuously to
the other. The continuous sequence is the least
complex of all the sequences.
However, a
continuous weld may be produced by a welding
sequence other than the continuous sequence.
result is a continuous weld, but the weld is not made
by proceeding continuously from one end of the
joint to the other. Here different parts of a joint
are made at different times. The longitudinal
sequence specifies the order in which the various
increments of the continuous weld are to be made
with respect to the entire length of the joint. The
longitudinal sequence is completed by one of eight
standard sequences, which includes the backstep, the
wandering, the buildup, the block, the cascade, the
progressive block, the wandering block, and the
selective block. These sequences are used in
welding to minimize distortion by controlling
expansion and contraction.
Figure 7-16.—(A) Backstep sequence; (B) Wandering
deposit. The result of a pass is a weld bead.) The
sequences we will consider next consist of
multiple-pass layer welds.
A LAYER consists of two or more weld beads.
Figure 7-17 shows the use of multiple passes and
layers in making a groove weld. The number of
layers required to complete the weld is determined
by the thickness of the metal being welded and the
diameter of the welding rod being used.
Figure 7-17.—Multiple-pass layers.
Figure 7-18 illustrates block sequence, buildup
sequence, and cascade sequence. Note that all of
these sequences involve longitudinal sequence and
multiple passes and layers. The BLOCK
SEQUENCE, shown in view A of figure 7-18, is a
longitudinal sequence having a specified buildup
order. Individual sections or blocks of the
continuous joint are partially or completely welded
in an order somewhat like that of a backstep or
wandering sequence before intervening sections are
deposited. The term BUILDUP SEQUENCE
refers to the order in which the weld beads of a
multiple-pass weld are deposited with respect to the
cross section of the joint. Thus, a buildup sequence
is a part of any joint that requires layers of filler
metal deposits to make the weld. View B of figure
7-18 shows a buildup sequence. The CASCADE
SEQUENCE, shown in view C of figure 7-18, is a
variation of the block sequence. It has a specified
buildup order, but the weld beads are deposited in
overlapping layers.
increment itself are left along the joint. Once the
length of the joint has been welded in this manner,
the welder fills the gaps, thus producing a
continuous weld. The order in which the parts of
the weld are made may differ from that indicated in
view B of figure 7-16. Another order, such as
6-7-5-3-l-4-2, might be equally satisfactory. For this
reason, the wandering sequence is often called the
random or skip sequence. No matter which order
is selected, the pattern must be predetermined.
Increment length is determined in the way described
for the backstep sequence. It is a good idea to lay
out the joint increment lengths and number each
portion according to the chronological order in
which it is to be welded.
Thus far, we have considered only those
sequences in which a single pass or weld bead is
involved. (A PASS is a single progression of a
welding operation along a joint or weld increment
Figure 7-18.—Block, buildup, and cascade sequences.
There are several other variations of the block
sequence. In the PROGRESSIVE BLOCK
sequence, successive individual blocks of the
continuous weld are completed progressively along
the joint from one end to the other or from the
center of the joint toward either end. Another
variation is the WANDERING BLOCK. In this
sequence, successive blocks are completed at
random after several starting blocks have been
completed. Still another variation is the
successive blocks are completed in a certain order
so that a predetermined stress pattern is created
within the joint.
Figure 7-20.—Visible weld defects: spatter, overlap, and
welding and that do not form part of the weld.
When spatter occurs, small balls of metal are stuck
to the surface of the base metal along the line of
weld. OVERLAP is a protrusion of the weld metal
beyond the bond at the toe of the weld. An
UNDERCUT is a groove melted into the base
metal adjacent to the toe and not filled by weld
metal. Both overlap and undercut are more serious
than spatter, since either may seriously impair the
strength of the weld. Overlap and undercut indicate
that something is wrong with the welding techniques
being employed or that something is wrong with the
adjustment of the equipment.
Weld defects, like the welds themselves, must be
described in standard terms. Common weld defects
that you should be familiar with include incomplete
fusion, inadequate joint and root penetration,
spatter, overlap, undercut, root cracks, toe cracks,
crater cracks, underbead cracks, voids, and
Every welding design assumes that the specified
extent of fusion and penetration will be obtained
throughout the length of the joint. Welds such as
those shown in figure 7-19 would be classified as
defective because of incomplete fusion and lack of
Several kinds of cracks are classified as weld
defects. Uneven expansion and contraction is
usually the basic cause of cracks whether they are in
the weld metal itself or in the adjacent heat-affected
zone. One fairly common kind of crack is the
CRATER CRACK. This occurs in the crater or
depression at the termination of a weld bead in gas
or arc welding.
Inadequate joint and root penetration is cause
for rejection of a weld even if it is sound in all other
respects. The strength required in a weldment is
achieved only when the specified joint and root
penetration is achieved.
Two other types of cracks are shown in figure
7-21. TOE CRACKS occur in the base metal, at
Some visible weld defects are illustrated in
figure 7-20. SPATTER is the term used to describe
metal particles or globules that are expelled during
Figure 7-19.—Examples of incomplete fusion and lack of
Figure 7-21.—Toe cracks and underbead cracks.
electrodes melt off and are a source of the filler
metal supply.
the toe of the weld. UNDERBEAD CRACKS
occur in the heat-affected zone underneath a bead,
and do not extend to the surface of the metal.
Underbead cracks can be detected either by X ray
or ultrasonic examination.
The welding or brazing of certain materials
require the use of a flux to produce a sound joint.
Fluxes are available as liquids, pastes, and powders.
They have a melting point below that of the base
and filler metals, and they are not incorporated into
the weld. Their primary purpose is to prevent the
formation of oxides on the weld joint before and
during welding operations. Fluxes should never be
used as a substitute for proper cleaning.
ROOT CRACKS are similar to toe cracks
except that they occur at the root of the weld. Root
cracks may be in the weld metal or in the base
VOIDS, also known as GAS POCKETS or
BLOWHOLES, are another type of weld defect.
The term POROSITY is used when there are a
number of voids. Voids occur as the result of gas
being absorbed during the welding and then trapped
as the metal solidifies. The absorbed gas is usually
hydrogen. Improper welding techniques, incorrect
adjustment of equipment, or moisture in electrode
coating may lead to the absorption of gas and the
consequent formation of voids.
The application of fluxes will vary depending
upon the type of welding being done. In silver
brazing, the flux is applied directly to the joint with
a brush. In other brazing operations, the filler
metal is heated slightly and dipped into the flux.
The composition of fluxes is covered by a
number of specifications. No one flux is satisfactory
for all purposes. When the type of flux to be used
is not otherwise specified, consult the NSTM or the
latest NAVSEA instruction for the type of flux to
use for a particular job.
SLAG INCLUSION is the term used to describe
the weld defect in which nonmetallic solid material
is trapped in the weld metal or at the bond between
the weld metal and the base metal. The presence of
slag inclusions breaks up the homogeneity of the
metal, thereby providing a point for the
concentration of stresses. In some cases, the
concentration of stresses thus developed leads to
failure of the joint.
Fluxes are not ordinarily required for
oxyacetylene welding of mild steel and low-alloy
ferrous metals. The oxides of these metals melt at
a low temperature and flow away from the weld
area. However, all brazing and soldering jobs on
both ferrous and nonferrous metals require a flux.
All oxyacetylene welding jobs on cast iron, cast steel,
aluminum, copper, copper-base alloys, nickel,
nickel-base alloys, high-chromium alloys, and
silicon-bronze alloys also require a flux.
The metals that are added during the welding
process are known as filler materials or filler metals.
In welding processes in which a space is left
between the parts to be joined, filler metals provide
the intimacy of contact necessary for coalescence.
Filler materials used in welding processes include
welding rods and electrodes.
Several precautions must be observed when you
are working with fluxes. Unless the base metal is
properly cleaned and the correct flux applied to the
joint, fluxing will hinder rather than aid in making
the joint. Further, the flux must not be overheated
or it will fail to serve its purpose. In addition, fluxes
will also deteriorate if they are kept at brazing
temperatures for too long a time. Nearly all fluxes
give off fumes that may be toxic. For that reason,
fluxes should always be used in a well-ventilated
space. Any welding operation requires adequate
ventilation, whether a flux is used or not.
The term WELDING ROD refers to a filler
metal in wire or rod form. It is used in gas welding
processes and in certain electric welding processes,
such as gas tungsten-arc welding, in which the filler
metal does NOT form a part of the electrical circuit.
The only purpose of a welding rod is to supply filler
metal to the joint.
The term ELECTRODE refers to the metal
that, in electric welding, forms a part of the
electrical circuit. In gas tungsten-arc welding,
Sheet metal (1/8 inch and less in thickness) has
such a large surface area per unit of weight that
heat stresses tend to produce warping or buckling of
the sheet. This and the contraction effect
encountered on long seams are the main points to
be considered in sheet metal welding.
Joint edge preparation and proper spacing
between the edges of the parts are important in any
welding operation. The thickness of the plates and
the joint design determine the amount of edge
preparation required. Sheet metal is easily melted
and does not require special edge preparation. The
faces of the square edges can be butted together
and welded. This type of joint can be used on
sheets up to 1/16 inch thick. For metal thicknesses
from 1/16 to 1/4 inch thick, a slight root opening
between the parts is necessary to obtain complete
penetration if welded from both sides. Plate over
3/16 inch thick and welded from one side requires
beveled edges and a root opening as required by
MIL-STD-22. For oxyacetylene welding on plate
over 1/4 inch thick, the edges are beveled at an
angle of 35° to 45°, making the groove angle from
70° to 90°. These edges can be prepared by flame
cutting, shearing, flame grooving, machining,
chipping, or grinding. In any case, the edge surfaces
should be free of oxides, scale, dirt, grease, or other
foreign matter.
The effect of welding a long seam (over 10 or 12
inches) is to draw the seam together as the weld
progresses. If the edges of the seam are placed in
contact with each other throughout their length
before welding starts, the far ends of the seam will
actually overlap before the weld is completed.
One way of overcoming this effect is illustrated
in figure 7-22. The two pieces to be welded are
placed with an increased allowance at the far end,
and as the welding progresses, the two pieces are
drawn together. This allowance is generally one
metal thickness per foot of seam.
Another method of controlling expansion and
contraction is by the use of chill bars. Heavy pieces
of metal are placed on either side of the weld. They
absorb the heat and keep it from spreading across
the whole surface area. Copper is commonly used
for chill bars because of its ability to absorb heat
rapidly. Welding jigs sometimes use this same
principle to remove heat from the base metal. (See
fig. 7-23.)
Plate from 3/8 to 1/2 inch can be satisfactorily
welded from one side only, but heavier sections
should be welded by preparing the edges from both
sides. Generally, butt joints prepared from both
sides permit easier welding, produce less distortion,
and ensure better qualities in the weld metal in
heavy sections than do joints made from one side
The control of temperature before, during, and
after welding is often a matter of vital importance.
Preheating and postheating are specified for many
welds on many types of metals. Control of interpass
temperature is important in all multipass welds.
Heat causes metals to expand, and cooling
causes them to contract. Uneven heating will,
therefore, cause uneven expansion, or uneven
cooling will cause uneven contraction. Under such
conditions, stresses are set up within the metal.
These forces must be relieved, and unless
precautions are taken, warping or buckling of the
metal takes place. When cooling, if nothing is done
to take up the stress set up by the contraction
forces, further warping may result.
If the
surrounding cool sections of the metal are too heavy
to permit this change in shape, the stresses remain
within the metal itself. Such stresses may cause
cracking while cooling or may remain within the
metal until further force is applied, as when the
piece is put into use.
Figure 7-22.—Allowance for a straight butt weld.
composition and thickness of the metal being
POSTHEATING is done primarily for the
purpose of relieving stresses in the metal after it has
been welded. The temperature, the hold time, and
the cooling rate are specified for each job where
postheating is required. In general, slow cooling is
essential for stress-relieving. If the metal is cooled
rapidly, new stresses will develop and thus defeat
the purpose of the postheating.
Requirements for stress-relieving depend upon
the composition of the metal, the thickness of the
metals to be joined, and the complexity of the
weldment. In some cases, stress-relieving may be
specified for a partly welded joint. Stress relief is
usually required for welded joints that will be
subjected to high pressure. Tables to be used as
guides for temperature control are contained in
Figure 7-23.—Example of the use of jigs and chill bars.
Oxyacetylene or propane torches and electric
induction or resistance coils may be used for
preheating and postheating. Portable electric
heaters are furnished to repair ships, tenders, and
other ships and stations that normally fabricate
items made of carbon molybdenum steel and
chromium-molybdenum steel. The complete unit
consists of control devices mounted on a portable
panel, electrical supply connections, heater cable
leads, and heater coils.
The requirements for fabricating piping by
welding vary according to the class of piping
involved. MIL-STD-278 establishes four classes of
piping: P-1, P-2, P-3, and P-LT.
CLASS P-1 includes all piping used for services
where the pressure exceeds 300 psi or the
temperature exceeds 650°F. It also includes ALL
piping systems used for conveying deadly gases or
liquids and hydrogen peroxide (regardless of the
pressures and temperatures in these systems), except
where such systems are covered by classes P-2 or
P-3. Examples of class P-1 piping include steam
lines, hydraulic systems, steam escape piping below
decks, boiler generating tubes, boiler superheater
and economizer elements, and other
pressure-retaining tubes and piping. Class P-1
piping does NOT include nozzle and root
connections to pressure vessels where such
connections are covered by pressure vessel
PREHEATING is the application of heat to the
base metal before a welding or cutting operation is
performed. Preheating is not required for all welds.
When required, the preheat temperature and the
length of time the temperature must be held (hold
time) is specified in the welding process instruction
being used. The preheat temperature and the hold
time depend upon the chemical composition of the
metal, the thickness of the metal, and to some
degree upon the welding method and the type of
welding rod or electrode used. Some alloys are
more successfully welded without any preheat.
Because of the wide variations in preheat
requirements, you must follow the welding
specifications for each job precisely.
CLASS P-2 includes piping used for services
where the pressure does not exceed 300 psi and the
temperature does not exceed 650°F. It also includes
escape piping above decks. Class P-2 piping does
NOT include piping covered by class P-3.
temperature of the deposited weld metal before the
next pass can be made. The interpass temperature
(minimum or maximum as specified in the welding
process instruction) will vary according to the
CLASS P-3 includes all brazed piping of
unlimited pressure and a maximum temperature of
425°F. Fabrication and inspection of brazed piping
should be according to the requirements of
NAVSHIPS 0900-001-7000.
Specific information pertaining to welding on
the various classes of piping is given in the following
CLASS P-LT includes all piping of design
pressure greater than 50 psi and service temperature
for minus 20°F and below.
The shielded metal-arc and gas tungsten-arc
welding processes must be used for the shipboard
welding of P-1 class piping that is 0.109 inch or
more in wall thickness and for the shop welding of
P-1 piping that is more than 0.083 inch in wall
thickness. At least two layers of weld metal must be
applied around all joints in this piping.
The following general considerations apply to all
pipe welding:
—Whenever possible, weld pipe in the horizontal
rolled position. It is much easier to weld near the
top of the pipe than it is to work through the
overhead and vertical positions. By using the
horizontal rolled position, you get the advantages of
increased speed and the likelihood of a sound weld.
Stress relief heat treatment is generally done
after welding on P-1 class piping. Factors that
determine whether or not stress relief is necessary
include the carbon content of the alloy, the
chromium content, the thickness of the joint, and
the size of the pipe (iron pipe size [ips]). Also,
stress relief is required for some materials in P-l
class piping if preheat and interpass temperatures of
200° to 300°F were not maintained.
—Be sure the pipe is carefully aligned.
—Tack welding is used in practically all pipe
welding. The number of tack welds needed is
determined by the diameter of the pipe. The size of
the tack welds is determined by the wall thickness of
the pipe. For 1/2-inch pipe, two diametrically
opposite tack welds are used. On 12-inch pipe, you
will need six tack welds. Four welds are usually
sufficient for the common pipe sizes. Tack welds
are generally incorporated into the finished weld;
therefore, the material used for tack welding MUST
be the same as the filler metal. Any tack weld that
contains cracks or other defects must be removed by
chipping, grinding, or gouging before the final weld
is made.
All welds in P-l piping must be tested
hydrostatically. Most of these welds must also be
inspected by radiographic, magnetic particle, or
liquid penetrant inspection. Requirements for
welding and testing welds in P-l piping are normally
covered by the applicable welding procedure or
military standard. Use NSTM, chapter 074, volume
1, as a starting document. It will refer you to other
applicable documents, such as MIL-STD-278 for
fabrication and inspection, MIL-STD-271 for
nondestructive test requirements, MIL-SD-22 for
joint design, and numerous military specifications
for material requirements. All of these documents
are a necessary part of welding on P-l piping.
—On circumferential butt welds, provide a weld
buildup of 1/16 to 3/32 inch, depending upon wall
thickness and pipe size.
For more in-depth information on a particular
job, refer to the applicable military standards, or
procedures designated for use by NAVSEA.
—In multipass welding, remove all slag from
each bead before depositing the next bead.
—For some welds, peening is permitted as a
means of correcting distortion and minimizing
residual stresses. However, peening MUST NOT be
done on single bead or single layer welds nor on the
last layers of multiple layer welds.
The manual shielded metal-arc process is used
for the shipboard welding of P-2 class piping that is
0.109 inch or more in wall thickness and for the
shop welding of P-2 piping that is 0.083 inch in wall
thickness. Gas tungsten-arc welding may be used on
P-2 piping that is less than 0.109 inch thick.
Thermal stress relief is required for P-2 class
piping welds in carbon steel and carbon
molybdenum alloy steels that have over 35 percent
All welds in P-2 piping must be inspected during
the hydrostatic test of the piping and must be
radiographed if it is required by the plans or
Figure 7-25.—Basic resistance weld symbols.
In general, the manual shielded metal-arc
process is used for the shipboard welding of P-LT
class piping that is 0.109 inch or more in wall
thickness and for the shop welding of P-LT class
piping that is 0.083 inch in wall thickness.
submarines, all silver-brazed joints 1/2 inch ips and
above must be ultrasonically tested.
The tests and inspections for P-LT class piping
are generally the same as those for P-l class piping.
Use the applicable documents that cover joint
designs, welding procedures, stress-relieving, and
nondestructive tests and inspections for each job as
Special symbols are used on drawings to show
the kinds of welds to be used. These symbols have
been standardized by the American Welding Society
and the Department of Defense. The basic
reference in this field for Navy welders is the
American Welding Society Standard, AWS A2.4-79.
AWS A2.4-79 supersedes AWS A2.0-68, which
formerly was the basic reference for the Navy
welders. Although there is no need for you to
memorize all the welding symbols given in AWS
A2.4-79, you should be familiar with the basic weld
symbols and with the standard location of all eight
elements of a welding symbol.
The requirements for P-3 class piping are
equally as important as those for P-l, P-2, and P-LT
piping. P-3 piping systems are assembled by silver
brazing. Filler materials and fluxes must be selected
on the basis of the metals to be joined.
The fabrication and inspection of all P-3 piping
must be according to NAVSEA 0900-LP-001-7000,
Fabrication and Inspection of Brazed Piping Systems.
After the joint is cooled, all accessible sections of
the joint are to be cleaned to remove any scale or
flux that may be present.
The distinction between a weld symbol and a
welding symbol should be noted. A WELD
SYMBOL is a basic weld symbol used to indicate
the type of weld. Thus, the basic weld symbols
shown in figures 7-24 and 7-25 are weld symbols.
The supplementary weld symbols shown in figure
7-26 are used when necessary in connection with the
basic weld symbols. In figures 7-24, 7-25, and 7-26,
view A, shows the symbols that were listed in AWS
In addition to being hydrostatically tested, all
silver-brazed joints in P-3 class piping 2 inches ips
and over must be ultrasonically tested. On
Figure 7-26.—Supplementary weld symbols.
Figure 7-24.—Basic arc and gas weld symbols.
welding; (2) precautions concerning the operation of
equipment; and (3) precautions related to the safety
of personnel.
A2.0-68. Some of the symbols, but not all, have
been changed by AWS A2.4-79. View B shows the
new symbols for those changed. No figure is shown
in view B for those symbols that were not changed.
You should be aware that some drawings available
may still show the symbols that were changed.
The safety precautions given here are general in
nature and should be supplemented by study of the
precautions given in chapter 1 of this manual and
NSTM, chapter 074, volume 1.
An assembled WELDING SYMBOL consists of
the following eight elements (or as many of these
elements as are required): (1) reference line, (2)
arrow, (3) basic weld symbols, (4) dimensions and
other data, (5) supplementary symbols, (6) finish
symbols, (7) tail, and (8) specification, process, or
other reference. The finish symbols indicate the
method of finish, not the degree of finish. The
letter C is used to indicate finish by chipping, M
indicates machining, and G indicates grinding.
A first consideration for safety in welding is the
location and peculiarities of the space in which the
welding operation is to be performed. Welding and
cutting may be performed ONLY in locations
specifically designated for this purpose, unless
approval of the job and the precautions taken to
eliminate fire and explosion hazards have been
obtained from the proper authority.
The elements of a welding symbol have standard
locations with respect to each other, as shown in
figure 7-27.
Fire and explosion hazards are eliminated by
removing or protecting combustible or explosive
materials or vapors, and by taking the precautions
necessary to prevent a reaccumulation of such
materials. The methods for making a space safe for
welding and the tests used to ensure that a space is
free of fire and explosion hazards are the
responsibility of the gas-free engineer, whose duties
Safety precautions for welding may be
considered as falling into three general categories:
(1) precautions with respect to the location of the
Figure 7-27.—Standard location of elements on a welding symbol.
hour must be provided. When welding is performed
on galvanized metals, brass, bronze, and some other
metals, the ventilation requirements increase by at
least 10 percent. For welding performed in a
confined space, positive steps are necessary to
ensure the elimination of health hazards. In
addition, some conditions, like welding inside a
tank, make it necessary for the welder to wear an
air-line mask.
are described in NSTM, chapter 074, volume 3.
Keep in mind that welding MUST NOT be
performed in any location outside the shop unless
the necessary precautions have been taken and
approval has been obtained. Any compartment,
room, tank, or space adjacent there to which
contains or which has contained flammable or
explosive materials, liquids, or vapors must be made
safe, tested, and proclaimed safe before you can
weld in such a space. These restrictions also apply
to closed drums, tanks, and similar containers.
As a welder, you must consider as unsafe every
closed compartment or poorly ventilated space, all
tanks, cofferdams, voids, and similar spaces, until
the gas-free engineer has inspected the space and
has indicated that adequate precautions have been
taken. When the condition of the space has been
determined, the gas-free engineer posts a tag
describing the condition of the space. The tag
posted includes complete information as to whether
or not the space is safe for persons and whether or
not it is safe for hot work. The information on the
tag is expressed in one of the following ways,
depending on the condition of the space:
When welding is being done, a fire watch must
be posted in the vicinity, particularly when
flammable or explosive materials are exposed. If a
fire hazard exists on both sides of a bulkhead or
deck, fire watches must be stationed on both sides
with appropriate types of fire extinguishers. For
example, if the only combustible material within
range of the sparks or heat from welding or cutting
operations is bitumastic waterproofing, a CO2
extinguisher may be adequate. In a small space with
a very small access opening, however, the operator
might not be able to get out quickly in the event of
fire. The use of CO2 would be dangerous in this
case; the use of water from a 1 1/2-inch waterline or
water pump tank would be preferable. If the
insulation on some electrical equipment is the only
combustible material present, the use of water
would be more dangerous than the fire itself. In
this situation, CO2 would be used. In each case, it
is necessary to consider what kind of fire might
occur and to provide the appropriate equipment to
combat it. The fire watch must remain on station at
least 30 minutes after a job has been completed to
make sure that there is no smoldering fire.
NOT safe for persons—NOT safe for hot
Safe for persons—NOT safe for hot work
Safe for persons—Safe for hot work
INERTED—NOT safe for persons
INSIDE—Safe for persons and hot work OUTSIDE
PRESSED UP (with water or oil)—Safe for
persons and hot work OUTSIDE
Adequate ventilation must be provided in all
spaces in which welding is being done and to
eliminate health hazards such as gases, fumes, and
dust caused by the welding operation. Any welding
operation requires that the operator, helper, or fire
watch wear approved respirators regardless of the
amount of ventilation provided. When welding or
cutting operations are performed on lead-bearing
steels, lead-coated or cadmium-coated metals, or
metal covered with paint containing lead or
cadmium, an air-line mask should be worn even if
the work is done in the open air or in a
well-ventilated space.
The term inerted means that a nonflammable gas
(usually CO2) has been introduced into the space
and that the concentration of the gas is sufficient to
reduce the oxygen content of the space to a level
that will not support combustion. The term pressed
up means that the space has been entirely filled with
water or oil.
When it is necessary for welding or cutting to be
performed in any confined space that has a small
exit, all heavy equipment, such as gas cylinders and
welding generators, must be left on the outside. An
attendant who can observe the welder at all times
must also be stationed on the outside of the space
so that in an emergency the attendant can shut off
the gas or the electric current and provide such
When welding is performed on uncoated ferrous
metals, a minimum space allowance of 10,000 cubic
feet per operator or three complete air changes per
other help as the situation demands. If the welder
must enter the space through a manhole or other
small space, a lifeline and safety belt must be
attached to the welder’s body so that the welder can
be quickly removed in an emergency. This
equipment must be attached in such a way that the
welder’s body cannot be jammed in the small
—Use only approved apparatus that has been
examined and tested for safety.
—Stow all cylinders carefully according to
prescribed stowage procedures. Cylinders should be
stowed in dry, well-ventilated, well-protected places,
away from heat and combustible materials. Do
NOT stow oxygen cylinders in the same
compartment as acetylene or other fuel gas
cylinders. All cylinders should be stowed in an
upright position rather than horizontally. If
acetylene cylinders are not stowed in an upright
position (valves at top), they must not be used until
they have been allowed to stand in an upright
position for at least 2 hours.
The discussion thus far has been primarily
concerned with compartments and tanks that are
part of the ship’s structure. Certain special
precautions should be noted for welding or cutting
on any hollow metal article, whether the work is
performed in or out of a welding shop.
Before allowing any welding or cutting to be
done, be sure that if the hollow metal article has
ever held a flammable substance, it is cleaned and
made safe. Even a trace of flammable material in
a drum, tank, or other hollow article would
constitute a tremendous hazard. A container that
has held a flammable substance may be cleaned with
steam if the substance is easily vaporized. For
removing heavy oils, a strong solution of caustic
soda or a similar chemical is usually used.
Thorough rinsing of the article is necessary. After
a container has been cleaned, it should (if possible)
be filled with water, carbon dioxide, or nitrogen.
This precaution should be taken since it may be
impossible to remove all traces of oil or grease from
the seams or corners of the container.
—Do not allow anyone to tamper with cylinder
safety devices.
—When cylinders are in use, keep them far
enough away from the actual welding or cutting so
they will not be reached by sparks, hot slag, or
—Never place a cylinder in such a position that
it could form part of an electrical circuit.
—Never interchange hoses, regulators, or other
apparatus intended for oxygen with those intended
for acetylene.
—Never attempt to transfer acetylene from one
cylinder to another, to refill an acetylene cylinder,
or to mix any other gas with acetylene.
Hollow metal articles must be vented before
being welded or cut, whether or not they have ever
contained a flammable substance. If they are not
vented, the increase in air pressure that occurs when
heat is applied may be sufficient to cause an
—Keep the valves closed on empty cylinders.
—Do not stand in front of cylinder valves while
opening them.
—When a special wrench is required to open a
cylinder valve, leave the wrench in position on the
valve stem while the cylinder is being used so that
the valve can be closed rapidly in an emergency.
Safety precautions for the operation of welding
equipment vary considerably because of the
different types of equipment involved.
Consequently, only general precautions pertaining to
gas welding and to metal-arc welding are given here.
Further precautions may be found in chapter 1 of
this manual, in the references already mentioned,
and in the technical manuals furnished by the
manufacturers of the equipment.
—Keep oxygen cylinders and fittings away from
oil and grease.1 Even a small amount of oil or
grease may ignite violently, with explosive force, in
the presence of oxygen. NEVER lubricate any part
of an oxygen cylinder, valve, or fitting.
Precautions for the operation of gas welding
equipment include the following:
—Do not drop cylinders. Do not handle them
roughly. Rough handling may cause a cylinder valve
to break off, and the sudden release of gas from a
full cylinder may cause it to take off like a rocket.
—Before starting to work, make sure that the
welding machine frame is grounded, that neither
terminal of the welding generator is bonded to the
frame, and that all electrical connections are
securely made. The ground connection must be
attached firmly to the work, not merely laid loosely
upon it.
—Always open cylinder valves slowly. (Do not
open the acetylene cylinder valve more than 1 1/2
—Close cylinder valves before moving cylinders.
—When using portable machines, take care to
see that the primary supply cable is laid separately
so that it does not become entangled with the
welding supply cable.
—Never attempt to force unmatching or crossed
threads on valve outlets, hose couplings, or torch
valve inlets. The threads on oxygen regulator
outlets, hose couplings, and torch valve inlets are
right-handed; for acetylene, these threads are
left-handed. The threads on acetylene cylinder
valve outlets are right-handed, but have a pitch that
is different from the pitch of the threads on the
oxygen cylinder valve outlets. If the threads do not
match, the connections are mixed.
—When stopping work for any appreciable
length of time, be SURE to de-energize the
equipment. When not in use, the equipment should
be completely disconnected from the source of
—Keep welding cables dry and free of oil or
grease. Keep the cables in good condition, and at
all times take appropriate steps to protect them
from damage. If it is necessary to carry cables some
distance from the machines, run the cables
overhead, if possible, using adequate supporting
—Always use the correct tip or nozzle and the
correct pressure for the particular work involved.
This information should be taken from tables or
worksheets supplied with the equipment.
—Do not allow acetylene or acetylene and
oxygen to accumulate in confined spaces. Such
mixtures are highly explosive.
If it is necessary for a welding operator to work
on platforms, scaffolds, or runways at an elevation
of more than 5 feet, provisions should be made to
prevent falling. This can be accomplished by the
use of a railing or some other equally effective
—Keep a clear space between the cylinders and
the work so that the cylinder valves may be reached
quickly and easily if necessary.
—When lighting the torch, open the acetylene
valve first and ignite the gas while the oxygen valve
is still closed. Do not allow unburned acetylene to
escape and accumulate in small or closed
Helmets or hand shields should be used during
all arc welding or arc cutting operations. Goggles
should also be worn by personnel in the vicinity of
arc welding or cutting operations to protect eyes
from injurious rays from adjacent work and from
flying objects. The goggles may have either clear
glass or colored glass, depending on the amount of
exposure to adjacent welding operations. Helpers
or attendants should be provided with proper eye
—When extinguishing the torch, close the
acetylene valve first and then close the oxygen valve.
—When welding or cutting is stopped for a
period of 15 minutes or more, or when the operator
leaves the area, the equipment must be secured.
Precautions for the operation of metal-arc
welding equipment include the following:
Goggles or other suitable protection should be
used during all gas welding or oxygen cutting
—Use only approved welding equipment, and be
sure that it is in good condition.
The specifications for protectors are as follows:
glasses should be provided to protect each helmet,
hand shield, or goggle lens.
1. Helmets and hand shields should be made of
a material that is an insulator for heat and
electricity. Helmets, shields, and goggles must be
fire retardant and must be capable of withstanding
11. Table 7-1 is a guide for the selection of the
proper shade number. These recommendations may
be varied to suit the individual’s needs. The shade
numbers in the following list will help you select the
proper lens to use.
2. Helmets and hand shields of federal
specification GGG-H-21 1 should be arranged to
accommodate and securely hold window lenses
having the specified dimensions, with cover glass,
and designed to permit easy removal of lenses.
Absorptive lenses must be mounted in helmets so
they are not less than 2 inches from the eyes.
a. Shade No. 4, in any type goggle, may be
used for stray light from nearby cutting and welding
operations and for light electric spot welding.
b. Shade No. 5 filter lenses are usually
sufficient for light gas cutting and welding.
3. Goggles designated as style 1 have a rigid
nonadjustable bridge (or adjustable metallic bridge)
without side shields.
c. Shade No. 6 filter lenses are usually
sufficient for gas cutting, medium gas welding, and
arc welding up to 30 amperes.
4. Goggles designated as style 2 have a rigid
nonadjustable bridge (or adjustable metallic bridge)
with side shields.
d. Shade No. 8 filter lenses are usually
sufficient for heavy gas welding and for arc welding
and cutting exceeding 30 but not exceeding 75
5. Goggles designated as style 3 have flexibly
connected lens containers shaped to conform to the
configuration of the face.
e. Shade No. 10 filter lenses should be used
for arc cutting and welding exceeding 75 but not
exceeding 200 amperes.
6. Lens containers must be suitable to firmly
hold lenses of the correct dimensions.
7. Goggles of style 2 should be provided with
side shields of metal, leather, or other durable
asbestos-free material. The material should also be
pliable to permit adjusting the shield to the contour
of the face. If side shields are of metal, they should
be of wire mesh or of perforated sheet having
openings not larger than 0.394 inch.
f. Shade No. 12 filter lenses should be used
for arc cutting and welding exceeding 200 but not
exceeding 400 amperes.
g. Shade No. 14 filter lenses should be used
for arc cutting and welding exceeding 400 amperes.
A variety of special clothing is available to
protect the body during cutting and welding
operations. The protective clothing to be worn will
vary with the size, location, and nature of the work
to be performed. During ANY welding or cutting
operation, you should wear flameproof gauntlets at
all times. For gas welding and cutting, a five-finger
glove is generally used. For electric-arc welding, a
gauntlet-type mitt is recommended. Gauntlets
protect the hands from both heat and metal spatter.
The one-finger mitt designed for electric-arcwelding
has an advantage over the glove because it reduces
the danger of weld spatter and sparks lodging
between the fingers. It also reduces the chafing of
fingers, which sometimes occurs when five-finger
gloves are used for electric-arc welding.
8. Goggles of style 3 should consist of eyecups
and should be shaped to fit the configuration of the
face. They must have adequate ventilation to
prevent fogging.
9. Lenses for helmet and hand shield windows
should have a height of 2 inches (50.8 mm) and a
width of 4.25 inches (108 mm) where one window is
10. Lenses for goggles should have dimensions
not less than 1.5 inches (38 mm) in the vertical
direction and 1.75 inches (44.5 mm) in the
horizontal direction. It is recommended that
circular lenses not involving optical correction be a
uniform diameter of 1.97 inches (50 mm). Cover
Table 7-1.—Eye Protection Shade Guidelines
Shade Numbers
Welding Operations
Shielded Metal-Arc Welding—l/16, 3/32, 1/8, 5/32-inch
Inert-Gas Metal-Arc Welding—(Nonferrous) 1/16, 3/32, 1/8, 5/32-inch electrodes
Inert-Gas Metal-Arc Welding—(Ferrous) 1/16, 3/32, 1/8, 5/32-inch electrodes
Shielded Metal-Arc Welding—3/16, 7/32, 1/4-inch electrodes
Shielded Metal-Arc Welding—5/16, 3/8-inch electrodes
Arc-Air Cutting and Gouging
Torch Brazing
Light Cutting, up to 1 inch
Medium Cutting, 1 inch to 6 inches
Heavy Cutting, 6 inches and over
Gas Welding (Light), up to 1/8-inch
Gas Welding (Medium), 1/8-inch to 1/2-inch
Gas Welding (Heavy), 1/2-inch and over
Some light gas welding and cutting jobs require
no special protective clothing other than gauntlets
and goggles if the regular work clothing is worn
correctly. Sleeves must be rolled down, collar and
cuffs buttoned, and pockets that are not protected
by button-down flaps must be eliminated from the
front of work clothing. Trouser cuffs must not be
turned up on the outside. All other clothing must
be free of oil and grease. High-top or safety shoes
should be worn, and low-cut shoes with unprotected
tops should NOT be worn. Wearing clothing in the
manner described decreases the probability that
sparks will lodge in folds of cloth such as rolled-up
sleeves and cuffs, pockets, or the shirt collar.
welding operations at floor or bench level. Capes
and sleeves are particularly suitable for overhead
welding because the cape protects the back of the
neck, top of the shoulders, and upper part of the
back and chest. Use of the bib in combination with
the cape and sleeves gives added protection to the
chest and abdomen in jobs where protection for the
lower part of the back is not required. The jacket
should be worn only when complete all-around
protection for the upper part of the body is needed,
such as when several welders are working near each
other. Aprons and overalls provide protection to
the legs and therefore are suitable for welding
operations on the deck or floor.
During medium and heavy welding, specially
designed flameproof clothing made of leather, or
other suitable material, may be required. A wide
choice of protective clothing is available so that you
can select the type required for any particular
welding or cutting job.
During overhead welding operations, leather
caps should be worn under helmets to prevent head
burns. Where the welder may be exposed to sharp
or heavy falling objects, hard hats or head
protectors should be attached in such a way as to
form a part of the welding helmet. For very heavy
work, fire-resistant leggings or high boots should be
worn. Shoes or boots having exposed nail heads or
rivets should not be worn. Oilskins or plastic
clothing must not be worn while welding or cutting.
This clothing consists of aprons, sleeves, a
combination of sleeves and bib, jackets, and overalls.
Sleeves provide satisfactory protection for light
If leather protective clothing is not available,
woolen garments rather than cotton garments
should be worn. Wood does not ignite as readily as
cotton, and it affords greater protection from
changes in temperature. Cotton clothing, if it must
be used, should be chemically treated to reduce its
flammability. Synthetic fabrics should not be worn.
A number of nondestructive techniques are used
to determine the quality of welds and welded
structures. Nondestructive tests and inspections
include visual examination, magnetic particle
inspection, liquid penetrant inspection, radiographic
inspection, and ultrasonic tests. Some of these
techniques are widely used throughout the Navy,
and others are used only at large production or
repair activities. These tests will be described in
chapter 11 of this training manual.
Report all injuries to the medical department as
soon as possible. Even a slight burn or scratch
should be treated promptly to prevent infection.
Eye burns should be treated IMMEDIATELY. All
eye burns should be seen as soon as possible by
medical personnel.
Prior to being tested by any other nondestructive
test, all welds must pass a visual examination.
Visual inspection of welds is useful for detecting
undercutting, large cracks, inaccurate dimensions,
and other obvious defects. However, there are
many serious defects that cannot be detected by
visual inspection, even by an experienced inspector.
Visual examination of welds is NOT adequate for
determining the internal soundness of welds or for
detecting very small surface defects.
To keep abreast of changes in the field of
welding, it is essential that you be familiar with a
number of sources of information. There are
numerous Navy and commercial publications
pertaining to welding. Some of these publications
have already been mentioned earlier in this chapter.
In the field of welding, as in so many other fields,
official publications are constantly under revision;
therefore, it is important to make an effort to keep
up with the latest changes as they are issued.
The basic naval reference on welding and allied
processes is NSTM, chapter 074, volume 1.
This chapter has covered several areas of basic
welding. You now have the basic knowledge of the
welding processes, basic sequences, and the
positions of welding. You were given the basic
information on joints, welds, weld symbols, welding
symbols, weld defects, and filler metals. With the
knowledge gained from this chapter, you are on
your way to learning to become a good, safe, and
conscientious welder. Safety can never be stressed
All welded piping must be subjected to
hydrostatic tests to prove the tightness and the
strength of the joints. Test pressures are usually
included in the instructions or specifications for the
welding. If test pressures are not specified, the
hydrostatic test is normally performed at 135
percent of the maximum working pressure.
Upon completion of this chapter; you will be able to perform the following:
Describe the equipment used in oxyacetylene welding and the proper procedures for setup and safe operation of the equipment.
State the principles of oxyacetylene cutting.
Identify the parts of a cutting torch and the function of each part, and describe
some of the special cutting techniques.
Identify the safety precautions you should follow when performing cutting
Describe the different techniques of oxyacetylene welding and the safety
precautions you should follow.
lengths of hose with fittings, a welding torch with tips,
and either a cutting attachment or a separate cutting
torch. Accessories include a friction igniter to light the
torch, an apparatus wrench to fit the various
connections on the regulators, the cylinders, and the
torches; goggles with filter lenses for eye protection;
and gloves for protection of the hands. Flame-resistant
clothing is worn when necessary.
This chapter deals with oxyacetylene cutting and
welding processes, and identifies the equipment and
the operation of the equipment used in oxyacetylene
Oxyacetylene cutting is a method of cutting metal
by using heat and a jet of pure oxygen to produce a
chemical reaction known as oxidation. The results
obtained by using the oxyacetylene cutting method
will range from a ragged, inaccurate edge to a smooth
edge. The material being cut, the cutting method used,
and the skill of the operator are among the factors that
determine the final results.
The major components of a typical portable
oxyacetylene outfit are shown in figure 8-1. Figure 8-2
illustrates a stationary acetylene cylinder bank of a
type used at some activities.
Oxyacetylene welding is a nonpressure process in
which coalescence is produced by heat from an
oxyacetylene flame formed by the combustion of
oxygen and acetylene. The two gases are mixed to
correct proportions in a torch. The torch can be
adjusted to give various types of flame.
Acetylene (chemical formula C2H2) is a fuel gas
made up of carbon and hydrogen. When burned with
oxygen, acetylene produces a very hot flame, having a
temperature between 5700°F and 6300°F. Acetylene
gas is colorless, but has a distinct, easily recognized
odor. The acetylene used on board ship is taken from
compressed gas cylinders. The cylinder is filled with
balsa wood, charcoal, finely shredded asbestos, corn
pith, portland cement, or infusorial earth (an absorbent
material composed of decayed organic matter). These
porous filler materials are used to decrease the size of
Oxyacetylene equipment consists of a cylinder of
acetylene, a cylinder of oxygen, two regulators, two
Figure 8-1.—A portable oxyacetylene outfit.
the open spaces in the cylinder and thus reduce the
danger of explosion. At approximately 29 psi (pounds
per square inch), pure acetylene can be exploded by
nothing more than a slight shock; dissolved in acetone,
however, and stored in cylinders that are filled with
porous material, acetylene can be compressed safely
into cylinders at pressures up to 250 psi. An acetylene
cylinder is shown in figure 8-3. The acetylene cylinder
must be in the vertical position a minimum of 2 hours
before use to allow the porous filler material to settle
and to prevent it from being drawn into the hose,
gauges, and torch.
Line valve
Release valve
Filler plug
Header pipe
F. Flash arrester chamber
G. Escape pipe
H. Cylinder connection pipe
J. Check valve and drain plug
K. Acetylene cylinders
Figure 8-2.—Stationary acetylene cylinder bank.
MAPP (methylacetylene-propadiene) gas is an allpurpose industrial fuel that has the high flame temperature of acetylene and the handling characteristics of
propane. Being a liquid, MAPP gas is obtained by the
pound rather than by the cubic foot, as with acetylene.
One 70-pound (31.5-kg) cylinder of MAPP gas will do
the work of more than 6 1/2, 225-cubic foot acetylene
cylinders. This is a ratio of 70 pounds of MAPP gas to
1,500 cubic feet of acetylene.
The total weight for the 70-pound (31.5-kg)
MAPP cylinder, which is the same physical size as a
Figure 8-3.—Acetylene cylinder.
However, a MAPP gas leak is easy to detect and can be
repaired before it becomes dangerous.
MAPP toxicity is rated “very slight,” but high
concentrations (5,000 ppm) may have an anesthetic
effect. Local eye or skin contact with MAPP gas vapor
causes no adverse effect. However, the liquid fuel will
cause dangerous frostlike burns due to the temperature
at which MAPP gas must be stored.
225-cubic foot acetylene cylinder, is 120 pounds (54.0
kg) when full.
MAPP cylinders contain only liquid fuel. There is
no cylinder packing of acetone to impair fuel withdrawal. For heavy-use situations, a MAPP cylinder
will deliver more than twice as much gas as an acetylene cylinder and for longer periods of time. The entire
contents of a MAPP cylinder can be used, as there is
no acetone that could be drawn into the regulators or
torch. As the gas bums with oxygen, it produces a
flame temperature of 5300°F (2950°C) and will equal
or exceed the performance of acetylene for cutting,
heating, and brazing due to its superior heat transfer
Oxygen is a colorless, tasteless, odorless gas that is
slightly heavier than air. Oxygen will not bum by itself,
but it will support combustion when combined with
other gases. Extreme care must be taken to ensure that
compressed oxygen does not become contaminated with
hydrogen or hydrocarbon gases or liquids, unless the
oxygen is controlled by such means as the mixing chamber of a torch. A highly explosive mixture will be formed
if uncontrolled compressed oxygen becomes contaminated. Oxygen should NEVER come in contact with oil
or grease.
Oxygen cylinders are supplied in several sizes.
The size most commonly used aboard ship is 9 1/8
inches in diameter, weighs about 145 pounds, and has
a capacity of 200 cubic feet. At 70°F, the gas is under
a pressure of 1800 psi.
MAPP is nonsensitive to shock and nonflammable
in the absence of oxygen. There is no chance of an
explosion if a cylinder is bumped, jarred, or dropped.
The cylinders may be stored or transported in any
position with no danger of an explosive air pocket
being formed.
The characteristic odor, while harmless, gives
warnings of fuel leaks in the equipment long before a
dangerous condition can occur.
MAPP gas is not restricted to a maximum working
pressure of 15 psig, as is acetylene. In jobs requiring
higher pressures and gas flows, MAPP at the full
cylinder pressure of 95 psig at 70°F (21 °C) can be used
The gas pressure in a cylinder must be reduced to a
suitable working pressure before it can be used. This is
done by a regulator or reducing valve. Regulators are
either the single-stage or the double-stage type. Singlestage regulators reduce the pressure of the gas in one
step; two-stage regulators do the same job in two steps
or stages. Less adjustment is generally necessary when
two-stage regulators are used.
Figure 8-4 shows a typical single-stage regulator.
The regulator mechanism consists of a nozzle through
MAPP Gas Safety
Liquified MAPP gas is insensitive to shock. A
MAPP gas cylinder will not detonate when dented,
dropped, hammered, or even incinerated. It may also
be safely used up to full cylinder pressures. The gas
vapors, up to 419°F and 285 psig, will not decompose
when subjected to an energy source in the absence of
oxygen. The vapor also is stable up to 600°F and 1,100
psig when exposed to an 825°F probe. The explosive
limits of MAPP gas are 3.4 percent to 10.8 percent in
air, or 2.5 percent to 80 percent in oxygen. As you can
see, these limits are very narrow in comparison with
that of acetylene.
MAPP gas has a highly detectable odor. The smell
is detectable at 100 ppm, or at a concentration 1/340th
of its lower explosive limit.
Small fuel-gas systems may leak 1 or 1 1/2 pounds
of fuel or more in an 8-hour shift. Fuel-gas leaks are
often difficult to find, and many times go unnoticed.
Figure 8-4.—Single-stage regulator.
which the high-pressure gases pass, a valve seat to
close off the nozzle, a diaphragm, and balancing
springs. These are all enclosed in a suitable housing.
Pressure gauges are provided to indicate the pressure
in the cylinder or pipeline (inlet), as well as the
working pressure (outlet). The inlet pressure gauge,
used to record cylinder pressures, is a high-pressure
gauge; the outlet pressure gauge, used to record
working pressures, is a low-pressure gauge. Acetylene
regulators and oxygen regulators are of the same
general type, although those designed for acetylene are
not made to withstand such high pressures as are those
designed for use with oxygen cylinders.
In the regulator, the gas enters the regulator
through the high-pressure inlet connection and passes
through a glass wool filter that removes dust and dirt.
Turning the adjusting screw in, to the right, allows the
gas to pass from the high-pressure chamber to the
low-pressure chamber of the regulator, through the
regulator outlet, and through the hose to the torch.
Turning the adjusting screw to the right INCREASES
the working pressure; turning it to the left
DECREASES the working pressure. The highpressure gauge is graduated in pounds per square inch
from 0 to 3,000 for oxygen and 0 to 400 for acetylene.
This permits reading of the gauge to determine
cylinder pressure. The gauges are graduated to read
correctly at 70°F. The working pressure gauge is
graduated in pounds per square inch from 0 to 30 for
acetylene and from 0 to 50, 0 to 100, 0 to 200, or 0 to
400 for oxygen, depending upon the purpose for which
the regulator is designed. For example, on regulators
designed for heavy cutting, the working pressure
gauge is graduated in pounds per square inch from 0
to 400.
Figure 8-5.—Two-stage regulator.
a handle (body), two tubes (one for oxygen and one for
acetylene), a mixing head, and a tip. Welding tips are
made from a special copper alloy, which dissipates
heat (less than 60 percent copper), and are available in
different sizes to handle a wide range of plate
There are two types of welding torches, the
low-pressure type and the medium-pressure type. In
the low-pressure type, the acetylene pressure is 1 psi
or less. A jet of high-pressure oxygen is necessary to
produce a suction effect, which draws in the required
amount of acetylene. This is accomplished by the
design of the mixer in the torch, which operates on the
injector principle. The welding tips may or may not
have separate injectors designed into the tip. A typical
mixing head for the low-pressure or injector type of
torch is shown in figure 8-6.
The two-stage regulator is similar in principle to
the one-stage regulator, the chief difference being that
the total pressure drop takes place in two steps instead
of one. In the high-pressure stage, the cylinder
pressure is reduced to an intermediate pressure. In the
low-pressure stage, the pressure is reduced from the
intermediate pressure to a working pressure. A
two-stage regulator is shown in figure 8-5.
In the medium-pressure torches, the acetylene is
burned at pressures from 1 to 15 psi. These torches are
made to operate at equal pressures for acetylene and
oxygen. They are sometimes called equal-pressure or
balanced-pressure torches. The medium-pressure
torch is easier to adjust than the low-pressure torch
and, because equal pressures are used, you are less
likely to get a flashback. This means that the flame is
less likely to catch in or back of the mixing chamber.
A typical equal-pressure torch is shown in figure 8-7.
The oxyacetylene welding torch is used to mix
oxygen and acetylene gas in the proper proportions
and to control the volume of these gases burned at the
welding tip. Torches have two needle valves, one for
adjusting the flow of oxygen and the other for
adjusting the flow of acetylene. In addition, they have
Figure 8-6.—Mixing head for a low-pressure torch..
Figure 8-7.—Equal-pressure welding torch.
Welding tips and mixers made by different
manufacturers differ in design. Some makes of torches
are provided with an individual mixing head or mixer
for each size of tip. Other makes have only one mixer
for several tip sizes. Tips come in various types. Some
are one-piece, hard copper tips. Others are two-piece
tips that include an extension tube to make connection
between the tip and the mixing head. When used with
an extension tube, removable tips are made of hard
copper, brass, or bronze. Tip sizes are designated by
numbers, and each manufacturer has its own
arrangement for classifying them. Tips have different
hole diameters.
No matter what type or size tip you select, the tip
must be kept clean. Quite often the orifice becomes
clogged with slag. When this happens, the flame will
not bum properly. Inspect the tip before you use it. If
the passage is obstructed, you can clear it with wire tip
cleaners of the proper diameter or with soft copper
wire. Tips should not be cleaned with machinists’
Except for rod diameter, the welding rod selected
is determined by specification on the basis of the
metals being joined. These specifications may be
either federal or military. This means that they apply
to all federal agencies and the military establishment.
Filler metals are presently covered by one or both of
these specifications.
drills or other sharp instruments. These devices may
enlarge or scratch the tip opening and greatly reduce
the efficiency of the torch tip.
The hose used to make the connection between the
torch and the regulators is strong, nonporous, and
flexible and light enough to make torch movements
easy. It is made to withstand high internal pressures,
and the rubber used in its manufacture is specially
treated to remove sulfur to avoid the danger of
spontaneous combustion. Welding hose is available in
various sizes, depending upon the size of work for
which it is intended. Hose used for light work is 3/16
or 1/4 inch in diameter and has one or two plies of
fabric. For heavy-duty welding and cutting operations,
the hose will have an inside diameter of 1/4 or
5/16 inch and three to five plies of fabric. Single hose
may be ordered in various lengths up to 600 feet on a
spool. Some manufacturers make a double hose that
conforms to the same general specifications. The hoses
used for acetylene and oxygen are the same in grade,
but they differ in color and have different types of
threads on the hose fittings. The oxygen hose is
GREEN and the acetylene hose is RED. For added
protection against mixing of the hoses during
connection, the oxygen hose has right-hand threads
and the acetylene hose has left-hand threads. The
acetylene fittings also have a notch that goes around
the circumference of the fittings for an additional
identification factor.
Many different types of rods are manufactured for
welding ferrous and nonferrous metals. In general,
shipboard welding shops stock only a few basic types
that are suitable for use in all welding positions. These
basic types are known as general-purpose rods. One
such general-purpose rod that will be found in any
Navy welding shop is a rod suitable for oxyacetylene
welding of low-carbon steel. Such a rod is class 1, type
A, as specified in AWS-A5.2-88. The same specification covers welding rods (class II) for use on cast iron.
Rods for gas welding on other common materials
are covered by other specifications. At the time this
manual was written, the following specifications applied: copper-base alloys, MIL-R-19631B; corrosionresisting and heat-resisting steel, MIL-R-5031B, class
5; nickel-base alloys, including Monel, QQ-R-571C;
and nickel-chromium-iron alloys, MIL-T-23227.
The procedure for setting up oxyacetylene
equipment is as follows:
1. Secure the cylinders so that they cannot be
upset. Ensure that the acetylene cylinders have been in
the vertical position a minimum of 2 hours before
removing the protective caps.
2. Crack the cylinder valves slightly to blow out
any dirt that may be in the valves. Close the valves.
Check for grease and oil on or near the valves and
fittings of the cylinders. Wipe the connections with a
clean cloth.
The term welding rod refers to a filler metal, in
wire or rod form, used in gas welding and brazing
processes and in certain electric welding processes
(tungsten inert-gas) in which the filler metal is not a
part of the electric circuit. A welding rod serves only
one purpose—it supplies filler metal to the joint.
As a rule, rods are uncoated except for a thin film
resulting from the manufacturing process. Welding
rods for steel are often copper-coated to protect them
from corrosion during storage. Most rods are furnished
in 36-inch lengths and a wide variety of diameters,
ranging from 1/32 to 3/8 inch. Rods for welding cast
iron vary from 12 to 24 inches in length and are
frequently square rather than round in cross section.
The rod diameter selected for a given job is governed
by the thickness of the metals being joined.
Never crack gas cylinder valves toward
an individual and always wear safety glasses.
3. Connect the acetylene pressure regulator to the
acetylene cylinder and the oxygen pressure regulator to
the oxygen cylinder. Using the appropriate wrench
provided with the equipment, tighten the connecting
nuts enough to prevent leakage. Never use vice grips,
pliers, adjustable wrenches, and so on to open or close
gas cylinder valves or to tighten equipment fittings. You
will only ruin the valve stem and damage equipment,
making it impossible to open or close the equipment in
an emergency.
10. Adjust the working pressures. A standard,
working pressure of 20 to 25 psi oxygen and 5 to 7 psi
acetylene is recommended. The acetylene pressure is
adjusted by turning the regulator screw to the right until
the desired pressure is attained. (Due to the instability
of acetylene at high pressures, you should never exceed
15 psig on the regulator gauge.)
4. Connect the red hose to the acetylene regulator
and the green hose to the oxygen regulator. Tighten the
connecting nuts enough to prevent leakage.
11. Light and adjust the welding flame. Open the
oxygen needle valve a very slight amount and then the
acetylene needle valve considerably more than the
oxygen needle valve. Light the flame with a friction
igniter. Make sure that the flame path is pointed in a safe
direction and that your hands are not in front of the torch
tip. Adjust the oxygen and acetylene needle valves as
necessary to get a proper flame.
5. Back off on the regulator screws, and then open
the cylinder valves slowly. Open the acetylene valve
one-fourth to one-half turn. This will allow an adequate
flow of acetylene, and the valve can be turned off
quickly in an emergency. (NEVER open the acetylene
cylinder valve more than 1 1/2 turns.) The oxygen
cylinder valve should be opened all the way to eliminate
leakage around the stem. (Oxygen valves are
double-seated or have diaphragms to prevent leakage
when they are open.) Read the high-pressure gauge to
check the pressure of each cylinder.
A pure acetylene flame is long and bushy and has
a yellowish color, as shown in figure 8-8. It is burned
by the oxygen in the air, which is not sufficient to bum
the acetylene completely; therefore, the flame is
smoky, producing a soot of fine, unburned carbon. The
pure acetylene flame is unsuitable for welding. When
the oxygen valve is opened, the mixed gases burn in
contact with the tip face. The flame changes to a
bluish-white color and forms a bright inner cone
surrounded by an outer flame envelope. The inner cone
develops the high temperature required for welding.
6. Blow out the oxygen hose by turning the
regulator screw in and then back out again. If it is
necessary to blow out the acetylene hose, do it ONLY in
a well-ventilated place that is free from sparks, flames,
or other possible sources of ignition.
7. Connect the hose to the torch. The torch hose
connections should be marked with a small “ac” or
“acet” for acetylene or “ox” for oxygen stamped on the
connection or the needle valve. Also, to prevent you
from cross-connecting hoses or equipment, all acetylene
connections have left-hand threads and all oxygen
connections have right-hand threads.
There are three types of flame commonly used for
welding. These are neutral, reducing or carburizing,
and oxidizing flames. (See fig. 8-8.) The NEUTRAL
flame is produced by burning one part of oxygen to one
part of acetylene. Together with the oxygen in the air,
it produces complete combustion of the acetylene. The
luminous white cone is well defined and there is no
greenish tinge of acetylene at its tip, nor is there an
excess of oxygen. The welding flame should always
be adjusted to neutral before either the oxidizing or
carburizing flame mixture is set. A neutral flame is
obtained by gradually opening the oxygen valve to
shorten the acetylene flame until a clearly defined
inner luminous cone is visible. The neutral flame is
used for most welding and for the preheating flames
during cutting operations. The temperature at the tip
of the inner cone is about 5900°F, while at the
extreme-end of the outer cone it is only about 2300°F.
This gives you a chance to exercise some temperature
control by moving the torch closer or farther from the
work. When steel is welded with this flame, the puddle
8. Test all oxyaceteylene connections for leaks.
There are several ways to test oxyacetylene connections
for leaks after the system has been pressurized. The
preferred method is to coat all connections with a soapy
water solution and check for the formation of small
bubbles. The formation of small bubbles at the
connection indicates leaking gas and you should
retighten the connection as needed. Another way to
check fittings for leakage is to secure the system at the
cylinder by closing the cylinder valve and check for a
pressure drop on the regulator gauges. Any drop in
pressure, on the gauges, indicates a loose connection and
you should retighten all connections.
9. Adjust the tip. Screw the tip into the mixing
head and assemble in the torch body. Tighten by hand
and adjust to the proper angle. Secure this adjustment
by tightening with the wrench provided with the torch.
Figure 8-8.—Characteristics of the oxyacetylene flame.
flame. The carburizing flame bums with a temperature
of about 5700°F at the tip of the inner cone. When it is
used for welding steel, the metal boils and is not clear.
A carburizing flame is best for welding high-carbon
steels, for hard-surfacing, and for welding nonferrous
alloys such as Monel.
of molten metal is quiet and clear, and the metal flows
without boiling, foaming, or sparking.
produced by burning an excess of acetylene. You will
be able to recognize it by the feather at the tip of the
inner cone. At the end of the inner cone, this feathery
tip has a greenish color. The degree of carburization
can be judged from the length of the feather. For most
welding operations, the length of the feather should be
about twice the length of the inner cone. You can
always recognize the carburizing flame by its three
distinct colors. These are the bluish-white inner cone,
a white intermediate cone, and the light-blue outer
The OXIDIZING flame is produced by burning an
excess of oxygen. The oxidizing flame bums with a
temperature of about 6300°F at the tip of the inner
cone. You can identify this flame by the short outer
flame and the small, white, inner cone. It takes about
two parts of oxygen to one part of acetylene to produce
this flame, and you will find that the adjustment for the
oxidizing flame is a bit more difficult to make than the
adjustment for other flames. To adjust for the
oxidizing flame, first adjust to a neutral flame and then
open the oxygen valve until the inner cone is about
one-tenth of its original length. An oxidizing flame
makes a hissing sound, and the inner cone is somewhat
pointed and purplish in color at the tip. The oxidizing
flame has a limited use and is harmful to many metals.
When it is applied to steel, the oxidizing flame causes
the molten metal to foam and give off sparks. This
means that the extra amount of oxygen is combining
with the steel, causing the metal to burn. However, the
oxidizing flame does have its uses. A slightly oxidizing
flame is used to braze weld steel and cast iron, and a
stronger oxidizing flame is used for fusion welding of
brass and bronze. You will have to determine the
amount of excess oxygen to use in this type of flame
adjustment by watching the molten metal.
regulators and the torch from the system, double check
the cylinder valves to make sure they are closed
securely, and reinstall the cylinder valve protection
Oxyacetylene cutting is the most commonly used
method of cutting ferrous metals by the application of
heat. The principle of oxyacetylene cutting is simple.
The metal is heated to its ignition temperature by
oxyacetylene flames. Then a jet of pure oxygen is
directed at the hot metal, and a chemical reaction
known as OXIDATION takes place. Oxidation is a
familiar chemical reaction. When it occurs rapidly, it
is called COMBUSTION or BURNING; when it
occurs slowly, it is called RUSTING. When metal is
being cut by the oxyacetylene torch method, the
oxidation of the metal is extremely rapid-in short, the
metal actually burns. The heat liberated by the burning
of the iron or steel melts the iron oxide formed by the
chemical reaction, and it also heats the pure iron or
steel. The molten material runs off as slag, exposing
more iron or steel to the oxygen jet.
To extinguish the oxyacetylene flame and to
secure equipment after completing a job, or when work
is to be interrupted temporarily, the following steps
should be taken:
1. Close the acetylene needle valve first; this
extinguishes the flame and prevents a flashback.
(Flashback is discussed later in this chapter.) Then close
the oxygen needle valve.
In oxyacetylene cutting, only that portion of the
metal that is in the direct path of the oxygen jet is
oxidized. Thus, a narrow slit (called a kerf) is formed
in the metal as the cutting progresses. Most of the
material removed from the kerf is in the form of oxides
(products of the oxidation reaction). The remainder of
the material removed from the kerf is pure metal,
which is blown or washed out of the kerf by the force
of the oxygen jet.
2. Close both oxygen and acetylene cylinder
valves. Leave the oxygen and acetylene regulators open
3. Open the acetylene needle valve on the torch and
allow gas in the hose to escape for 5 to 15 seconds. Do
not allow gas to escape into a small or closed
compartment. Close the acetylene needle valve.
Since oxidation of the metal is a vital part of the
oxyacetylene cutting process, this process is not
suitable for metals that do not oxidize readily, such as
copper, brass, stainless steel, and so on. Low-carbon
steels are easily cut by the oxyacetylene cutting
process, but special techniques (described later in this
chapter) are required for the oxyacetylene cutting of
many other metals.
4. Open the oxygen needle valve on the torch.
Allow gas in the hose to escape for 5 to 15 seconds.
Close the valve.
5. Close both oxygen and acetylene cylinder
regulators by backing out the adjusting screws until they
are loose.
The foregoing procedure should be followed
whenever work is interrupted for an indefinite period.
If work is to stop for only a few minutes, securing
cylinder valves and draining the hose is not necessary.
However, for any indefinite work stoppage, the entire
extinguishing and securing procedure should be
followed. For overnight work stoppage in areas other
than the shop, you should always remove the pressure
The walls of the kerf formed by oxyacetylene
cutting should be fairly smooth and parallel. When you
develop skill in handling the torch, you will be able to
hold the cut to within reasonably close tolerances.
Also, you will be able to guide the cut along straight,
curved, or irregular lines, and to cut bevels or other
shapes that require holding the torch at an angle.
available with either a 75-degree or 90-degree cutting
head. The spiral mixer chamber provides excellent
mixing of the oxygen and acetylene to the preheating
The standard cutting torch looks very much like
the oxyacetylene welding torch. The main difference
in the two torches is that the cutting torch has an extra
tube for high-pressure (cutting) oxygen. The flow of
high-pressure oxygen is controlled by a lever valve
assembly on the handle of the cutting torch. A standard
cutting torch is shown in figure 8-9. This torch is of
rugged, trouble-free construction; and it is designed
for operator comfort, and ease and economy of
maintenance and repair if it is damaged. This torch is
1. Tip
2. 90° Head
3. Cutting Oxygen Tube
4. Oxygen Valve Assembly
Some welding torches are furnished with a cutting
attachment that may be fitted to the torch in place of
the welding head (tip). With this type of attachment
(shown in fig. 8-10), the welding torch may be used as
a cutting torch. This type of torch is generally called a
combination torch. High-pressure oxygen is controlled
by a lever on the torch handle.
5. Handle
6. Acetylene Valve Assembly
7. Cutting Oxygen Lever
8. Acetylene Tube
Figure 8-9.—Standard oxyacetylene cutting torch.
Figure 8-10.—Cutting attachment for an oxyacetylene cutting torch.
too often, careless workers or ones not acquainted with
the correct procedures waste both oxygen and fuel gas.
Cutting tips are made of copper or of tellurium-copper alloy. Each manufacturer has cutting tips of different
designs. The orifice arrangements and tip material are
much the same among various manufacturers; however,
the part of the tip that fits into the torch head often differs
in design. Figure 8-11 shows several different orifice
arrangements and their uses.
Just as in welding, you must use the proper size
cutting tip if quality work is to be done. The preheat
flames must furnish just the right amount of heat, and
the oxygen jet orifice must deliver the correct amount
of oxygen at just the right pressure and velocity to
produce a clean cut (kerf). All of this must be done with
a minimum consumption of oxygen and fuel gases. All
Figure 8-11.—Common cutting torch tips and their uses.
Table 8-1.—Ranges of Oxyacetylene Cutting Tips
metal and the larger sizes are used for cutting heavy
metal. Tip sizes are identified by numbers. When
numbers such as 000, 00, 0, 1, 2, 3, 4, and 5 are used
to identify tip sizes, the lower numbers indicate the
smaller tips; for example, a 000 tip is smaller than a
number 1 tip, and a number 1 tip is smaller than a
number 5 tip. Some manufacturers identify cutting tips
by giving the drill size number of the orifices. Large
drill size numbers indicate small orifices; for example,
drill size 64 is smaller than drill size 56. In military
The central opening or orifice in the tip is for the
jet or stream of high-pressure oxygen that does the
cutting. The smaller orifices are for oxyacetylene
flames used for preheating the metal to its ignition
temperature. There are usually four or six of these
preheat orifices in each oxyacetylene cutting tip;
however, some heavy-duty tips have many more
preheat orifices.
Cutting tips are furnished in various sizes. In
general, the smaller sizes are used for cutting thin
Figure 8-12.—Cutting tips in various conditions.
specifications and standards, oxyacetylene cutting tips
are identified by three-part numbers. The first part is
the tip size (0, 1, 2, 3, and so on). The second part is
the drill size number of the orifice for the cutting
oxygen. The third part is the drill size number of the
preheat orifices. For example, the number l-62-64
identifies a number 1 tip with a cutting oxygen orifice
of drill size 62 and preheat orifices of drill size 64.
Table 8-1 gives tip numbers, orifice sizes, and
approximate cutting ranges of various sizes of oxyacetylene cutting tips. Cutting tips from different manufacturers are not interchangeable; when changing tips,
you must match the right tip with the right torch.
The tips and seats are designed and constructed to
produce a good flow of gases, to keep the tips as cool
as possible, and to produce leakproof joints. If the
joints leak, the preheat gases may mix with the cutting
oxygen or they may escape to the atmosphere.
It is very important that the orifices and passages
be kept clean and free of burrs to permit a free gas flow
and a well-shaped flame. Figure 8-12 shows four tips:
one that is repairable, two that need replacing, and one
in good condition. Since it is extremely important that
the sealing surfaces be kept clean and free of scratches
or burrs, the tips should be stored in a container that
cannot scratch the seats, preferably an aluminum or
wood rack.
Figure 8-13.—MAPP gas cutting tips.
faster starts than the SP tips. However, two-piece tips
will not take as much thermal abuse or physical abuse
as will one-piece tips. But in the hands of skilled
welders, they should last just as long as one-piece tips.
MAPP Gas Cutting Tips
Care of Tips
There are four basic types of MAPP gas cutting
tips; two are designed for use with standard pressures
and normal cutting speeds, and two for use with high
pressures and high cutting speeds. Only the standard
pressure tips, types SP (standard pressure) and FS (fine
standard), will be covered here since they are the ones
that HTs will most likely use.
In cutting operations, the stream of cutting oxygen
sometimes will blow slag and molten metal into the
orifices and cause them to become partly clogged.
When this happens, you should clean the orifices
thoroughly before you use the tip again; even a very
small amount of slag or metal in an orifice will
seriously interfere with the cutting operation. The
recommendations of the torch manufacturer should be
followed as to the size of drill or tip cleaner to use for
cleaning the orifices. If you do not have a tip cleaner
or a drill, then you may use a piece of soft copper wire.
Do not use twist drills, nails, or welding rods for
cleaning tips, as these items are likely to enlarge and
distort the orifices.
SP TIP.—The SP tip (fig. 8-13, view A) is a
one-piece standard-pressure tip. It is used for cutting
by hand, especially by welders who are accustomed to
one-piece tips. SP tips are also likely to be used in
situations where MAPP gas is replacing acetylene as
the fuel gas.
FS TIP.—The FS tip (fig. 8-13, view B) is a
two-piece, fine-spline, standard-pressure tip. It is used
for cutting by hand as well as by machine. Welders
accustomed to two-piece cutting tips will use them in
hand cutting, especially in cases where MAPP gas is
replacing natural gas or propane as the fuel gas. The
FS tips will produce heavier preheating flames and
The orifices of the cutting torch tip are cleaned in
the same manner as the single orifice of the welding
torch tip. Remember that the proper technique for
cleaning the tips is to push the cleaner straight in and
out of the orifice; be careful not to turn or twist it.
Occasionally the cleaning of the tips will cause
enlargement and distortion of the orifices even if the
proper tip cleaners are used. If the orifices become
enlarged, you will get shorter and thicker preheating
flames; in addition, the jet of cutting oxygen will
spread rather than leave the torch in the form of a long
thin stream. If the orifices become belled for a very
short distance at the end, it is sometimes possible to
correct this condition by rubbing the tip back and forth
against emery cloth on a flat surface. This wears down
the end of the tip where the orifices have been beveled,
thus bringing the orifices back to their original size.
Obviously, this procedure would not work if the
enlargement is very great or if the belling extends more
than a slight distance into the orifice.
After reconditioning a tip, you may test it by
lighting the torch and observing the preheating flames.
If the flames are too short, the orifices are still partially
blocked. If the flames snap out when the valves are
closed, the orifices are still distorted.
Figure 8-14.—Position of torch tip for starting a cut.
If the tip seat is dirty or scaled so that it does not
fit properly into the torch head, you should heat the tip
to a dull red and quench it in water. This will loosen
the sale and dirt enough so that they can be rubbed off
with a cloth.
If the cut is being started correctly, a shower of
sparks will fall from the opposite side of the work,
indicating that the cut is going all the way through.
Move the cutting torch forward along the line just fast
enough for the cut to continue to penetrate the work
completely. If you have made the cut properly, you
will get a clean, narrow cut that looks somewhat like
one made by sawing. When cutting round bars or
heavy sections, you can save time and gas if you raise
a small burr with a chisel where the cut is to start. This
small raised portion will heat quickly, and cutting can
be started sooner. If you have a cut to start from the
center on some portion of metal other than the edge,
use the following method for starting the cut. Preheat
to a bright red the spot on the surface where the cut is
to start. Tilt the torch at an angle of about 45° from the
perpendicular, in line with the direction of the cut.
Press the cutting oxygen lever very slowly. As the
torch begins to cut, start righting it to a perpendicular
position to the surface of the plate. Continue to right
the position of the torch gradually as it cuts until it is
at 90° to the surface of the plate and is cutting all the
way through. Move it forward along the line of cut as
fast as complete penetration can be accomplished. If
you do not follow this procedure, you are likely to blow
the slag back on the cutting tip, clogging the orifices
or otherwise damaging the equipment. When you have
started a cut, move the torch slowly along the cutting
mark or guide. As you move the torch along, watch the
Before beginning any oxyacetylene cutting operation, be sure you have selected the right size tip for the
job. Follow the manufacturer’s recommendations concerning tip sizes to use for different kinds of work. The
oxygen and acetylene pressures to be used with various
sizes of tips are also given by the manufacturer. Before
fitting a cutting tip into the torch head, inspect the tip
carefully to be sure that it is clean and not distorted,
and that the orifices are not clogged with slag.
Cutting Low-Carbon Steel
To cut low-carbon steel with the oxyacetylene
cutting torch, adjust the preheating flames to neutral.
Hold the torch perpendicular to the work, with the
inner cones of the preheating flames about
one-sixteenth inch above the end of the line to be cut,
as shown in figure 8-14. Hold the torch in this position
until the spot you are heating is a bright red. Introduce
the cutting oxygen by depressing the oxygen lever
slowly but steadily.
Figure 8-15.—Bevel cutting with an oxyacetylene torch.
Figure 8-17.—Cutting pipe with a cutting torch.
cut so you can tell how it is progressing. Make torch
adjustments if necessary. You must move the torch
along at the right speed. If you go too slowly, the
preheating flame will melt the edges along the cut and
may even weld them back together at the top surface.
If you go too fast, the oxygen will not penetrate
completely through the metal, and the cut will be
incomplete. If you must restart or recut your work, do
so on the waste side of your metal. This serves three
purposes. First, it is easier to restart your cut on the
edge of the kerf than in the center. Second, you don’t
leave an unsightly gouge or nick in your finished work
where you restarted your cut. And finally, you don’t
cut your metal too short by recutting the edge.
Beveling Plate
You will frequently have to cut bevels to form
joints for welding. To make a bevel cut of 45° in 1-inch
steel, the flame must actually cut through 1.4 inches of
metal. Consider this when selecting the tip size and gas
working pressures. You will have to use more pressure
and less speed for a bevel cut than for a straight cut.
When you are bevel cutting, adjust the tip so that the
preheating orifices are lined up for efficient preheating. A piece of 1 -inch angle iron, clamped with the
angle up, makes an excellent guide for beveling
straight edges. Pull the torch along the guide as shown
in figure 8-15.
If you are aboard a repair ship or a tender, you may
have a radiograph automatic cutting machine similar
to the one in figure 8-16. This is a motor-driven cutting
machine designed to support the cutting torch and
guide it along the line of cut. It can be set to make
uniformly clean cuts or bevels on steel plate.
Straight-line cutting or beveling is done by guiding the
machine along a straight line on steel tracks. Arcs and
circles are cut by guiding the machine with a radius
rod pivoted about a center point.
Cutting and Beveling Pipe
When you are cutting off a piece of pipe, keep the
torch pointed toward the center line of the pipe. Start
the cut at the top and cut down one side. Then begin at
the top again and cut down the other side, finishing at
the bottom of the pipe. The procedure is shown in
figure 8-17.
Sometimes it is necessary to take T and Y fittings
from pipe. Here the cutting torch is a most valuable
tool. The usual procedure for fabricating pipe fittings
Figure 8-16.—Bevel cutting on a circular path with a
radiograph automatic cutting machine.
An experienced burner can cut and bevel pipe at a
45-degree angle in one operation; however, a person
with little experience may have to do the job in two
steps. The first step is to cut the desired part at a
90-degree angle. The second step is to bevel the edge
of the cut to a 45-degree angle. When employing the
two-step procedure, another line must be marked on
the pipe. This second line follows the contour of the
line traced around the pattern, but it is drawn away
from the original pattern line at a distance equal to the
pipe wall thickness. The first (or 90°) cut in the
two-step procedure is made along the second line. The
second (or 45°) cut is made along the original pattern
line. The two-step procedure is time consuming and
uneconomical in terms of oxygen and acetylene
is to develop a pattern like that shown in figure 8-18,
view A, step 1. After the pattern is developed, it is
wrapped around the pipe as shown in figure 8-18, view
A, step 2. Be sure to leave enough stock so that the
ends will overlap. Trace around the pattern with
soapstone or a scriber. It is a good idea to mark the
outline with a prick punch at about one-fourth-inch
intervals. When the metal is heated during the cutting
procedure, the punch marks will stand out, making it
easier to follow the line of cut. Place the punch marks
so that they will be removed during cutting. If punch
marks are not removed, they provide notches from
which cracking may start.
When you are experienced enough to use the
one-step cutting and beveling procedure, you will find
that it is not complicated. However, both a steady hand
and a great deal of practice are necessary to turn out a
first-class job. The one-step procedure for cutting and
fabricating a T is shown in figure 8-18. View A of
figure 8-18 outlines the step-by-step procedure for
producing the branch; view B shows the steps for
preparing the other section of the T; and view C shows
the assembled T, tack welded and ready for welding.
Figure 8-18, view A, step 3, shows the procedure for
cutting the miter on the branch. The cut is started at the
end of the pipe and worked around until one-half of
one side is cut. The torch is manipulated so that at all
times the tip is at an angle of 45° to the surface of the
pipe along the line of cut. While the tip is at a 45-degree
angle, the torch is moved steadily forward and at the
same time the butt of the torch is swinging upward
through an arc. This torch manipulation is necessary
to keep the cut progressing in the proper direction and
to produce a bevel that will be 45° at all points on the
miter. The second portion of the miter is cut in the same
manner as the first.
The torch manipulation necessary for cutting the
run of the T is shown in steps 3 and 4 in view B of
figure 8-18. Step 3 shows the torch angle for the
starting cut. At step 4, the cut has progressed to the
lowest point on the pipe. Here the angle has been
changed to get around the sharp curve and start the cut
in an upward direction. The completed cut for the run
is shown in step 5 in view B of figure 8-18.
Before the parts of any fabricated fitting are
assembled and tack welded, be sure to clean the fit of
the joint. The bevels must be smooth to allow complete
fusion when the joint is welded.
Figure 8-18.—Fabricating a T fitting.
round spot has been heated to a bright red. Introduce
the cutting oxygen by gradually depressing the oxygen
lever, and at the same time slightly raise the tip away
from the work to keep from blowing slag back onto the
cutting tip. As you start raising the torch and
introducing the cutting oxygen, start rotating the torch
with a spiral motion. This will cause the molten slag
to be blown out of the hole. The hot slag may fly
around, so BE SURE your goggles are well fitted to
your eyes and face, and avoid having your head
directly above the cut.
Piercing Holes
The cutting torch is also a valuable tool for
piercing holes in steel plate. The steps are illustrated
in figure 8-19. Lay the plate out on two firebricks so
that the flame will not hit something else when it bums
through the plate. Hold the torch over the hole location
with the tips of the inner cone of the preheating flames
about one-fourth inch above the surface of the plate.
Continue to hold the torch in this position until a small
If you need a larger hole, outline the edge of the
hole with a piece of chalk, and follow the procedure
given in the previous paragraph. Start the cut from the
hole that you have pierced by moving the preheating
flames to the normal distance and by working to and
following the line that has been drawn on the plate.
Round holes can be made by using a cutting torch with
a radius bar attachment.
Cutting Rivets
When you are required to remove rivets from
plates that are to be disassembled, you will find the
cutting torch a good tool. The cutting procedure is
shown in figure 8-20. Use the preheating flames of the
Figure 8-19.—Piercing a hole with an oxyacetylene cutting
Figure 8-20.—Using a cutting torch to remove the head of a rivet.
A low-velocity cutting tip has a cutting oxygen orifice
with a large diameter. Above this orifice are three
heating orifices. Always place a low-velocity cutting
tip in the torch so that the heating orifices are above
the cutting orifice when the torch is held in the rivet
cutting position. To remove countersunk rivets from a
vertical sheet or plate, use the method shown in figure
8-21 and follow these instructions:
cutting torch to bring the head of the rivet up to the
proper temperature; then introduce the cutting oxygen
by gradually depressing the oxygen lever, and wash
off the rivet head. The remaining portion of the rivet
can then be punched out with a light hammer blow.
The step-by-step procedure follows:
1. Use the size of tip and the oxygen pressure
required for the size and type of rivet you are going to
2. Heat a spot on the head until it is bright red.
1. Hold the torch horizontally and turn it so that the
tip also points horizontally.
3. Move the tip to a position parallel with the
surface of the plate and slowly turn on the cutting
2. Tilt the tip upward about 15° and hold the
preheating flames on a point slightly below the center
of the rivet head.
4. Cut a slot in the rivet head like the screwdriver
slot in a roundhead screw. When the cut nears the plate,
draw the nozzle back at least 1 1/2 inches from the rivet
so that you will not cut through the plate.
3. When you get the area heated to a dull red, move
the torch upward, still keeping the upward tilt, and press
the cutting oxygen lever.
4. Hold the torch steady with the cutting stream
directed at the center of the rivet. As the rivet is cut away,
the angle of the torch should be decreased until the tip
is perpendicular to the sheet or plate and the cutting
stream is directed at the center of the rivet.
5. When you have cut the slot through to the plate,
swing the tip through a small arc. This slices off half of
the rivet head.
6. Then swing the tip in an arc in the other direction
to slice off the other half of the rivet head.
5. When you have cut through the head to the shank
of the rivet, wash away the remainder of the head with
one circular wiping motion. Always move the torch so
that the cutting stream will follow the preheat.
By the time the slot has been cut, the rest of the
rivet head has usually been heated to cutting
temperature. Just before you get through the slot, draw
the torch tip back 1 1/2 inches to allow the cutting
oxygen to scatter slightly. This keeps the torch from
breaking through the layer of scale that is always
present between the rivet head and the plate. It allows
the head of the rivet to be cut off without damaging the
surface of the plate. If you do not draw the tip away,
you may cut through the film of scale and into the plate.
6. The shank may then be removed by a light tap
with a hammer and punch.
Buttonhead rivets may be removed in the same
manner as countersunk rivets with the low-velocity
cutting tip. The process is illustrated step by step in
figure 8-22. Remember that it is important to start
below the center of the rivet head so that molten metal
and slag will not be deposited on the plate.
A low-velocity cutting tip is best for cutting
buttonhead rivets and for removing countersunk rivets.
Figure 8-21.—Cutting a countersunk rivet with a low-velocity cutting tip.
Figure 8-22.—Cutting buttonhead rivets with a low-velocity cutting tip.
Special Cutting Techniques
in the carburizing flame ignites when it combines with
the cutting oxygen deep in the kerf, thus increasing
both the intensity and the distribution of the preheat.
For cutting cast iron, the length of the feather on the
preheating flame should be approximately equal to the
thickness of the cast iron. A slightly less carburizing
flame is used for cutting stainless steel.
Carbon steels containing up to 1.0 percent carbon
are easily cut with the oxyacetylene cutting torch.
Nonferrous metals, however, and ferrous metals such
as cast iron, carbon steels containing more than 1.0
percent carbon, and many alloy steels can be
successfully flame cut only if special techniques are
used. These special techniques include using more
intense and more widely distributed preheat; using
different flame adjustments; introducing iron or
low-carbon steel into the cutting area; varying the
torch movements; and using fluxes.
INTRODUCTION OF IRON OR LOWCARBON STEEL.—Introducing iron or low-carbon
steel into the cutting area greatly simplifies the cutting
of some metals. When the oxides of a metal have a
higher melting point than the metal itself, the oxides
protect the base metal from the cutting action of the
oxygen. In such a metal, introducing iron or low-carbon steel into the cutting area solves the problem because the rapid oxidation of the iron or steel liberates
enough heat to melt the oxides that would otherwise
interfere with the cutting. When alloying elements are
responsible for the difficulty of cutting the metal, the
introduction of iron or low-carbon steel reduces the
percentage of these alloying elements and so makes
the metal easier to cut.
PREHEAT.—Preheating the metal before cutting
reduces the amount of oxygen and fuel gas required to
make the cut. It also tends to prevent or minimize
distortion and to prevent surface hardness of the piece
after the cut has been made. While preheating is
helpful in any cutting operation, it is essential for some
of the metals and alloys that are not easily cut. The
preheating temperatures generally used for
oxyacetylene cutting range from 200° to about 600°F,
although considerably higher temperatures are
occasionally used.
Several techniques are used to introduce iron or
low-carbon steel into the cutting area. An easily cut
steel waster plate may be clamped firmly to the surface
of the metal to be cut; a steel welding rod may be fed
into the kerf as the cutting proceeds; a bead of
low-carbon steel may be deposited along the line of cut
before the cut is made; or finely divided iron powder
may be blown into the stream of cutting oxygen
through special orifices in the cutting tip.
Preheating is usually accomplished by using the
preheating orifices in the cutting tip. Special tips
having larger and more numerous preheating orifices
are available for cutting cast iron and other materials
that require intense and widely distributed preheat.
Preheating furnaces are sometimes used to bring heavy
sections to a uniform preheat temperature.
FLAME ADJUSTMENT.—A neutral preheating flame is used for most oxyacetylene cutting. For
some metals, however, other flame adjustments give
better results. For example, a highly carburizing flame
is used for preheating cast iron. The excess acetylene
Cast iron, chromium irons, stainless steels, and
various alloys having small ferrous content can be
successfully cut with the oxyacetylene torch when iron
or low-carbon steel is introduced into the cutting area.
sections of cast iron. View D shows the reciprocating
(or back and forth) torch movement that is most effective for cutting stainless steels.
TORCH MOVEMENTS.—For most oxyacetylene cutting, the torch is moved steadily forward along
the line of cut, as shown in view A of figure 8-23.
Metals that are difficult to cut often require special
torch movements. For example, the oscillating movement, shown in view B of figure 8-23, is suitable for
cutting thin sections of cast iron; view C shows the
oscillating movement that is best for cutting heavier
FLUXES.—Although fluxes are not used for most
oxyacetylene cutting, they are used for cutting
stainless steels, chromium irons, and other metals that
are hard to cut. Fluxes used for cutting are nonmetallic
compounds in powder form. As the powdered flux is
injected into the kerf, it reacts chemically with the
oxides, which have a higher melting point than the base
metal. The result of this chemical reaction is a slag that
melts at a lower temperature. The stream of cutting
oxygen washes the molten slag out of the cut and
exposes the base metal to the cutting action of the
Fluxes are introduced into the cut by means of an
attachment to the standard cutting torch. The
attachment, shown in figure 8-24, consists of a canister
for holding the flux, a length of air hose, and a copper
tube that is secured to the cutting torch with clamps.
Air pressure forces the powdered flux into the kerf; the
stream of cutting oxygen carries the flux deeper into
the kerf.
Judging the Quality of Oxyacetylene Cuts
To know how good a job of cutting you are doing,
you must know what constitutes a good oxyacetylene
torch cut. In general, the quality of an oxyacetylene cut
is judged by (1) the shape and length of the drag lines,
(2) the smoothness of the sides, (3) the sharpness of
Figure 8-23.—Manipulation of the oxyacetylene cutting torch.
Figure 8-24.—Flux cutting attachment.
are short and almost vertical, the smoothness of the
sides, the sharpness of the top edges, and the slag
conditions are almost sure to be satisfactory.
the top edges, and (4) the amount of slag adhering to
the metal.
DRAG LINES.—Drag lines are the line markings
that show on the cut surfaces. Good drag lines are
almost straight up and down, as shown in view A of
figure 8-25. Poor drag lines are long and irregular or
excessively curved, as shown in view B of figure 8-25;
drag lines of this type indicate poor cutting procedure
which may also result in loss of the cut (views B and
C of fig. 8-25).
oxyacetylene cut shows smooth sides. A grooved,
fluted, or ragged cut surface indicates a cut of poor
resulting from an oxyacetylene cut should be sharp and
square (view D, fig. 8-25). Rounded top edges, such
as those shown in view E of figure 8-25, are not
considered satisfactory. Melting down of the top edges
may result from incorrect preheating procedures or
from moving the torch too slowly.
Drag lines are probably the best single indication
of the quality of an oxyacetylene cut. If the drag lines
SLAG CONDITIONS.—An oxyacetylene cut is
not considered satisfactory if slag adheres so tightly to
the metal that it is difficult to remove.
In all cutting operations, be careful to see that hot
slag does not come in contact with any combustible
material. Globules of hot slag can roll along a deck for
quite a distance. Do not cut within 30 or 40 feet of
unprotected combustible materials. If combustible
materials cannot be removed, cover them with sheet
metal or noncombustible materials. Keep the acetylene
and oxygen cylinders far enough away from the work
so that hot slag will not fall on the cylinders.
Many of the safety precautions discussed in
chapter 1 of this training manual apply to cutting as
well as to welding. Be sure that you are entirely
familiar with all appropriate safety precautions before
attempting any oxyacetylene cutting operation.
Oxyacetylene welding may be accomplished by
either the forehand or the backhand method. Each of
these techniques has special advantages; you should
be skillful with both. Whether a technique is
considered to be forehand or backhand depends on the
relative position of the torch tip and filler rod in
relationship to the direction of welding. The best
technique to use depends upon the type of joint, its
position, and the necessity for controlling the heat on
the parts to be welded.
FOREHAND WELDING (also called puddle welding or ripple welding) is the oldest method of welding.
Figure 8-25.—Effects of correct and incorrect cutting
The filler rod is kept ahead of the torch tip in the
direction in which the weld is being made. Point the
flame in the direction of the welding and hold the torch
tip at an angle of about 45° to 60° to the plates. (See fig.
8-26.) This position of the flame preheats the edges you
are welding just ahead of the molten puddle. By moving
the torch tip and filler rod back and forth in opposite,
semicircular paths, you balance the heat to melt the end
of the filler rod and the side walls of the joint into a
uniformly distributed molten puddle. As the flame
passes the filler rod, it melts off a short length of the
filler rod and adds it to the puddle. The motion of the
torch tip distributes the molten metal evenly to both
edges of the joint and to the molten puddle. This method
is used in all positions for welding sheets and light plates
up to one-eighth inch thick because it permits better
control of a small puddle and results in a smoother weld.
The forehand technique is not the best method for welding heavy plate.
BACKHAND WELDING is a newer method of
welding. In this method, the torch tip precedes the filler
rod in the direction of welding, and the flame is pointed
back at the molten puddle and the completed weld. The
end of the filler rod is placed between the torch tip and
the molten puddle, and the welding torch tip should
make an angle of about 45° to 60° with the plates or joint
being welded. (See fig. 8-27.)
Less motion is required in the backhand method
than in the forehand method. If you use a straight filler
rod, it should be rotated so that the end will roll from
side to side and melt off evenly. You may also bend the
filler rod and, when welding, move the filler rod and
torch tip back and forth at a rather rapid rate. If you are
making a large weld, you should move the filler rod so
as to make complete circles in the molten puddle. The
Figure 8-27.—Backhand welding.
torch tip is moved back and forth across the weld while
it is advanced slowly and uniformly in the direction of
the welding. You’ll find the backhand method best for
welding material more than one-eighth inch thick. You
can use a narrower V at the joint than is possible in
forehand welding. An included angle of 60° is a sufficient angle of bevel to get a good joint. It doesn’t take
as much filler rod or puddling for the backhand method
as it does for the forehand method.
By using the backhand technique on heavier material, you can obtain increased welding speeds, better
control of the larger puddle, and more complete fusion
at the root of the weld. Further, by using a reducing
flame with the backhand technique, a smaller amount of
base metal is melted while welding the joint. When
welding steel with a backhand technique and a reducing
flame, the absorption of carbon by a thin surface layer
of metal reduces the melting point of the steel. This
speeds up the welding operation.
MULTILAYER WELDING is used in welding
thick plate and pipe to avoid carrying too large a
puddle of molten metal, which is difficult to control.
Concentrate on getting a good weld at the bottom of
the V in the first pass. Then in the next layers,
concentrate on getting good fusion with the sides of
the V and the previous layer. The final layer is easily
controlled to get a smooth surface. This method of
welding has an added advantage in that it refines one
layer as the succeeding layer is made. In effect, it heat
treats the weld metal by allowing one layer to cool to
a black heat before it is reheated. This improves the
ductility of the weld metal. If this added quality is
desired in the last layer, an additional or succeeding
layer is deposited and then machined off.
Figure 8-26.—Forehand welding.
A good weld bead must be of uniform width at the
weld face and must have a weld surface that is slightly
below the surface of the base metal. The surface of the
weld should be covered with a thin film of oxides. The
speed with which the flame is carried along the plate
should be regulated to obtain good fusion without
burning through the metal.
A great deal of practice is required to master the
techniques of welding. A good way to acquire skill in
oxyacetylene welding is to practice on scrap pieces of
mild steel (sheet of plate). Try your hand at the various
problems described in the following section.
Oxyacetylene welding may be done in any position. In
the examples given here, we will start with the flat
position, since this is usually the easiest, and go on to
the more difficult positions. Before trying any of these
projects, be sure that the equipment is set up properly
and that all safety precautions are being observed.
Until you have gained considerable skill in welding,
your practice should be done under the supervision of
an experienced welder.
When you have developed skill in running a bead
without filler on a piece of one-eighth inch mild steel,
try the same thing on a piece of thinner stock. A bead
without filler can be used to join two pieces along an
edge, in the manner shown in figure 8-29. To do this,
tack weld the ends by fusing them together; then start
a puddle and run a bead along the edges.
Running a Bead With Filler (Flat Position)
Running a Bead Without Filler (Flat Position)
The next step in learning to perform oxyacetylene
welding is to run a bead in the flat position, using filler
metal. This job is very similar to the first one, but
requires manipulation of a filler rod as well as of the
torch tip. The bead is built up by the filler metal, as
shown in figure 8-30; it should be built up about 25
For this project, you are not welding two pieces
together but are merely running a bead. Select a piece
of plate about 2 inches by 4 inches by 1/8 inch thick.
Place the two firebricks as shown in figure 8-28.
If you are right handed, start at the right and work
to the left. If you are left handed, start at the left and
work to the right. Hold the torch so that the tip forms
a 45-degree angle with the plate along the line of weld.
Direct the inner cone of the flame at a point near the
right edge of the metal and hold it there until a molten
puddle forms. Keep the tip of the cone from
one-sixteenth to one-eighth inch away from the surface
of the molten metal. As soon as the puddle is formed,
move the torch tip slowly forward with a slight
weaving or oscillating motion, as indicated in figure
8-28. Both the forward motion and the weaving motion
must be uniform to produce a smooth, regular bead.
Figure 8-29.—Bead weld without filler, used to join two pieces
along an edge.
Figure 8-28.—Running a bead without using filler rod (flat
Figure 8-30.—Bead weld with filler (flat position).
percent, or an amount equal to one-fourth the thickness
of the stock.
Start the puddle in the usual way. As soon as the
puddle is formed, dip the filler rod into the middle of
the puddle. Oscillate both the filler rod and the torch
tip. The filler rod should be moved in a direction
OPPOSITE to the direction of movement of the flame.
When the flame is on one side of the puddle, the rod
should be on the other side. Stir the end of the rod in
the puddle, not above it. Do not direct the flame at the
end of the filler rod; the filler rod should be melted by
the puddle, not by the flame. Direct the flame so that
it preheats the weld area uniformly. The direction of
the flame is very important from the point of view of
obtaining good fusion and avoiding undercutting or
Figure 8-31.—Welding a butt joint in the flat position.
distribute it evenly along the joint. Bending the filler
rod to an angle of 90°, a short distance from the end,
makes it easier to get the end of the filler rod into the
puddle. Figure 8-32 shows the positions of the torch
tip and the filler rod with respect to the base metal.
Making a Butt Joint (Flat Position)
Butt welding in the flat position is often used to
join sheet metal. First tack the two pieces of sheet
together, leaving a slight gap for a root opening. Be
sure the flame is correctly adjusted to a neutral or
slightly carburizing flame. Let the tacks cool, and then
start a puddle at one end.
Making a Butt Joint (Overhead Position)
When welding in the overhead position, you will
have to overcome the tendency of the molten metal to
drop down or to sag on the plate. Keeping the puddle
small helps to control the molten metal. If the molten
puddle gets too large, remove the flame for an instant
to allow the metal to freeze; then resume the welding.
The position of the torch tip and the filler rod must
be just right to achieve the fusion and penetration
required for a good weld of this type. Hold the torch
tip at an angle of 45° to the base metal, as shown in
figure 8-31. Apply the flame at the root of the joint,
first to one part of the joint and then to the other until
the side walls melt or break down to form a pool of
molten metal that bridges the gap between the plates
at the root. Add filler metal to the molten pool until the
pool is sufficiently large. Carry the puddle forward by
manipulating the torch with an oscillating motion. If
you weave the torch tip and the filler rod correctly, you
can carry along a molten puddle that will give
complete penetration and also provide enough filler
metal to reinforce the weld. Avoid overheating the
puddle; overheating can actually bum the metal and
thus greatly impair the strength of the finished weld.
Figure 8-33 illustrates the welding of a butt joint
in the overhead position. Direct the flame so that it will
melt both edges. Add enough filler to keep the puddle
the right size and to provide some metal for
Making a Butt Joint (Vertical Position)
When welding in the vertical position, you have
the problem of keeping the molten metal from running
down and accumulating at the bottom of the joint. To
control the flow of molten metal, hold the flame below
the filler rod. The flame should point upward at an
angle of 45° to the base metal. The gas pressure from
the torch tip will support the molten metal and
Figure 8-32.—Welding a butt joint in the vertical position.
Figure 8-35.—Edge joints for sheet and plate.
Figure 8-33.—Welding a butt joint in the overhead position.
heavier sections, V-bevel or U-groove the lapped plate
to permit penetration to the root of the joint.
reinforcement of the weld. Keep the flame in such a
position that it will support the molten metal and
distribute it along the joint. Use a small filler rod; this
will help you to keep the puddle small. In many
overhead welding jobs, it is possible to weld from one
side only. In such cases, particular care is required to
make sure the heat is evenly distributed, so that one
plate will not be burned through.
View B of figure 8-34 shows an OPEN corner joint
that is often used on heavy sheets and plates. To make
this joint, melt down the edges of the plate and add
enough filler metal to build up the comer from one
View C shows an open corner joint that is welded
from both sides. First weld the joint from the outside,
then reinforce the joint and seal it (as for use in drip
pans) from the inside with a seal bead weld.
Making a Corner Joint
The comer joint is used to join the edges of two
plates when the surfaces of the plates make a 90-degree
angle with each other. Figure 8-34 shows three designs
that are commonly used for corner joints. The
CLOSED comer joint (view A) is used on lighter
sheets and plates where strength requirements for the
joint are not a factor. In making this joint, melt the
overlapping edge with the torch and add only a small
amount of filler metal. When using this joint design for
Making an Edge Joint
Edge joints are used mainly to join the edges of
sheet metal and to weld reinforcing plates on flanges
of I-beams or edges of angles. Figure 8-35 shows two
common types of edge joints. The joint shown in view
A is used for welding thin sheets; this joint requires no
edge preparation other than cleaning the edges and
tacking them together. The joint shown in view B is
used for heavier plate. To make this joint, bevel the
edges to allow good penetration and fusion of the side
walls. In making both of these joints, use enough filler
metal to fuse both edges and to reinforce the joint.
Making a Lap Joint
The lap joint is the simplest of all weld joints and
is formed by overlapping two plates of metal. Lap
joints may be welded from one side or from two sides.
They are stronger when welded from both sides, but
even a lap joint that is welded from only one side is
stronger than a butt joint in some applications.
Figure 8-34.—Corner joints. A. Closed joint. B. Open joint,
welded from one side. C. Open joint, welded from both
the selection of the proper welding rod. Low-alloy
steels usually require preheating and postheating.
Making a Joint
The T joint is another simple joint that is formed
by butting the edge of a piece of plate up to the face of
another plate to form the letter T. A plain T joint in thin
material requires little preparation. For thicker plate,
the edges should be prepared as shown in figure 8-36.
As the carbon content increases, steels become
more difficult to weld. Steels with a carbon content of
0.30 to 0.50 percent should be welded with a slightly
reducing (carburizing) flame, and should be
postheated to develop the best physical properties and
to reduce internal stress.
High-carbon steels and tool steels require
somewhat special techniques if they are to be
successfully welded. Slow preheating to about 1000°F
is required; the metal should be protected from drafts
during the preheating. No flux is required. The welding
should be completed as rapidly as possible with a
carburizing flame. The filler rod and the torch tip
should not be manipulated for the welding of
high-carbon steels and tool steels. Filler metal should
be added in small amounts, just as it is needed. A
smaller flame and a lower gas pressure should be used
for these materials than for low-carbon steel since
there is even more danger of overheating the
high-carbon steels and the tool steels. High-carbon
steels and tool steels must be heat treated after
Low-carbon steel, low-alloy steel, cast steel, and
wrought iron are easily welded by the oxyacetylene
process. A flux is not necessary with these materials,
since the oxides melt at a lower temperature than the
base metal. You must keep the molten puddle of metal
enclosed by an envelope of flame at all times during
the welding process. If the metal is permitted to come
in contact with the air while it is in a molten condition,
it will oxidize rapidly. Care should be taken to prevent
overheating the metal. Use a neutral or slightly
reducing (carburizing) flame. Do NOT use an
oxidizing flame. Manipulate the torch and the filler rod
so that the top of the oxyacetylene cone is about
one-sixteenth to one-eighth inch from the surface of
the metal. Melt the end of the filler rod in the puddle,
not with the flame. The welding of low-carbon steels
and cast steels presents no special problems other than
The procedure for oxyacetylene welding of
wrought iron is the same as for low-carbon steel.
However, certain special considerations should be
Figure 8-36.—Edge preparation required for various types of T joints.
kept in mind. Wrought iron contains a slag that is
incorporated in it during the manufacturing process.
This slag gives the surface of the molten puddle of
weld metal a greasy appearance. Do not confuse this
greasy appearance with the appearance of actual
fusion. Continue heating the metal until the side walls
of the joint break down into the puddle. Best results
with wrought iron are obtained when the filler metal
(usually mild steel) and the base metal are mixed in the
molten puddle with as little agitation as possible.
Although brazing is used extensively to make
joints in nonferrous metals, there are many situations
in which oxyacetylene welding is suitable for this
purpose. In general, joint designs are the same for
nonferrous metals as for ferrous metals. Oxyacetylene
welding of nonferrous metals may require mechanical
cleaning of the surfaces before welding and the use of
a flux during welding. Filler metal must be suitable for
the base metal being welded.
Oxyacetylene welding of cast iron requires
different procedures than those used for welding
steels. Special edge preparation is usually required.
The entire weldment should be preheated to between
750° and 900°F before the welding is begun. The
welding should be done with a neutral flame, by a
backhand technique. Use a cast iron filler metal. Flux
is required but should be used sparingly, as needed, to
overcome temporary difficulties. The filler metal is
added by directing the inner cone of the flame against
the rod into the puddle. The filler metal should be
deposited in layers that are no more than one-eighth
inch thick. The weldment must be stress relieved after
welding; heat it to a temperature of between 1100° and
1150°F and then cool it slowly.
Where high joint strength is required, the only kind
of copper that can be successfully welded by
oxyacetylene welding is DEOXIDIZED copper
(copper that contains no oxygen). Either a neutral or a
slightly oxidizing flame adjustment may be used. With
a neutral flame, a flux is necessary; with an oxidizing
flame, no flux is needed because the oxide formed on
the surface protects the molten metal. Because of the
high thermal conductivity of copper, it is necessary to
preheat the joint area to between 500° and 800°F and
to use a large size torch tip for welding. The larger size
tip supplies more heat to the joint and thus makes it
possible to maintain the required temperature at the
joint. After welding has been completed, the part
should be cooled slowly.
Oxyacetylene welding is successful with some
chromium-nickel steels (stainless steels). As a rule,
oxyacetylene welding is used only for light gauge
sheet metal. Heavier pieces of these steels are usually
joined by one of the electric arc welding processes,
which will be discussed in chapter 10. On material
0.040 inch or less in thickness, a flange equal to the
thickness of the metal is turned up and the weld is made
without filler metal. Before being welded, the joint
surfaces of the metal should be cleaned with sandpaper
or other abrasive and then coated with stainless steel
flux. The torch tip used for welding stainless steel
should be one or two sizes smaller than the tip used to
weld mild steel of the same thickness. The torch should
be adjusted to produce a carburizing flame that has an
excess acetylene feather extending about
one-sixteenth inch beyond the tip of the inner cone, as
seen through the goggles. The torch should be held so
that the flame makes an angle of 80° with the surface
of the sheet. The tip of the cone should almost, but not
quite, touch the molten metal. Make the weld in one
pass, using a forehand technique. Do not puddle or
retrace the weld. Uniform speed is essential in welding
stainless steels. If it is necessary to stop the welding
before it is completed, or to reweld a section, wait until
the entire weld has cooled before beginning to weld
Copper-Zinc Alloys
Copper-zinc alloys (brasses) may be welded in the
same way as deoxidized copper. However, a
silicon-copper rod is used for welding brasses. Preheat
temperature is from 200° to 300°F. Copper-silicon
alloy (silicon bronze) requires a different oxyacetylene
welding technique. This material should be welded
with a slightly oxidizing flame. A flux with a high
boric acid content should be used. Add filler metal of
the same composition as the base metal; as the weld
progresses, dip the tip of the rod under the viscous film
that covers the puddle. Keep the puddle small so that
the weld will solidify rapidly.
Copper-Nickel Alloys
Oxyacetylene welding of copper-nickel alloys
requires surface preparation and preheating. The flux
used for this welding is in the form of a thin paste; it
is applied by brush to all parts of the joint and to the
welding rod. The torch should be adjusted to give a
For oxyacetylene welding of lead, the filler metal
should be of the same composition as the base metal.
The molten puddle is controlled and distributed by
manipulating the torch so that the flame moves in a
semicircular or V-shaped pattern. Each tiny segment
of the weld is made separately, and the torch is flicked
away at the completion of each semicircular or
V-shaped movement. Joints are made in thin layers.
Filler metal is not added on the first pass, but is added
on subsequent passes. When welding lead or lead
alloys, wear a respirator of a type approved for
protection against lead fumes. LEAD FUMES ARE
slightly carburizing flame; the tip of the inner cone
should just touch the base metal. Do not melt the base
metal any more than is required to give good fusion.
Keep the end of the welding rod within the protective
envelope of the flame, adding the filler metal without
agitating the molten puddle. Run the weld from one
end of the joint to the other without stopping. After
welding is completed, cool the part slowly and then
remove the remaining traces of flux with warm water.
Nickel and High-Nickel Alloys
Oxyacetylene welding of nickel and high-nickel
alloys is similar to that for copper-nickel alloys. Good
mechanical cleaning of the joint surfaces is essential.
Plain nickel is welded without a flux, but high-nickel
alloys require a special boron-free and borax-free flux
in the form of a thin paste. The flux is applied by brush
to both sides of the seam, to the top and bottom, and to
the welding rod. The torch should be adjusted to give
a slightly carburizing flame; the tip selected should be
the same size as (or one size larger than) for steel of
the same thickness. Keep the tip of the cone in contact
with the molten puddle, and keep the welding rod well
within the protective envelope of the flame at all times.
After the weld is completed, postheat the part and cool
it slowly. Then remove the flux with warm water.
Whether you are welding, torch brazing, flame
cutting, or heating with oxyacetylene equipment,
certain precautions must be observed to protect
personnel and the structure from injury by fire or
explosion. The precautions that follow apply
specifically to oxyacetylene work. Other safety
precautions are listed in chapter 1 of this manual and
in OPNAVINST 5 100.19.
1. CLOTHING: You should use goggles, a
faceplate, respirators, flameproof gloves, jackets,
leggings, and boots, as appropriate. Do not keep any
type of lighter on your person and do not wear synthetic
Oxyacetylene welding of lead requires special
tools and special techniques. A flux is not required.
The metal in the joint area must be thoroughly cleaned
before welding. This cleaning is accomplished by
shaving the joint surfaces with a scraper and then
wire-brushing the metal with a clean stainless steel
wire brush to remove oxides and foreign matter. The
lap joint is used for practically all oxyacetylene
welding of lead, except that a square butt joint may be
used when the welding is done in the flat position.
When the lap joint is used, the edges should overlap
each other from 1/2 inch to 2 inches, depending upon
the thickness of the lead.
2. CYLINDER SAFETY: You should follow these
safety precautions when working with compressed gas
cylinders during cutting or welding operations:
— Place cylinders a safe distance away from the
actual welding or cutting operations so that
sparks, hot slag, or flame will not touch them.
— Do not tamper with, or attempt to repair,
cylinder valves.
— Always place fuel-gas cylinders with the valve
end up. Acetylene cylinders should be stored in
the vertical position for a minimum of 2 hours
before use to stabilize the gas.
A special lightweight torch is used for the
oxyacetylene welding of lead. The gas pressures range
from 1 1/2 to 5 psi. A completely neutral flame must
be used; the length of the flame should be somewhere
between 1 1/2 to 4 inches, depending upon the gas
pressures that are used. A soft, bushy flame is best for
welding lead in the horizontal position and in the flat
position. A more pointed flame gives better results in
the vertical position and in the overhead position.
— Handle cylinders carefully; avoid rough
handling that could damage cylinders.
— Close cylinder valve and release gas from the
regulator before attempting to remove the
regulator from the cylinder valve.
— Do not place anything on top of an acetylene
cylinder that may interfere with the quick
closing of the cylinder valve.
— When lighting the torch, open the acetylene
valve first and ignite the gas before introducing
oxygen to the flame.
— Always use regulators to reduce compressed
gases to a suitable working pressure.
— Never allow unburned acetylene to escape into
small or closed spaces.
— Copper tubing should not be used with acetylene
gas because of the potential of an explosive
chemical reaction.
— Report any safety discrepancy or unsafe act to
your immediate supervisor.
system is thoroughly purged of air and all connections
in the system are tight before the torch is ignited, the
flame is likely to bum inside the torch instead of outside
the tip. The difference between the two terms backfire
and flashback is this: in a backfire, there is a momentary
burning back of the flame into the torch tip; in a
flashback, the flame bums in or beyond the torch mixing
chamber. A backfire is characterized by a loud snap or
pop as the flame goes out. A flashback is usually
accompanied by a hissing or squealing sound. At the
same time, the flame at the tip becomes smoky and sharp
pointed. When a flashback occurs, immediately shut off
the torch oxygen valve, then close the acetylene valve.
By closing the oxygen valve, the flashback is stopped at
once. The occurrence of a flashback indicates that
something is radically wrong either with the torch or
with the manner of handling it. A backfire is less serious.
Usually the flame can be relighted without difficulty. If
backfiring continues whenever the torch is relighted,
check for these causes: overheated tip, gas working
pressures greater than that recommended for the tip size
being used, loose tip, or dirt on the torch tip seat. These
same difficulties may be the cause of a flashback, except
that the difficulty is present to a greater degree. For
example, the torch head may be distorted or cracked.
3. OPERATIONS: The improper operation of
oxyacetylene equipment is the major cause of accidents.
Follow these basic safety precautions when operating
oxyacetylene equipment:
— Check all gas connections for leakage.
— Do not use defective or damaged equipment.
— Never use petroleum-based products (oil or
grease) to lubricate oxyacetylene equipment.
Oil or grease in the presence of oxygen under
pressure will ignite violently.
NOTE: Glycerin is a suitable lubricant for
oxyacetylene equipment.
— Do not use vice grips, adjustable wrenches,
pliers, or other similar tools to tighten
connections or to open gas cylinder valves. You
will only damage the connections rendering
them unusable in an emergency.
— Always leave the apparatus wrench on the
acetylene cylinder valve so the cylinder can be
secured quickly in an emergency.
— Never open an acetylene cylinder valve more
than 1/4 to 1/2 of a turn.
In most instances, backfires and flashbacks result
from carelessness. These difficulties can be avoided
by making certain that (1) all connections in the system
are clean and tight; (2) torch valves are closed (not
open or merely loosely closed) when the equipment is
stowed; (3) the oxygen and acetylene working
pressures used are those recommended for the torch
employed; and (4) the system is purged of air before
the apparatus is used. Purging the system of air is
especially necessary when the hose and torch have
been newly connected or a new cylinder is
incorporated into the system. Purging a system is
accomplished as follows: Close torch valves tightly,
then slowly open the cylinder valves. Next, open the
regulator slightly. Open the torch acetylene valve and
allow acetylene to escape for 5 to 15 seconds,
depending on the length of the hose. Close the
— Fully back out the adjusting screw on a regulator
and stand to one side when pressurizing a
compressed gas system. Regulators have been
known to explode if pressurized improperly.
— Never run oxyacetylene hoses on the deck. The
hoses should always be run in the overhead.
When running hoses through hatches, doors, or
scuttles, locate the connection near the access
and block open the door to prevent the hose from
being cut.
— Never use matches, lighters, or any open flame
to light your torch; use a friction lighter only.
Butane lighters have been known to explode if
exposed to excessive heat or if the casing melts.
oxyacetylene equipment and the use of the equipment.
You also have the information required to perform
certain welding techniques and oxyacetylene cutting
operations. Review of the safety precautions is highly
recommended. Failure to obey some of the
precautions could cause a fire, personnel injury, or
equipment damage. However, failure to follow other
precautions may just cost you your life.
acetylene valve. Repeat the procedure on the oxygen
side of the system. After purging air from the system,
light the torch as described previously.
As you look back at this chapterr, you will find
that you now have a knowledge of the components of
Upon completion of this chapter; you should be able to do the following:
Identify the tools and equipment used in silver brazing.
Describe the techniques used in braze welding and silver brazing, and define the
different types of filler metals available.
Explain the necessity of using fluxes, the different types of flux available, and the
correct procedures to use in applying fluxes.
Describe the procedures for hydrostatically testing silver-brazed joints.
Describe hard surfacing and identify the materials and techniques used in hard
Describe the uses of powdered metals and the correct procedures in the application
of powdered metals.
Describe the technique used in soldering.
You will often see the word tinning used in
connection with silver brazing and braze welding. The
surface of the base metal is said to be tinned when a very
thin continuous film of tiller metal precedes the main
part of the filler metal. Tinning can only occur on metal
that has been cleaned, fluxed, and heated to the correct
temperature. If tinning does not occur, the main part of
the filler metal will not adhere to the base metal. Tinning
will be discussed later in this chapter.
This chapter will cover silver brazing, braze
welding, surfacing, powdered metal flame spraying,
and soldering processes. The various associated
equipment will also be discussed along with its safe
operation. You will find that silver brazing and braze
welding are two welding processes that you will use
quite often. There are a number of ways to silver braze,
but it is done most often with an oxyacetylene torch.
Braze welding and silver brazing are similar in
many ways, but they are two different welding
processes. In silver brazing, a silver-base alloy is used
as a filler metal and the base metal is NEVER melted.
The filler metal is distributed throughout the joint by
capillary attraction. In braze welding, a copper-base
alloy is used as a filler metal and it is deposited in groove
and fillet welds exactly at the points where it is to be
used. Limited base metal fusion may also occur in braze
welding; capillary attraction is not a factor.
Silver brazing is a process where coalescence is
produced by heating with a gas flame. It uses a silver
alloy filler metal with a melting point above 800°F, but
below the melting point of the base metal. The filler
metal is distributed in the joint by capillary attraction.
Let’s consider some everyday examples of the
process used in silver brazing. When you use a blotter,
the ink is drawn up into the blotter by capillary
attraction. The wick on an oil lamp can be lit because
the oil rises in the wick by capillary attraction. In each
of these examples, we have a liquid that moves into an
opening in a solid by the process called capillary
attraction. A basic rule of the process is that the distance
the liquid will be drawn into the opening in the solid
depends on the size of the opening in the solid. The
smaller the opening, the farther the liquid will be drawn
This same capillary attraction causes the melted
filler metal used in silver brazing to be drawn into the
narrow clearance between the joining members.
Capillary attraction will not work unless the tiller metal
is in a fluid state and the size of the opening is quite
small (usually 0 to 0.012 depending on pipe or tube
size). Therefore, the application of heat and the use of
a very small clearance between joining members are
essential to silver brazing. The heat is necessary to melt
the filler metal and to keep it molten. The small
clearance is necessary to allow capillary attraction to
draw the molten metal into the space between the joint
Figure 9-1.—Lightweight oxyacetylene torches with flexible
extension tubes.
You will often hear silver brazing called SILVER
is similar in many respects to soldering. The basic
distinction between a welding process and a soldering
process is that the metals or alloys used for a welding
process have melting points above 800°F, while those
used for a true (or SOFT) soldering process have
melting points below 800°F.
Figure 9-2.—Tip designs.
Silver brazing depends largely upon the operator’s
manipulation of the torch to control the application of
heat. A lightweight torch with or without a flexible
extension tube (fig. 9-1) simplifies the silver brazing
procedure and helps reduce operator fatigue. The
flexible extension tube is made of soft copper. It can be
bent as needed to heat the surfaces to be joined.
The size of tip selected for the torch should be
determined by the size and type of work to be done. For
silver brazing sheet stock, for instance, you would
ordinarily use size 4, 5, or 6. Table 9-1 may be used as
a general guide.
Since one tip size cannot be used for making joints
on all thicknesses of metal, torches are provided with
various sizes of tips. Tips are designed to heat a large
area and still allow little or no “bounce” (reflected heat).
Figure 9-2 shows the shapes of the flame at the ends of
different kinds of tips.
Silver brazing filler metals are nonferrous metals or
alloys that have a melting temperature above 800°F, but
below the melting point of the base metal being joined.
You may have heard these silver brazing filler metals
referred to as silver solder, hard solder, or brazing
alloys, but the correct term is silver brazing filler metals.
The tip shown in view A of figure 9-2 has the lowest
velocity and heats the largest area. This tip should be
used in joining with silver alloys.
Table 9-1.—Tip Sizes and Gas Pressures for Silver Brazing Various Thicknesses of Metal
Tip No. (Bulboustype tips)
Metal thickness
Oxygen pressure
Acetylene pressure
3/4 & over
Silver brazing filler metals covered in Navy
specifications have the following major characteristics:
Grade V is used when the characteristics of grade
IV are required, but where close tolerances cannot be
maintained or when the addition of a filler is desired.
Grade V should be used for brazing hard materials.
Low melting point
High tensile strength
High resistance to corrosion
All silver brazing operations require the use of a
flux. The flux prevents the oxidation of the metal
surfaces and removes oxides already present. Flux also
increases the flow of the brazing filler metal and
increases its ability to adhere to the base metal. It brings
the brazing filler metal into immediate contact with the
metals being joined and permits the tiller to penetrate
the pores of the metal. Silver brazing flux (as specified
in table 9-3) must be applied evenly to each brazing
Flows readily at the lower brazing temperatures
Brazes readily to copper and to copper alloys
The metals commonly used for silver brazing filler
metals include silver, copper, zinc, phosphorus,
cadmium, and nickel. The percentage of the various
metals determines the color, strength, melting point, and
flow point of the filler metal. All grades of silver brazing
alloy can be obtained in strips, wires, pigs, shot, or
chips, as required.
For best results, a flux must become active at a
temperature slightly below the melting point of the filler
metal, and must remain fluid at the brazing temperature.
Regardless of the type of flux you select, you need to
apply it in such a manner that all oxide film is removed.
Table 9-2 lists the silver brazing filler metals
commonly used in the Navy. There are six different
filler metals: grades 0, I, II, III, IV, and V.
Grades 0, I, and II are suitable for joining ferrous
metals. They cost less and are often used for large
quantities of work.
You can get flux in three forms: liquid, paste, and
powder. When used either in paste form or in liquid
form, the flux is applied with a brush to both parts of
the joint and to the filler metal. Use a circular motion to
brush it on, and let the flux extend outside the joint or
fitting. For best results, flux should be applied after
cleaning and before heating. Brush the flux on with a
circular motion to give a uniform coating and lessen the
Grade III is used for brazing copper and
copper-base alloys. It is not intended for use with
ferrous metals.
Grade IV is used for joining ferrous and nonferrous
metals, except those having melting points lower than
the filler metal.
Table 9-2.—Silver Brazing Metals Commonly Used in the Navy
Brazing Filler
Copper-silver 0
Composition (%)
Melting and
Flow Point1
Silver . . . . . . 20
Copper . . . . . 45
Suggested Use
Seal joints operating up to
1230°F. Suitable for
joining ferrous metals.
Strip or
Seal joints operating up to
1050°F. Suitable for
joining ferrous metals.
High silver content
primarily for color match.
Suitable for joining ferrous
Strip or
For brazing copper and
copper-base alloys.
Strip or
For brazing all ferrous and
nonferrous metals except
those having lower melting
points. Use only where
proper tolerances can be
Strip or
For same applications as
grade IV but where close
tolerances cannot be
maintained. For brazing
hard metals.
Zinc . . . . . . . 35
Copper-silver I
Silver . . . . . . 45
Copper . . . . . 30
Zinc . . . . . . . 25
Copper-silver II
Silver . . . . . . 65
Copper . . . . . 20
Zinc . . . . . . . 15
Silver . . . . . . 15
Copper . . . . . 80
Phosphorous . . 5
Copper-silver IV
Silver . . . . . . 50
Copper . . . . . 15
Zinc . . . . . . . 17
Cadmium . . . . 18
Copper-silver V
Silver . . . . . . 50
Copper . . . . . 15
Zinc . . . . . . . 15
Cadmium . . . . 17
Nickel . . . . . . 3
In all instances, the lesser temperature indicates melting point and the higher temperature indicates flow point of the
brazing filler metal.
borax contains approximately 47 percent water of
crystallization (water that is chemically combined in a
crystallized substance). When the borax is heated, this
water is driven off, and the borax appears to boil. Borax
may be mixed with water to form a paste. However,
borax can hold water, and it will quickly take up the
water and become crystalline borax again. If
possibility of bare spots that will oxidize during heating.
Flux the filler metal by heating the filler rod and dipping
it into the flux. Enough flux to do the job will stick to
the hot rod.
Borax or a mixture of borax and other chemicals is
most often used as a flux. Up to a certain point, heat
causes borax to swell and bubble. Common crystalline
Table 9-4.—Maximum Permissible Diametrical Clearances
Table 9-3.—Types of Silver Brazing Fluxes
Brass, copper, tin . . .
Lead . . . . . . . . . .
Iron, steel . . . . . . .
Galvanized iron . . . .
Zinc . . . . . . . . . .
Aluminum . . . . . . .
Tallow, rosin
Borax sal ammoniac
Zinc chloride
Zinc chloride
Stearine, special flux
Pipe or Tube
Size (Inches)
commercial powdered borax is used, see that it is kept
in sealed glass jars.
Maximum Clearances (Inches)
at Ambient Temperature
Class P-3a
Class P-3b
1/4 to 1/2
Over 1/2 to 1
Over 1
If a prepared flux is not available, a mixture of 12
parts of borax and 1 part boric acid may be used as a
flux for brazing.
In fitting up joints for brazing, it is the responsibility of the fabricator to use a clearance within the
limits established by this table, which assures
conformity to inspection or test requirements set
forth in this document or in other specifications or
standards governing brazed piping systems.
When you apply flux or assemble the parts, avoid
handling the polished parts of the joint or you will defeat
the purpose of cleaning. If the parts are not assembled
immediately, the fluxed surfaces should be protected so
that the flux will not be contaminated by dirt or washed
or brushed off. If the coating of flux dries before the
parts are assembled, remove the old flux and apply a
fresh coat of flux. It should always be applied as soon
as a joint area is cleaned, even though it will not be
brazed immediately. Joints that have been assembled
but not brazed within 24 hours must be disassembled,
recleaned, and refluxed before brazing. After you finish
the brazing, allow the work to cool below 200°F before
cleaning the joint with warm water to remove the
residue left by the flux.
High-strength butt joints can be made if a joint
clearance between 0.001 and 0.003 inch can be
maintained in the finished braze. The edges of the joint
must be perfectly square so that you have a uniform
clearance between all portions of the joint surfaces. Butt
joints are usually used where you do not want the double
thickness of a lap joint. In these situations, the scarfjoint
is probably better.
A scarf joint provides an increased area of bond
without increasing the thickness of the joint. The area
of bond, however, depends on the angle at which the
edges of the joint are scarfed. Usually, you will want an
area of bond two to three times that of a butt joint in the
same thickness of material. A 30-degree scarf angle
gives a bond area twice that of a 90-degree butt joint,
and a 19 1/2-degree scarf angle gives a bond area three
times that of a butt joint.
The filler metal used in silver brazing must be
distributed by capillary action. Therefore, the joints
must be of a type that requires closeness of fit. In silver
brazing there are three basic joint designs: lap, butt, and
scarf. The joint members in which these designs are
used may be flat, round, tubular, or irregular in cross
You will use modifications of these basic joint
designs. In some instances, you will add the silver
brazing filler metal when the proper temperature has
been attained. In other instances, you will preplace the
filler metal in the joint before heat is applied. This
technique is common in pipe work where special
fittings containing preinserted rings of silver brazing.
filler metal are used. The technique is also used in sheet
metal work involving locked scams. Here, you will
place the silver brazing filler metal in the seam before
The lap joint design is used most frequently in silver
brazing, especially in pipe work. Good practice requires
a length of lap at least three times the thickness of the
metal being joined. The maximum permissible
diametrical clearances used in silver brazing range from
0.001 to 0.012 depending on the pipe or tube size and
the classification of the brazed piping system. (See table
it is locked. The preplaced insert method produces a
strong leaktight joint in both sheet metal and pipe work.
You will need some knowledge of the principles of
heat flow through metals to understand silver brazing
The following points are particularly important:
1. Heat always flows from a hotter area to a colder
2. The process by which heat flows from molecule
to molecule through a metal (fig. 9-3) is called
conduction. Conduction takes place quite rapidly in
most metals, but air is a very poor conductor of heat.
Therefore, if two pieces of metal that are to be joined
by silver brazing are not in contact with each other, each
piece must be heated separately. If the two pieces are in
contact with each other, you can heat both by applying
heat to one of them. The second piece will be heated by
conduction from the first piece. These principles are
shown in figure 9-4.
Figure 9-4.—Flow of heat.
3. In the molten state, filler metal flows from the
colder toward the hotter areas on a heated surface.
Therefore, you might say that the filler metal flows in a
direction OPPOSITE to the direction of flow of the heat.
This principle is shown in figure 9-5.
4. The filler metal and the flux used in silver
brazing cannot occupy the same space at the same time.
Therefore, a clearance must be provided in the setup of
the joint so that the filler metal can flow in and the flux
can flow out. Heat should be applied in the manner
shown in figure 9-6 so that the flux will flow out when
the filler metal reaches the bonding temperature.
Figure 9-5.—Flow of molten filler metal.
5. Heat travels faster through some metals than
through others (fig. 9-7). All metals and alloys have
high conductivity as compared with most other
substances, but there is a good deal of variation in the
speed with which various metals and alloys will conduct
heat. Copper, for example, is a very rapid conductor of
heat. When two pieces of different metals are to be
joined by silver brazing, the difference in heat
conductivity of the two metals causes some problems
in heating. For example, if you are trying to join a steel
part and a copper part by silver brazing, you will find
that the steel part reaches the joining temperature more
rapidly and has a tendency to overheat because the heat
Figure 9-3.—Conduction of heat.
Figure 9-6.—Flow of flux and filler metal.
is carried away from it more slowly. The copper part,
on the other hand, conducts heat away from the brazing
area more rapidly than does the steel part. Therefore,
more heat is required to bring the copper part to the
brazing temperature.
Control of heat is one of the most difficult parts of
silver brazing. To do it properly, you must manipulate
the torch correctly, and you must remember the points
just discussed concerning the flow of heat through
metals. Basically, the problem of heat control in silver
brazing is one of bringing BOTH parts to the correct
temperature at the same time. If one piece is hot enough
but the other is not, the filler metal will flow onto the
hot piece, but it will not bond to the cooler piece.
If you have heavy and thin metal sections that must
be silver brazed, be careful to avoid overheating the thin
part. A good example is the silver brazing of thin copper
tubing to a heavy cast fitting. If the same amount of heat
were applied to the tubing as to the casting, the tubing
would be overheated and probably burned. Therefore,
most of the heat must be directed toward the heavier
part. Frequently, heavy parts and large areas must be
Figure 9-7.—Relative rate of heat flow through copper,
nickel-copper alloy, and steel.
preheated for best brazing results. Preheating may be
done with a forge, a furnace, or a welding torch.
Joints must be clean and properly fitted for
satisfactory silver brazing. All parts to be brazed must
be thoroughly cleaned to remove surface scale, oxide,
Figure 9-8.—Applying heat for silver brazing a tube and fitting.
Rust and corrosion should be removed by sanding,
grinding, sandblasting, wire brushing, or filing. Oil and
grease should be removed with solutions of
trichloroethylene or trisodium phosphate, not by heat.
The cleaned surfaces should not be handled unnecessarily. When parts have been cleaned and the
elapsed time before fluxing is more than 8 hours, the
parts should be recleaned. Brazing alloy should be free
of all visible oxides, grease, oil, or other foreign
substances when assembled or fed into the joint. Never
try to braze dirty metal.
Use a slightly carburizing flame to apply heat with
the oxyacetylene torch for brazing with a silver-base
filler metal. Select a torch tip to suit the type of work
you are doing. Ordinarily a size 4, 5, or 6 tip is suitable
for silver brazing. Keep the inner cone of the flame from
one-fourth to one-half inch away from the metal. Play
oil, and grease. Any one or a combination of the
following methods must be used for the cleaning of
scale and oxides or other foreign substances:
Abrasive cloth, followed by wiping with an
acetone-, alcohol-, or water-damp clean cloth.
Stainless steel wire brush, hand or rotary,
followed by wiping with an acetone-, alcohol-,
or waterdamp clean cloth.
Metallic stainless steel wool followed by wiping
with an acetone-, alcohol-, or water-damp clean
Commercial cleaning solutions or degreasing
baths may be used when included in an approved
brazing procedure or specification.
the flame over the surface with a circular, sweeping
motion so that you obtain uniform heating of the parts
to be joined. The flame should be soft so that it will not
blow or boil the molten filler metal.
Bring up the temperature of the parts until the flux
on them is melted. Continue heating the parts to be
joined until they are hot enough to melt the tiller rod.
The filler should be melted by the heat of the joint, not
by the flame. It should flow like water wherever the flux
has been applied. Avoid overheating. Use just enough
heat to get the parts of the joint hot enough to melt the
filler metal so that it can flow.
Two methods are used to make joints with silverbase brazing filler metal: the insert method and the
feed-in method (more commonly referred to as face
feeding). With either method, the parts must be
adequately supported during heating to maintain
alignment and tolerances or fit. The work must be held
firmly in positionuntil the silver brazing tiller metal has
completely solidified.
When you use the insert method, insert a strip of the
silver-base filler metal in the joint before assembly.
Before brazing the parts, clean them with emery cloth,
sandpaper, or some other abrasive, and apply flux with
a brush. Next, fit the two parts together and align them.
Then, light-off the torch and direct the heat on the tube
or thinner portion, as shown in figure 9-8. The lines
drawn on the tube indicate the path of the torch while
the tube is being heated.
Heat applied to the tubing causes it to swell. This
brings the surface of the tube into contact with the inside
surface of the fitting. The clearance area is closed,
forcing the flux from either end of the joint. Be sure to
heat the entire circumference of the tube until the flux
begins to flow. Flux flow tells you that the tube has
expanded sufficiently, and signals you to proceed to the
second phase of heating. The flux flows freely shortly
after fluidity becomes apparent. At that time, direct the
flame to that portion of the fitting hub farthest from the
junction of the tube and the fitting. Sweep the flame
over the joint segment in a circular motion until the
brazing filler metal appears at the junction of the pipe
and fitting. At that moment, flick the torch away so that
the flame wipes toward the pipe. This completes one
segment of the joint. Repeat the procedure until all
segments are completed. A satisfactory joint shows a
continuous ring of filler metal at the end of the fitting.
The ring must be smooth and concave.
In the insert method, the filler metal will not leave
the recess unless both parts are at the proper bonding
temperature. One of the parts may be up to temperature
while the other is not. At that point, the filler metal will
not flow because it will be cooled or quenched by the
surface not yet up to temperature. Play the torch over a
2- or 3-inch section of the fitting. That will cause the
fitting to stretch or open up and let whatever remaining
flux is present run out. Hold the torch off the work and
the fitting will return to normal size and force the filler
metal to the edge of the fitting. You may be sure that a
good joint is formed when you can see the filler metal
at one or both edges of the joined area. Figure 9-9 shows
the step-by-step process of brazing by the insert method.
Figure 9-9.—Insert method of silver brazing.
The feed-in method, sometimes called the face-feed
method, is accomplished by feeding the filler metal by
hand into the area to be joined. Remember that the filler
metal always flows along a heated surface from the
cooler to the hotter section. In other words, the filler
metal flows toward the source of heat or to the point
where the heat is being applied. Feed the tiller metal to
the outer edge of the joint while you direct heat to the
inner edge of the joint. Figure 9-10 illustrates the
stepby-step technique for brazing a joint by the feed-in
The parts to be joined are cleaned and fluxed in the
same manner as in the insert method. When the parts
are fitted together, the clearance area is tilled with flux.
After aligning the parts, apply heat as previously
described. Then apply heat to the fitting or the inner
edge of the joint at the same time that the filler metal is
fed at the outer edge of the joint. The filler metal will
flow toward the hottest section. This means it will flow
through the joint toward the point at which heat is being
applied. It is left entirely to your judgment to decide
when both parts are properly heated and when to feed
the filler metal. It is also left to your judgment to decide
when enough filler metal has been fed into the joint to
completely fill the space between the two parts being
joined. Skillful torch manipulation is necessary to apply
heat to the proper point to cause the filler metal to flow
from the cooler to the hotter section. Filler metal visible
at the edge of the joint does not necessarily indicate that
the entire joint is filled.
The difference, then, between making a joint by the
insert method and by the feed-in method is in procedure.
When using the insert method, you heat a section and
remove the torch with a wiping motion, which causes
the filler metal to flow from the insert. In the feed-in
method, after you heat a section, you must direct the
flame to the inside edge of the joint while the filler metal
is being fed in at the outside edge of the fitting.
After the joint has cooled, clean the joint area with
a wire brush and warm water to remove flux, scale, and
discoloration. If flux is allowed to remain on the joint
area, it will cause corrosion and future failure of the
joint. After cooling and prior to performance of pressure
or leak testing, completed piping systems should be
cleaned and flushed to the extent necessary to ensure
satisfactory operation of the system and components in
service. Special cleaning, when required, will be
according to the specified requirements in the
shipbuilding, overhaul, or component specification.
Unless otherwise specified, all P-3a special category
systems (often referred to as P-3a critical systems) in
Figure 9-10.—Feed-in method of silver brazing.
submarines, as shown in table 9-5, will be flushed
according to one of the following procedures:
—Hot flush with fresh water for 1 hour while
ensuring that the temperature at any part of the system
does not go below 110°F.
Table 9-5.—Class P-3a Special Brazed Joint Categories
2.375” O.D. and Larger & above
300 psi
2.375” O.D. and Larger & above
300 psi
Steam and Steam Drain Sys
Sea Water Sys Subject to
Submergence Pressure
Missile Booster Suppression Sys
Hydraulic Sys
1.660” O.D. and Larger & above
600 psi
2.375 O.D. and Larger & above
600 psi
Lube Oil Sys
2.375” O.D. and above
2.375” O.D. and above
Flammable or Lethal Fluid Sys
(e.g., Gasoline, Cleaning Fluids,
JP-5, Fuel Oil, Oil Sys other
than Hydraulic, Lube Oil and
0.840” O.D. and Larger
Oxygen Sys
0.840” O.D. and Larger & above
10 psi
2.375” O.D. and Larger & above
10 psi
Air Sys (including compressed
gases-Nitrogen, Helium, and
Fixed CO2
0.840” O.D. and Larger & above
600 psi
2.375” O.D. and Larger & above
600 psi
Other systems where specified
0.840” O.D. and Larger
0.840” O.D. and Larger
1.315” O.D. and Larger
2.375” O.D. and Larger
Inspection Requirements: (See 7.3.1.)
Ultrasonic inspection is required on all brazed joints of sizes and pressures shown for the various categories in this table
except ultrasonic inspection is not required on freon (halocarbon) refrigerant systems.
NA = Not applicable
(1) Joints in systems, 0.840” O.D. and larger, subject internally to sea water at submergence pressure where failure of
the joint would result in direct internal flooding within the full and which normally operate at depths in excess of 200 feet.
(2) Joints in the following hydraulic piping having a system design pressure above 600 psi also require ultrasonic
a. Tubing and piping 0.830” O.D. and larger in supply mains which supply components in more than one compartment, and in the branch supply lines from these mains up to the first isolation valve in the branch.
b. Tubing and piping 0.840” O.D. and larger, failure of which could result in simultaneous loss of normal and
emergency modes of control for any steering or diving control service.
c. Piping, 0.840” O.D. and larger, in the emergency sea water valve control system necessary to ensure the integrity
of the independent system (this includes all joints from the hydraulic actuator for the sea valve to the isolation
valve(s) in the branch line(s) serving the flood control and normal operating station).
(3) Joints excluded from this category include those in segments of piping within their respective tanks, piping passing
through tanks which contain identical fluid, and all sounding tubes, air escapes, vents and overflow piping.
(4) This includes low pressure MBT blow piping external to the pressure hull which is designed for external
pressure greater than 600 psi.
—Conduct a hot recirculating procedure with fresh
water for a period of 1 hour for systems where such an
arrangement is feasible. Again the system temperature
must be monitored so that no part of the system falls
below 110°F. Following the recirculation, flush the
system with fresh water for 15 minutes at a minimum
temperature of 60°F.
Repeat this procedure continuously along the joint until
the entire seam has been completed.
Remember that silver brazing filler metal flows
along a sheet in the direction of the hottest point. This
point is usually where the torch flame is being applied.
Apply heat long enough to draw the filler metal through
the seam. Take care to avoid forming beads or globules
along the inside edge of the seam.
—Cold soak the system for 12 hours using fresh
water at a minimum of 60°F. At the completion of the
12-hour soak, flush the systems with fresh water at a
minimum of 60°F for 4 hours.
Repairs to or alterations of a piping system often
involve the disassembly of silver-brazed joints. For
operations of this kind, use a tip one or two sizes larger
than that used for brazing a similar joint. The fitting or
tube must be held securely in a fixed position before
heat is applied. With the exception of the initial
tube-heating phase, the same rotary torch manipulation
you used to make the joint is used to break the joint.
Cover the joint with flux and use it to gauge the
temperature. Add a little new filler metal while heating.
When the filler metal flows, pull the parts apart.
The description of the brazing techniques in the
preceding paragraphs apply specifically to joints
between tubes and fittings in piping systems. Except for
minor differences, the procedure is the same when
brazing sheet, strap, or bar stock. Here you probably
will use the feed-in method rather than the insert
method. Lap joints are used with material less than
one-eighth inch thick, while scarfjoints are usually used
when the section thickness is greater than oneeighth
inch. The following description points out the
difference between pipe brazing and seam brazing.
Fittings and valves are easily damaged by shock
when they are hot. Therefore, handle them carefully.
Piping and fittings removed from a system can be
cleaned, resized, and reused if they meet the following
inspection criteria (cracked piping and fittings must not
be reused):
Seam brazing requires some means for holding the
parts in position. Short pieces can be clamped or riveted
at the ends. Longer pieces are wired to size by using
wire clamps. After the parts are wired or clamped in
position, place additional flux along the outside of the
seam. Then, tack weld both ends of the seam. Make
additional tack welds along the seam approximately 8
inches apart. To make a tack weld, direct the flame to
both parts of the seam on a spot approximately 6 inches
in diameter. As soon as the flux becomes liquid in this
spot, direct the flame to the sheet forming the
underneath part of the seam. Place a layer of silver
brazing filler metal approximately 1 inch long on the
edge of the seam. Now direct the flame to the sheet
forming the upper part of the seam. This will draw the
silver brazing filler metal through the joint, completing
the tack weld. When all tacks are completed the seam
is ready for brazing.
Old flux and brazing alloy can be removed to the
extent necessary to facilitate a new joint
assembly. Do not use hand grinding to prepare
the inside diameter of a fitting for reuse. All
traces of tightly adherent brazing alloy need not
be removed.
After brazing alloy removal, the fitting must be
liquid penetrant inspected or visually inspected
at 5X magnification on both the inside and
outside diameter surfaces in areas that have been
heated to brazing temperatures for cracks.
The wall thickness of fittings must not be
reduced below the allowable minimum.
The seam is brazed in sections 4 or 5 inches in
length. Start the braze about 3 inches away from the tack
at the edge of the seam. Hold the torch so that the flame
is pointed in the direction that brazing is to be done.
Direct the flame first along one sheet and then along the
other until the flux becomes liquid. When this happens,
direct the flame to the sheet forming the underneath part
of the seam. At the same time, deposit a layer of filler
metal along the edge of the seam. Brazing filler metal
is drawn into and through the joint by a wiping motion
of the torch, forming the brazed joint in that section.
Brazing alloy rings may be slightly rounded on
the outer comers to fit insert grooves of reused
fittings to aid in the assembly of joints.
With the exception of copper-nickel alloy pipe,
pipe may be reused without inspection, unless
otherwise specified.
After sizing copper-nickel alloy pipe intended
for reuse, perform a liquid penetrant inspection
or visually inspect at 5X magnification the entire
filler metal has considerable strength when hot, and it
has the narrowest freezing range (solidifies quickest) of
the entire usable copper-zinc combinations. This is an
additional advantage, since a quick-freezing filler metal
has much better weldability than one that remains
mushy over a wide temperature range.
pipe periphery for a length of 2D (nominal) or 2
inches (whichever is less) plus the socket depth.
Reassemble piping and fittings by using the same
method you used for new installations. All silver-brazed
piping sections that have been removed for repairs, and
newly fabricated sections, must be hydrostatically
tested before they are installed. Procedures for
conducting hydrostatic tests will be discussed in
chapter 11.
Most of the commercial braze welding filler metals
are modifications of this 60/40 copper-zinc-zinc alloy,
with small additions of tin, iron, nickel, manganese,
silicon, and other elements.
Strong braze-welded joints depend on proper
preparation, the use of the correct technique, the
strength of the filler metal, and coalescence of the filler
metal and the base metal. The strength of a
braze-welded joint does not depend upon a thin film of
filler metal between close fitting surfaces as is true in a
silver-brazed joint. Heavy deposits of silver-base filler
metals have low strength values. However, heavy
deposits of copper-base braze welding filler metals
frequently attain strength comparable to welded joints.
Braze welding is used to make a groove, fillet, plug,
or slot weld using a copper-base alloy filer metal with
a melting point above 800°F but below that of the base
metal. The filler metal is not distributed in the joint by
capillary attraction. In the past, this process has been
called brazing. Earlier in this chapter, we said that all
brazing is done by capillary attraction. Braze welds are
made without melting the base metal, although some
fusion may occur between the filler metal and the base
metal. This method is very useful for repairing cast iron
and steel.
Adequate preparation, which includes thorough
cleaning, is essential in braze welding. Remove all
foreign matter such as oil, grease, and oxides. The metal
on the underside and on the top of the joint must be
bright and clean. If the parts to be joined or repaired are
less than one-fourth inch thick, it is not necessary to vee
the edges. Cross sections of base metal one-fourth inch
or larger must be beveled to about a 90-degree vee.
The fact that braze welds are made without melting
the base metal simplifies the welding procedure. Since
braze welding requires less heat, the speed of welding
is increased.
The lower temperatures required for braze welding
mean that preheating is also easier. As a rule, braze
welding operations can be done with only local
preheating; that is, preheating only that portion of the
part to be braze welded. This makes it possible to repair
broken castings and other parts in place, thus saving the
time and expense of disassembling and reassembling.
Coarse-grained soft castings are harder to tin than
close-grained castings. A cast-iron part that has been in
contact with fire will sometimes be difficult to tin. The
same is true of castings that have been exposed too long
to steam and oil at high temperatures. Also, it may be
difficult to tin castings that have been in salt water or
chemicals for some time. One way to make such pieces
easier to tin is to alternately heat and cool the casting.
When tinning is difficult, it may be necessary to remove
the affected surfaces of the metal so that it will take the
filler metal.
Braze welding is widely used to repair gray iron
castings. It is used not only to repair broken castings,
but also to rebuild worn parts, such as gear teeth or valve
disks and seats. You can also repair and rebuild pistons,
rotary valves, guides, and other sliding surfaces on
pumps, engines, and machinery.
When you have cleaned the parts, the next step is to
align them. Obviously, the parts must be kept in proper
alignment and kept that way during the brazing process.
You can do this best by using clamps and by tack
Braze welding should not be used to repair or
rebuild castings where the difference in color between
the filler metal and cast iron would be objectionable.
Nor should it be used to join parts that will be subjected
to temperatures above 650°F, or to repair working parts
or containers used in chemical processes.
In braze welding, a casting must be heated along the
line of the weld. This sets up strains caused by
expansion and contraction, unless the casting is
properly preheated. In a small casting, up to about a
hundred pounds, the heat from the torch is enough to
preheat the entire casting. Larger castings should be
The best filler metal for braze welding is a naval
brass that has a copper-zinc ratio of about 60 percent
copper and 40 percent zinc. This ratio produces the best
combination of high tensile strength and ductility. This
more thoroughly preheated. This relieves stresses,
speeds up the braze welding operation, and requires less
oxygen and acetylene.
Preheating can be done with a torch, or with an
improvised firebrick furnace covered with insulatingtype fire-retardant cloth. At times, castings attached to
a machine may be welded in place. These castings often
can be preheated if you play the flame along the line of
the weld and protect the surrounding surfaces with
insulating cloth. Large castings should be postheated to
relieve stresses. Flux is essential in braze welding with
an oxyacetylene flame for two reasons: (1) it removes
oxide that forms ahead of the welding zone due to the
oxygen in the air, and (2) it dissolves the oxides formed
in the braze welding operation. Use plenty of flux in the
tinning operation, but use flux sparingly to fill the vee.
When you see that more flux is required, add it carefully.
The puddle should not be made mirror clear, but it
should be left slightly clouded with oxide. Where the
braze welding is rapid, coat the rods entirely with flux.
If the operation is slow, as with heavy castings, dip the
hot end of the welding rod into the flux and add to the
puddle as required.
Use a slightly oxidizing flame for braze welding.
Make periodic checks to be sure that this adjustment is
maintained. A slightly oxidizing flame makes a better
bond between the filler metal and the base metal. It also
keeps a slight film of oxide over the puddle. This film
protects the weld metal from the oxygen in the air.
After the parts have been properly prepared—
cleaned, fluxed, aligned, and preheated if necessary—
they should be tack welded together. Heat the metal with
a torch at the point where the braze weld is to start. Play
the torch flame over the part to be heated, using a
circular motion. As the base metal gets hot, test its
temperature with a drop of metal from the welding rod.
When the base metal is at the right temperature, molten
filler metal spreads evenly over the surface. This
produces a tinning coat on the base metal.
You can tin the base metal in braze welding only
when the conditions are just right for it. If the base metal
is too cold, the filler metal will not run out and spread
over the heated surface as it should. If the base metal is
too hot, the filler metal will form little balls like drops
of water on a hot stove. If the temperature of the base
metal is right and the tinning is done properly, the
molten filler metal will spread over the surface like
water spreading over a clean, moist surface. Tinning is
the most important step in the braze welding process.
This free-flowing film of deposited filler metal forms
the intimacy of contact necessary for coalescence
between the base metal and the filler metal. When the
immediate area under the torch flame is tinned,
additional metal is added as necessary to fill the vee.
Tinning must, at all times, continuously precede filling
the joint.
As the tinning action is in progress, continue to feed
the brazing filler metal into the molten puddle to build
the weld up to the desired size. The puddle should be
small in size, but increased as it is moved forward, until
it completely fills the vee and a full-sized braze weld is
made. Be sure that the tinning action takes place
continuously, just ahead of the puddle. Good braze
welding makes one continuous operation of the tinning
action and the building up of the braze weld to the
desired size.
The inner flame cone is kept from oneeighth to
one-fourth inch away from the surface of the metal.
Usually the flame is pointed ahead of the completed part
of the weld at an angle of about 45°, with the puddle
under and slightly behind the flame. You vary the angle,
however, when welding in flat, overhead, and vertical
positions. Also, the angle will vary with the size of the
puddle being carried, the nature of the surface, and the
speed of welding. Braze welding can be done in any
position, but the flat position should be used if
Bright spots on the metal in the puddle mean that
oxides and impurities are present. They should be
worked out with the torch flame or with flux. Don’t use
too much flux; it is wasteful and prevents making the
best joint. Use just enough to get a good tinning action
between the filler metal and the base metal. The proper
rate of braze welding is controlled by the rate of tinning;
never allow the puddle to get ahead of the tinning action.
If it is necessary to deposit filler metal in layers, as
when braze welding heavy materials, the tinning of the
base metal is particularly important. If the tinning is
good and fusion between the layers is complete, a strong
braze weld is assured.
After you have finished the braze welding
operation, the internal stresses will need to be relieved.
To do this, play the torch over the weld and on either
side of the weld for several inches. The size of the weld
and the size of the casting determine the size of the area
that should be heated. Continue to heat until all sections
of the part have been brought to even heat. If the
repaired part is small, bury it in dry slaked lime. If it is
large, cover it with an insulating-type fire-resistant
cloth. Always cool the repaired part slowly. The part
should be protected from drafts and cold air, which
cause uneven cooling. Never subject a braze-welded
joint to stress until it has completely cooled.
two most important safety precautions in repair welding
operations are as follows:
Surfacing is a process in which a layer of some
special ferrous or nonferrous alloy is welded to the
surface of new or old parts. The purpose is to increase
their resistance to abrasion, impact, corrosion, and
erosion, or to obtain other properties. Surfacing is also
used to build up undersized or worn parts. In this latter
instance, the procedure restores the efficiency of
pistons, guides, shafts, and other parts. The filler alloy
used for such jobs is the copper-base alloy used for
braze welding. In fact, the technique is essentially the
same. A word of caution: COPPER-ZINC FILLER
SURFACE EXCEEDS 500°F. Steel parts subjected to
high stress should be built up or resurfaced only once.
Cast iron and copper-base alloys may be resurfaced as
often as necessary.
Figure 9-11 shows the principal steps used to build
up a worn steel piston with copper-base alloy. For this
kind of job, Machinery Repairmen will cut the grooves
and machine the finished job to size. Your job is to apply
the surfacing alloy.
Weld the rough-turned grooves first. Then, build up
the surface with one, two, or three layers of bronze as
required by the finished dimensions. When built-up
repairs are made on cylindrical objects, the work should
be set up to allow the surfacing operation to progress up
a slight incline of about 30°. When building up a thick
surface, it’s a good idea to do the job in several passes.
On the first pass, concentrate on tinning. On the
following passes, concentrate on good fusion between
the layers of surfacing alloy. Use flux sparingly after the
tinning pass or you’ll wind up with a porous weld. The
SPACES MUST BE VENTED. If not vented, they will
vent themselves in a drastic manner—by exploding.
Play safe by removing vent plugs or by drilling small
holes through which expanding gases may escape when
the part is heated.
plenty of ventilation and wear a respirator when you’re
working with brasses and bronzes, because they contain
up to 45 percent zinc.
A surfacing operation using a copper-base alloy
filler metal produces a relatively soft surface. Use other
types of alloys to produce a surface that is corrosionand wear-resistant at relatively high temperatures. Two
examples are facings for valve seats and disks used in
high-pressure steam lines.
While many rods and electrodes are manufactured,
only a few meet Navy specifications. Be sure your filler
alloys are approved by the Naval Sea Systems
Command for the work you are doing.
Three types of hard-surfacing materials are
generally used in the Navy. They are chromium-cobalt,
tungsten carbide, and iron-base alloys containing
manganese, chromium, carbon, nickel, and other
hardening elements. Of these, the chromium-cobalt
(MIL-R-17131) alloy is probably the most important. It
is used to repair disks and seats of high-pressure steam
system valves. At present, no electrodes meet the Naval
Sea Systems Command specification for this purpose.
Noncritical surfacing operations, that is, disks and seats
of valves manufactured from material other than
carbon-molybdenum or chromium-molybdenum
steels, need different materials. A MIL-E-19141
electrode or a 46R3C oxyacetylene welding rod may be
used if a hard surface is required. For critical carbon or
chrome-moly steel surfacing jobs, use a
chromium-cobalt rod applied with the oxyacetylene
Chromium-cobalt surfacing filler metal is an alloy
of about 60 percent cobalt, 30 percent chromium, 5
percent tungsten, and 5 percent other alloys, including
molybdenum and traces of iron. At room temperature
this alloy is about as hard as ferrous tool steels.
However, chromium-cobalt has the property to retain
its hardness at high temperatures. With the exception of
high-speed tool steels, common ferrous alloys do not
have this characteristic.
Surfacing alloys are usually applied so that the
material forms a thin layer over the base metal to which
Figure 9-11.—Surfacing a steel piston.
it is applied. The thickness of the deposit is usually from
one-sixteenth to one-eighth inch, is seldom over
one-fourth inch, and is generally deposited in a single
pass. Cleanliness is just as important for surfacing as it
is for braze welding. Scale, rust, and foreign matter must
be removed before surfacing to prevent the formation
of blow holes. If the surface of the base metal is clean
and properly prepared, then these three points are
important for a good hard-surfacing job using
chromiumcobalt ahoy: (1) flame adjustment, (2) base
metal surface appearance at the time the ahoy is applied,
and (3) surfacing ahoy application to the base metal.
When you are surfacing with chromium-cobalt, use
an oxyacetylene flame with an excess acetylene feather
about three times as long as the inner cone. Your success
depends upon the flame adjustment and the condition
of the base metal surface when the surfacing ahoy is
applied. Unless the excess acetylene flame is used, you
cannot develop the proper base metal surface condition,
and the surfacing ahoy will not spread over the surface
of the part.
The torch manipulation used and the surfacing
procedure itself are similar to those used in braze
welding. However, you need higher temperatures
(about 2,200°F) and tips one size larger than normal.
The heating phase of the surfacing operation is as
follows: With a sweeping motion of the torch, heat a
small area of the base metal until the surface takes on a
sweating appearance. Then, bring the end of the
surfacing ahoy into the flame and allow it to melt. Do
not stir or puddle the ahoy; let it flow. If the surface area
has been properly sweated, the ahoy will flow freely
over the surface of the base metal.
Good surfacing requires that you are able to
recognize a sweated surface. This sweating occurs when
the temperature of steel is raised to a white heat with a
carburizing flame. An extremely thin layer of the base
metal is carburized. The carburized layer has a lower
melting point than the rest of the base metal. As a result,
it becomes a liquid while the underlying metal remains
a solid. This liquid film provides the medium for
flowing the filler metal over the surface of the base
metal. The liquid film is similar to, and serves the same
purpose as, a tinned surface in soldering and braze
welding. The carburized layer is approximately 0.001
inch thick.
The surfacing ahoy is added to the carburized layer
at this time. It flows over the sweated surface and
absorbs the film of carburized metal. It is easy to see
this surface condition, but you should make several
practice passes before you try to surface a valve disk or
seat for the first time. Perfect the technique on scrap
metal before you try it on critical metal. A typical
Figure 9-12.—Surfacing a valve seat ring.
stepby-step application of chromium-cobalt surfacing
is illustrated in figure 9-12.
Tungsten-carbide is another surfacing material that
is applied with the oxyacetylene flame. This material is
used to build up wear-resistant surfaces on steel parts
that must withstand severe abrasion. It is used for such
noncritical applications as aircraft tailskids and earthand rock-moving equipment. The melting point of this
material is so high that it cannot be applied by gaseous
flame melting procedures. It is applied either in the form
of inserts, which are welded or brazed to the base metal,
or through the use of composite cast rod in which
tungsten-carbide particles are evenly distributed. When
this latter material is used, the surfacing technique is the
same as that used for oxyacetylene welding with a
slightly carburizing flame adjustment.
Iron-base surfacing alloys are used for a number of
applications requiring various degrees of hardness.
They can be applied by using either oxyacetylene or
electric arc welding. Hard-surface deposits are so hard
they cannot be filed or machined. They must be ground
to size and shape. Because of their extreme hardness,
they should be built up only slightly larger than the exact
size, to eliminate unnecessary grinding.
Figure 9-13 shows the method used to make lathe
and shaper tools by applying a surfacing ahoy. Other
uses for surfacing material aboard ship are lathe centers,
shear blades, and similar tools. When you prepare any
Figure 9-13.—Surfacing a lathe cutting tool.
features for feeding powders and a group of powdered
metal alloys developed especially for this process.
These powders are packaged in moistureproof bellows
modules to prevent contamination.
of these jobs for surfacing, be sure that the edges of
grooves, comers, or recesses are well rounded to
prevent overheating of the base metal.
Hard surfacing may be applied to all low-carbon
ahoy and stainless steels as well as to Monel and cast
iron. It is not intended for aluminum, copper, brass, or
bronze. Tool steels can also be surfaced, but they offer
difficulties caused by shrinkage and strain cracks. If tool
steels are surfaced, they should be in an annealed, not a
hardened, condition. If necessary, heat treating and
hardening can be done after the surfacing operation.
This process offers many advantages over the
conventional oxyacetylene and metal arc welding
processes. Absolute control of the thickness, width, and
deposition of the deposit can be attained by regulating
the amount of ahoy released, the rate of travel, and the
path of the torch. Deposits can be placed with pinpoint
precision because only the torch tip is used rather than
a tip and filler rod, or electrode holder and electrode.
This is especially true when it is used in confined and
hard-to-get-at spaces.
Surfacing with special alloys is not done as often as
brazing or braze welding. But when the technique is
used, it must be done perfectly, especially when
chromium-cobalt ahoy is applied to carbon or chromemoly valve parts for high-pressure, high-temperature
piping systems. On the whole, the silver brazing, braze
welding, and surfacing processes are important among
the welding procedures you will use in the welding
Powdered metal deposits are surface alloyed to the
base metal. They do not dig into the base metal and set
up fracture zones. There is also little or no problem with
underbead cracking. Deposit dilution, caused by base
metal pickup, is held to a minimum because of surface
The powdered metal flame spray process also has
advantages over the metal spray process. Although
fusion sometimes occurs when the metal spray process
is used, the deposits have, essentially, a mechanical
bond. On the other hand, powdered metal deposits
actually surface ahoy to the base metal and, as a result,
give a higher strength bond. Since the fuel gases propel
the alloy to the base metal surface, there is no
compressed air equipment that might offer additional
complications. Deposits made by the powdered metal
flame spray process also have greater density than those
made by the metal spray process. When you prepare the
base metal, you need to ensure only that the surface is
free of all dirt and grease. No time-consuming knurling
and roughing of the surface is necessary, as is required
with the metal spray.
Another welding process being used throughout the
Navy is the eutalloy process, which is most commonly
called the powdered metal flame spray process. This
process was developed by the Eutectic Corporation,
formerly the Eutectic Welding Alloys Corporation.
The powdered metal flame spray process can, and
should, be used alone for certain applications, but it is
not necessarily a separate, isolated technique. It
combines with, and works to supplement, conventional
oxyacetylene and electric arc welding, if overlays and
joining metals cannot be done by either of the two other
processes. It is very useful where the control of the
shape and thickness of the deposit helps reduce
machining time. This process is used for the repair of
both small and large parts. It is also used for surfacing
parts that are subject to abrasion, friction, and corrosion.
The powdered metal flame spray process uses the
low heat input principle. Control of the surface
temperature enables the powder to surface bond in the
shortest time. This eliminates unnecessary saturation of
the base metal with needless heat. Such overheating
does nothing to promote bonding, and usually results in
distortion and stresses in the base metal.
The torches used in the powdered metal flame spray
process are precision instruments, manufactured to very
close tolerances. They have very few moving parts and
require only routine cleaning and maintenance. These
torches are designed specifically for this process. They
should not be used for other gas welding applications.
The main elements of the powdered metal flame
spray process are a unique gas torch with special
Figure 9-14.—Powdered metal torch and accessories.
Figure 9-15.—Powdered metal torch with a water-cooled tip.
with three welding tips to help you weld a variety of
thicknesses of metals.
The torch shown in figure 9-15 is similar to the
torch in figure 9-14, but it has the added feature of a
water-cooled tip. This torch was designed especially for
overlaying surfaces in areas where there would be
danger of overheating the tip. Overheating of the torch
The torch shown in figure 9-14 is used to overlay
and join metals where there is no danger of the torch tip
overheating from reflected heat. The nucleus of the
torch is a precision forged chamber that contains the
vacuum mixer and the control valve. Internal design
prevents hazardous detonation and assures positive
control over the powder flow. This torch is supplied
Table 9-6.—Powdered Metal Alloys and Some of Their Uses
General Uses
Powdered Metal Ahoy
RC 55-62
Abrasion-resistant nickel-base ahoy for steel, stainless, nickel-base
alloys and cast irons. Corrosion resistant. Good hardness at high
temperature. Low coefficient of friction. Nonmachinable.
Ahoy for a thin, rough surface that will abrade, grip, or resist.
Uniformly distributed tungsten carbide grit firmly anchored in a hard,
corrosion-, and heat-resistant nickel-base matric. Nonmachinable.
RC 46-52
Cobalt-base ahoy overlay for steel, stainless, cast iron, and nickel
alloys. Corrosion and abrasion resistant. Holds hardness at high heat.
Low coefficient of friction.
RC 57-64
Severe abrasion-resistant ahoy overlay for steel, stainless steel, cast
iron, and nickel alloys. Tungsten carbide particles held in a nickel-base
matrix. Nonmachinable.
65,000 psi
High-strength, machinable ahoy for joining steels, copper, and
high-melting copper alloys. Copper-base ahoy deposits offer good
corrosion resistance and electrical conductivity. For fillet forming and
poor fit-up.
42,000 psi
High-strength, joining ahoy for copper and copper alloys. Copper-base
ahoy with good corrosion resistance and excellent electrical
conductivity in joints of proper clearance.
RC 36-42
Abrasion-, corrosion-, and heat-resistant nickel-base ahoy overlay for
steel, nickel alloys, cast iron, and stainless. Crack-resistant deposits, for
both overlaying and joining, are machinable.
High-strength, corrosion-resistant nickel-base ahoy for joining or
cladding steels, stainless, cast irons, and nickel alloys. Excellent
70,000 psi
RC 80-90
tip will cause the torch to backfire; the weld deposit will
be blown away, and the torch tip may be damaged.
Cooling water is circulated around the tip of the torch,
preventing reflected heat from affecting it. This torch is
often used to surface valve seats where the seat cannot
be removed from the valve body.
the optimum bonding and wetting of the deposit with
the surface of the workpiece.
These powders are contained in a bellows module
that locks directly into the torch. The unique bellows
action helps the flow of the powder through the torch.
The modules are capped when not in use to prevent
contamination from moisture or foreign matter.
Powdered metals are available to cover a wide
variety of applications. Table 9-6 contains some of the
different powders developed by the Eutectic Welding
Alloys Corporation. The ahoy chemistry and particle
size of each powder assures complete metal-melt during
passage across the torch flame. It also makes certain of
When you assemble the powdered metal torch,
hand tighten the large threaded nut on the mixing
chamber onto the torch body. (Synthetic O-rings are
achieve proper powder supply. Powder supply depends
upon base metal temperature. The powder may be
applied and fused simultaneously or it may be sprayed
to the work surface and then fused (wetted-out).
Whether you spray and fuse simultaneously or fuse after
spraying, do not travel forward with the torch, leaving
unfused powder behind.
used to ensure sealing of the seats; a wrench is not
required for tightening.) The double O-ring seats must
be properly seated for the torch to perform satisfactorily.
The O-rings or seats should be replaced if they are
damaged through wear or misuse. Next, thread on the
tip assembly and tighten it wrenchtight. The tip should
point downward for normal flat work. Remove the
closure from the bellows module, invert the torch, and
insert the module into the connective junction at the top
of the valve assembly. To do this, you will need to align
the lugs on the module with the openings in the junction.
Next, seat the module by turning it 90° clockwise; take
care that the connective junction on the torch is clean
and free of all foreign matter.
Once sufficient base metal temperature is reached,
you should usually make the balance of the deposit with
the torch lever in the fully depressed position. However,
you may experiment with the position of the lever to
ensure continuous operation. If necessary, you can
adjust either the needle valves or the regulators to get
better operating conditions. When making powdered
metal deposits, a slight weaving motion is generally
your best technique. The exact area and shape of the
surface where the deposit is being made will determine
the extent of the weaving motion. To ensure proper
fusion at the end of the beads, shut off the powder supply
by releasing the lever, and fill the final crater by using
previously deposited powder.
CAUTION: Do not turn the module beyond 90°,
as improper seating may occur. Connect the torch body
to oxyacetylene hoses which have standard 1/4-inch
The gas pressures used with the powdered metal
torch will vary according to the size of tip being used.
When using the larger tips, set the oxygen regulator
pressure from 25 to 30 psi and the acetylene regulator
pressure from 4 to 5 psi. When using the small tip, set
the oxygen regulator pressure from 15 to 18 psi and the
acetylene regulator pressure from 2 to 3 psi. When all
connections have been properly made and the
appropriate gas pressures set, the powdered metal torch
is ready for operation.
The actual distance between the torch tip and the
work surface will vary depending upon the type of work
and the operator of the torch. Usually, this distance will
vary from one-fourth to three-fourths inch. In some
joining applications, it may be best to hold the gap more
than three-fourths inch, depending upon joint design
and base metal thickness.
When you apply powdered metal to flat surfaces,
hold the tip vertical to the work, and keep the bellows
module as near perpendicular as possible. You can
rotate the tip assembly a full 360° to help you apply
powder in the vertical, horizontal, and overhead
positions, and the module will still be maintained in a
near perpendicular position. The thickness of the
deposits will depend on any or all of these five factors:
The powdered metal torch is lit in the same manner
as an oxyacetylene torch. Open the acetylene valve and
ignite the gas. Then, open the oxygen valve and adjust
the flame to suit the work. A neutral flame is generally
best. In the event that you experience difficulty in
maintaining the flame, adjust both the needle valves and
the regulators until the right combination is reached.
The smaller tip should be used for small flames.
(Cutting back the gases will choke the flame and cause
the tip to overheat.)
Size of tip
Quantity of powder fed into the flame
Speed of torch over work (slower speeds are used
for greater buildups)
After adjusting the flame for the alloy being used,
preheat the base metal, keeping the torch in constant
motion. The method and amount of preheat are
determined by the type of work. When color begins to
show in the base metal, concentrate the flame at the
starting area until a dull red color (for steels) is reached.
At this point, slowly depress the lever and observe the
passage of powder through the flame.
Temperature of base metal
Rate of (continuous or intermittent) power fed
into the flame
The torch is best operated with the lever fully
depressed, but you should experiment with the lever to
When you apply powdered metals, preparation of
the base metal is very important. The surface to be
overlayed should be free of all rust, oxides, or grease
and oil. The surface may be machined, filed, or cleaned
with emery cloth to ensure that it is clean.
Figures 9-16 through 9-21 show repairs being made
to an output shaft using the powdered metal torch. The
assembled output shaft unit is chucked up in a lathe as
true as possible. The thinnest possible machine-cut is
then made to remove the plating in the scored seal area
only (fig. 9-16). All grease, contaminants, and other
foreign matter have been removed with a good solvent.
A finished preparation lathe-cut of the scored area is
then made (fig. 9-17). The unit is then removed from
the lathe and the spline section is separated. The part is
now ready for the powdered metal overlay deposit.
The hollow shaft is slipped over a suitable mandrel
or other similar device for hand turning (fig. 9-18). The
best position of the shaft is horizontal, but the deposit
can also be made with the shaft in the vertical position.
The oxygen and acetylene pressures used should be
those recommended by the manufacturer for the tip you
are using. Use a neutral flame with a slight feather so
that when the powder feed lever is depressed a true
neutral flame is formed. Keep a minimum distance of
one-fourth inch between the flame cone and the work.
Figure 9-16.—Removing plating from the scored area of an
output shaft.
Figure 9-18.—Making a powdered metal overlay deposit.
Figure 9-17.—Final lathe-cut being made prior to making an
overlay deposit.
Figure 9-19.—Completed overlay deposit cooling prior to
Cobaltec 10091 or Borotec 10009. Follow the same
procedure regardless of the alloy powder used. After the
overlayed part has cooled, reassemble it to the spline
and chuck it up in the lathe for machine cutting or
grinding (fig. 9-20). Clean all overspray areas by
wirebrushing with a stainless steel brush.
Figure 9-21 shows the completed repairs and the
output shaft assembled and ready for reuse. Consider
factors such as corrosive media, wear patterns, base
metal, and desired hardness before you select the
powdered metal alloy. The repairs made to this output
shaft and similar repairs makes it unnecessary to have
to premachine for an undersize shaft, silver braze a
collar sleeve on the shaft, and remachine to the required
dimensions. The parts will last longer than the original
or new replacement parts, saving time, material, and
Figure 9-20.—Machining the overlayed section of an output
shaft to its original dimensions.
That way you will not obstruct the flow of the alloy
powder or overheat the oxidation of the base metal.
When you reach the proper preheat, depress the powder
feed lever to apply and fuse the powdered metal
simultaneously. Use gloves or pliers when you turn or
move the hot part.
To improve safety and to ensure proper operation
and care of the powdered metal torch, you should take
the following precautions:
Be sure all connections are tight. The connection
between the torch body and the mixing chamber
has neoprene scats. These should be tightened
only by hand.
Figure 9-19 shows the completed overlay being
cooled before it is machined. This deposit was made
with Bronzochrom 10185 and has a Rockwell “C” scale
hardness of 36. The finished deposit will work harden
in service. You can get a harder grind finish and specific
corrosion- and wear-resistant characteristics by using
Keep the tip orifice clean and unclogged at all
Use tip cleaners as often as necessary for proper
flame adjustment and powder passage.
Figure 9-21.—Repaired output shaft unit reassembled.
Soldering Gun
Never rub the tips against a fire brick to remove
clogged powder.
The soldering gun (fig. 9-22) operates from any
standard 115-volt outlet and is rated in size by the
number of watts it consumes. The guns used in the Navy
are rated between 100 and 250 watts. All good quality
soldering guns operate in a temperature range of 500°
to 600°F. The important difference in gun sizes is not
the temperature. Instead, it is the capacity of the gun to
generate and maintain a satisfactory soldering
temperature while giving up heat to the joint soldered.
The tip heats only when the trigger is depressed, and
then very rapidly. These guns afford easy access to
cramped quarters, because of their small tip. Most
soldering guns have a small light that is focused on the
tip working area.
Do not drill the tip orifice to a different size.
When changing from one type of powder to
another, be sure the torch is free of all previously
used powders.
Be sure the powdered metal module is properly
seated (90-degree turn only) and the connective
junction is free of all foreign matter.
Observe all standard safety precautions for
handling and using oxyacetylene equipment.
Handle all maintenance and repairs according to
the manufacturer’s instructions.
The tip of a soldering gun should be removed
occasionally to clean away the oxide scale that forms
between the tip and the metal housing. This increases
the heating efficiency of the gun. If the tip does get
damaged, replace it.
Soldering is used to join iron, nickel, lead, tin,
copper, zinc, aluminum, and many alloys. Soldering is
a simple, fast, and effective joining process. It is
particularly useful for securing electrical connections,
joining sheet metal, and sealing seams against leakage.
Soldered joints are not as strong as welded joints, and
should not be used where any great mechanical strength
is required. Soft solders always have melting points
below 800°F and below the melting points of the metals
to be joined.
A Hull Maintenance Technician seldom works on
electronic equipment. Still, you should remember never
to use a soldering gun on solid-state equipment. The
strong electromagnetic field surrounding the tip can
cause serious damage to solid-state components.
Soldering Irons
There are two general types of soldering irons in
use by the Navy. One is electrically heated and the other
is nonelectrically (externally) heated.
Soldering requires only a small amount of
equipment. For most soldering jobs, you will need only
a source of heat, irons, solder, and a flux. The sources
of heat vary according to the method used and the
equipment that is available. Welding torches, furnaces,
and other heating devices may be used. In most cases,
the heating devices are used to heat soldering irons,
which are then used to heat the surfaces and thus to melt
the solder. However, the heating devices are sometimes
used for the direct heating of the surfaces to be joined.
In this case also, the solder is melted by the heated
If you use a welding torch as a source of heat for
soldering, use it carefully. A welding torch gives out
much more heat than is actually required for soldering.
If you overheat the soldering coppers, you will have to
retin them and perhaps reforge them. Excessive heat
also may damage or warp the metal that is being joined
and may cause deterioration of the solder.
Figure 9-22.—Electric soldering gun.
The electric soldering iron (fig. 9-23) transmits heat
to the copper bit after the heat is produced by an electric
current that flows through a self-contained coil of
resistance wire; this coil is called the heating element.
Electric soldering irons are rated according to the
number of watts they consume when operated at the
voltage stamped on the iron, and the diameter of the
copper bit in inches (table 9-7).
There are two types of bits on electric irons. They
are plug bits that slip into the heater head and that are
held in place by a setscrew, and screw bits that are
threaded and that screw into or onto the heater head.
Some bits are offset and have a 90-degree angle for
soldering joints that are difficult to reach.
Electric iron bits must be securely fastened in the
heater unit. The bits must be clean and free of copper
oxide. Sometimes the shaft oxidizes and causes the bit
to stick in place. Remove the bit occasionally and scrape
off the scale. If the shaft is clean, the bit will receive
more heat from the heater element, and it will be easier
to remove when you need to replace the bit.
Figure 9-23.—Soldering irons
A nonelectric soldering iron (fig. 9-23) is sized
according to its weight. The commonly used sizes are
the 1/4-, 1/2-, 3/4-, 1-, 1 1/2-, 2-, and 2 1/2-pound irons.
The 3-, 4, and 5-pound sizes are not used in ordinary
work Nonelectric irons must be heated over a gas
Table 9-7.—Selection of Soldering Iron for Work to be Done by Copper Bit Size
Heated Irons
Heated Irons
Work to be done
Choice of Bit Dia.
Heat Rating Watts
Very light soldering.
1/4 to 7/16
Medium soldering of electrical
appliances and light manufacturing.
3/8 to 1/2
Fast soldering on radios, electrical
appliances, and light medium
3/8 to 9/16
Medium light soldering on tin ware,
plumbing, and wiring.
5/8 to 7/8
High-speed soldering of light tin
ware and small metal patterns.
5/8 to 1
Medium manufacturing such as
ventilation ducts and other shipboard
7/8 to 1-318
Heavy tin ware, metal patterns,
galvanized iron and copper.
1-1/8 to 1-3/8
Heavy ventilation ducts, tanks,
plumbing, and ship building.
1-3/8 to 1-7/8
Size of Bit, lb.
Filing and Tinning Copper Bits
New copper bits must be tinned (coated with solder)
before they are used. Also, bits must be filed and
retinned whenever they have been overheated or have
lost their coating of solder. The procedure for filing and
tinning a bit is as follows:
1. Heat the bit to a cherry red.
2. Clamp the bit in a vise, as shown in figure 9-24.
3. File the bit with a single-cut bastard file. Rear
down on the forward stroke, and release pressure on the
return stroke. Do not rock the file. Continue filing the
tapered sides of the bit until they are bright and smooth.
Figure 9-26.—Tinning a copper (solder placed directly on
CAUTION: Remember that the bit is hot! Do not
touch it with your bare hands.
4. Smooth off the point of the bit and smooth off
any sharp edges.
7. Apply solder to the bit until it is tinned. The
solder may be rubbed directly on the bit or it may be
placed on the cake of sal ammoniac.
5. Reheat the bit so that it will be hot enough to
melt the solder.
If sal ammoniac is not available, use rosin. Dip the
filed bit into a container of rosin, then apply the solder
as shown in figure 9-26.
6. Rub each filed side of the bit back and forth
across a cake of sal ammoniac, as shown in figure 9-25.
Commercially prepared soldering salts may also be
used to tin soldering bits. These salts are available in
powder form. Dissolve the powder in water to make a
solution, following the directions that accompany the
material. Dip the soldering bit into the solution, and then
apply the solder.
Cleaning Soldering Bits
Soldering bits should be cleaned just before they are
used. Sal ammoniac is usually used for this purpose.
Rub the copper on a cake of sal ammoniac or dip it into
a container of powdered sal ammoniac. Wipe it clean
with a cloth to remove all grams of sal ammoniac.
Another way to clean soldering bits is to dip the bit in
a solution made by dissolving a small amount of sal
ammoniac in water.
Figure 9-24.—Filing a soldering copper.
Most soft solders are alloys of tin and lead.
Occasionally, antimony, silver, arsenic, or bismuth are
added to give special properties to the solders. Solders
used for joining aluminum are usually alloys of tin and
zinc or of tin and cadmium. As mentioned before, soft
solders have melting points below 800°F and below the
Figure 9-25.—Tinning a copper (solder placed on a cake of
sal ammoniac).
Table 9-9.—Fluxes Used for Soldering Some Common Metals
Table 9-8.—Tin-lead Melting Points
Melting Point
(° F)
Muriatic Acid
(raw acid)
Zinc Chloride
(cut acid)
Phosphoric Acid
melting points of the metals being joined. Table 9-8
shows the melting points of most tin-lead solders.
Tin-lead solders are usually identified by numbers,
which indicate the percentage of tin and the percentage
of lead. The first number gives the percentage of tin, the
second gives the percentage of lead. For example, a
30/70 solder is an alloy of 30 percent tin and 70 percent
lead. Solders containing a high percentage of tin are
more expensive than those containing a high percentage
of lead. In general, the solders that contain a high
percentage of tin have lower melting points than those
that contain a high percentage of lead. Solders are
available in bars, wires, ingots, and powders. Wire
solder is available with or without a flux core.
Galvanized Iron
Dull Brass
Dull Copper
Black Iron
Tarnished Tin Plate
Tin Plate
Bright Copper
Terne Plate
Stainless Steel
which thorough cleaning is not possible, or where
corrosion would cause a serious problem.
The most commonly used corrosive fluxes are sal
ammoniac (ammonium chloride) and zinc chloride. The
fluxes are frequently used in solution or in paste form.
The solvent evaporates as the work is heated, leaving a
layer of solid flux on the work. At the soldering
temperature, this layer of flux melts and partially
decomposes, releasing hydrochloric acid. The
hydrochloric acid dissolves the oxides from the surface
of the work and from the solder.
Zinc chloride (sometimes called cut acid or killed
acid) should be made up in small amounts, as required
for use. To prepare zinc chloride, pour a small amount
of muriatic acid (the commercial form of hydrochloric
acid) into a container. Then, add pieces of zinc to the
muriatic acid until the liquid no longer boils and bubbles
when the zinc is added. The zinc and the acid enter into
a chemical reaction that produces zinc chloride and
hydrogen gas. When the liquid no longer boils and
bubbles, the reaction is complete and the liquid in the
container is no longer muriatic acid. Instead, it is a
solution of zinc chloride in water.
Strain the zinc chloride solution before using it as
a flux. Any solution that is not used immediately should
be stored in a tightly sealed glass container.
Observe the following precautions when you
prepare zinc chloride:
To make a satisfactory joint, you must be sure that
the metal to be joined and the solder are free of dirt,
grease, oxides, and other foreign matter that would keep
the solder from adhering to the metal. Fluxes are used
to clean the joint area, to remove the oxide film that is
normally present on any metal, and to prevent further
oxidation. Fluxes also decrease the surface tension of
the solder and thus make the solder a better wetting
agent. Table 9-9 shows the fluxes that are generally used
with some common metals.
Fluxes are generally classified as corrosive, mildly
corrosive, and noncorrosive. Corrosive fluxes have the
best cleaning action. However, any trace of corrosive
flux that remains on the work will cause corrosion of
the metal. Therefore, corrosive fluxes are not used for
soldering electrical connections, for other work in
Do not inhale the fumes given off by muriatic
acid or by the mixture of muriatic acid and zinc.
1. Select a soldering bit of the proper size and
shape for the work to be done. File and tin the
bit if necessary.
These fumes are dangerous to you and corrosive
to metals.
Do not prepare zinc chloride in a closed space.
Hydrogen gas is released as the zinc reacts
chemically with the muriatic acid. HYDROGEN
zinc chloride should always be prepared out in
the open or very near openings to the outside.
Also, take all necessary steps to prevent flames
or sparks from coming in contact with the
released hydrogen.
2. Heat the bit.
3. Position the work on a suitable support. When
a seam is to be soldered, position the work as
shown in figure 9-27 so that the seam does not
rest on the support. This will ensure that you
do not lose heat to the support.
4. Apply the flux with one or two strokes of a
brush or a swab.
Another type of corrosive flux that you may use is
known as soldering salts. Commercially prepared
soldering salts are usually furnished in powder form.
The powder is dissolved in water to make a solution.
When a corrosive flux has been used for soldering,
the flux residue should be removed from the work as
completely as possible. Most corrosive fluxes are
soluble in water. Wash the work with soap and water
and then rinse thoroughly with clear water to remove
the residue of corrosive fluxes. Do this cleaning
immediately after you finish soldering.
Mildly corrosive fluxes, such as citric acid in water,
are sometimes used for soldering. These fluxes have
some of the advantages of the more strongly corrosive
fluxes, and some of the advantages of the noncorrosive
fluxes. The mildly corrosive fluxes clean the surfaces
of the work but do not leave a strongly corrosive
residue. These fluxes are generally used for soldering
parts that can be rinsed with water after they have been
soldered or for work in which a mildly corrosive residue
can be tolerated.
Noncorrosive fluxes are used for soldering
electrical connections and for other work that must be
completely protected from any trace of corrosive
residue. Rosin is the most commonly used noncorrosive
flux. In the solid state, rosin is inactive and
noncorrosive. When it is heated, it becomes active
enough to reduce the oxides on the hot metal and thus
perform the fluxing action. Rosin is available in powder,
paste, and liquid forms.
Rosin fluxes frequently leave a brown stain on the
soldered metal that is difficult to remove. You can
prevent it to some extent by adding a small amount of
turpentine to the rosin. You can also add glycerine to the
rosin to make the flux more effective.
5. Clean the hot soldering bit with sal ammoniac,
as described earlier in this chapter.
6. Touch the solder with the hot bit so that a small
amount of solder flows over the tip of the bit,
as shown in figure 9-28.
7. Tack the pieces together, if necessary, so that
the work will stay in position while you are
Figure 9-27.—Soldering a seam.
When you are soldering with irons, follow this
Figure 9-28.—Picking up solder.
soldering it. Heat the spot by holding the bit
against the work. The metal to be soldered
must absorb enough heat from the bit to melt
the solder, or the solder will not adhere.
8. After the pieces have been firmly fastened
together, solder the seam. Hold the bit so that
one tapered side of the head is flat against the
seam, as shown in figure 9-27. When the solder
begins to flow freely into the seam, draw the
bit along the seam with a slow, steady motion.
Add as much solder as necessary, without
raising the bit from the work.
Figure 9-30.—Making solder beads.
9. To make the best soldered seams, solder
without lifting the bit from the work and
without tracing completed work.
10. Allow the joint to cool and the solder to set
before moving the joint.
11. If you used a corrosive flux, clean the joint by
rinsing it with water and then brushing or
wiping it with a clean, damp cloth.
Riveted seams are often soldered to make them
watertight. Figure 9-29 shows the procedure for
soldering a riveted seam.
Sometimes solder beads or solder shots are used to
solder square, rectangular, or cylindrical bottoms. To
make the solder beads, hold solder against a hot bit and
allow the beads to drop onto a clean surface, as shown
in figure 9-30.
Figure 9-31.—Soldering a bottom seam.
To solder the bottom seam with solder beads, first
flux the seam. Then drop one of the cold beads of solder
in the bottom of the container. Heat, clean, and dip the
soldering bit and place it against the seam, as shown in
figure 9-31. Hold the soldering bit in one position until
the solder starts to flow freely into the seam. Draw the
bit slowly along the seam, turning the work as you go.
Add more beads as you need them. Reheat the copper
as necessary.
Be very careful not to overheat an electric soldering
bit. Never go off and leave an electric soldering iron
plugged in. Overheating will probably bum out the
electrical element and damage the tinning.
Parts to be joined may be too large to be heated by
a soldering bit, or shaped in a way that would make rapid
Figure 9-29.—Soldering a riveted seam.
The solders used on aluminum alloys are generally
tin-zinc or tin-cadmium alloys. They are usually called
aluminum solders. Most of these solders have higher
melting points than the tin-lead solders used for
ordinary soldering. Both corrosive and noncorrosive
fluxes are used for soldering aluminum.
soldering difficult. In these cases, the soldering heat
may be provided by an oxyacetylene torch. Play the
flame of the torch on adjacent surfaces and then apply
the solder cold, in bar or wire form, to an appropriate
cross section of the area to be soldered. Flames should
not impinge directly on the fluxed surfaces. The heated
surfaces melt the solder, and the excess solder is
removed by wiping the joint with a damp cloth before
complete solidification of the solder.
The first step in soldering aluminum is to clean the
surfaces completely and remove the layer of oxide. If a
thick layer of oxide is present, remove the main part of
it mechanically by filing, scraping, sanding, or wire
brushing. You can use a corrosive flux to remove a thin
layer of oxide. The flux, of course, must be completely
removed from the joint after the soldering is finished.
Soldered joints in low-pressure, low-temperature
piping systems are sometimes made up by the torch
soldering method. If you must solder a joint near a
previously soldered joint, wrap the previously soldered
joint with a cool wet rag to keep the solder from melting.
After you clean and flux the surfaces, tin them with
aluminum solder. Apply flux to the work surfaces and
to the solder. You can tin the surfaces with a soldering
iron or with a torch. If you use a torch, do not apply heat
directly to the work surfaces, to the solder, or to the flux.
Instead, play the torch on a nearby part of the work and
let the heat be conducted through the metal to the work
area. Do not use any more heat than is necessary to melt
the solder and tin the surfaces. Work the aluminum
solder well into the surfaces. After the surfaces have
been tinned, the parts may be sweated together.
Sweating is commonly used to make electrical
connections. To make a sweated joint, clean and flux
each surface to be joined; then tin each surface. Hold
the pieces firmly together and heat the joint with a
soldering copper or with a torch until the solder melts
and begins to run out. Remove the source of heat and
hold the parts firmly in position until the solder has
completely hardened.
Soldering aluminum alloys is more difficult than
soldering many other metals because aluminum alloys
are always covered with a layer of oxide. The thickness
of the layer depends on the type of alloy and the
conditions to which it has been exposed.
The knowledge you have gained here will be
helpful to you. Silver brazing is a daily job for the Hull
Maintenance Technician. Braze welding, surfacing,
powdered metal flame spraying, and soldering are not
done as often as silver brazing, but they are done on a
frequent basis. Review each of the processes and then
practice them on scrap material. Knowledge is the first
step in being efficient in your job. However, practice is
also required.
Many aluminum alloys can be successfully
soldered, if you use the proper techniques. Wrought
aluminum alloys are normally easier to solder than cast
aluminum alloys. Heat-treated aluminum alloys are
extremely difficult to solder, just as are aluminum alloys
containing more than 1 percent magnesium.
Upon completion of this chapter, you will be able to do the following:
Identify the equipment of arc-welding systems and describe the procedures
and techniques used in shielded metal-arc welding.
Identify the different types and classes of bare and covered electrodes and
select the proper electrode and heat settings for typical welding.
Describe the safety equipment used in metal-arc welding and the correct
procedures for striking, establishing, maintaining, and breaking the arc.
Describe the characteristics of aluminum, their effect on its weldability, and
the procedures required to prepare aluminum for welding.
Recognize the basic techniques used in gas tungsten-arc (GTA) welding, and
describe the function and maintenance requirements of associated welding
Specify the methods used in making gas metal-arc (GMA) welds in various
positions, and describe some of the equipment used.
State the procedures to be followed in metal and carbon-arc cutting
Explain the procedures to follow in air carbon-arc cutting.
equipment and with the units of measurement used
with electricity. If you do not understand the terms
or units of measurement used in this chapter, study
the applicable parts of NEETS, modules 1 and 2.
Electric welding processes include shielded
metal-arc welding, shielded gas metal-arc welding,
stud welding, and resistance welding. This chapter
deals primarily with the first two processes; shielded
metal-arc welding and shielded gas metal-arc
welding. The other processes are summarized
briefly at the end of the chapter along with the arc
cutting processes.
Most of your metal-arc welding will be done by
This is a
the shielded metal-arc process.
nonpressure process, and the heat necessary for
coalescence is generated by an electric arc between
a heavily covered electrode and the base metal. The
arc develops an intense heat that melts the base
metal and forms a molten pool of metal. At the
To understand the operation of electrical
welding equipment, you must have a basic
understanding of electricity. In particular, you must
be familiar with the terms used to describe electrical
variable-voltage, dc generator welding unit, and (2)
the rectifier-type welding machine.
same time, the electrode tip is also melted, and
metal from the tip is carried across the arc into the
molten pool. The decomposition of the electrode
covering shields the molten metal from oxidation.
The temperature of the arc between the electrode
and the base metal is approximately 6500°F.
Variable-Voltage, DC Generator
Welding Unit
This unit consists of a dc generator driven by an
ac electric motor or by a gasoline or diesel engine.
The voltage produced by the generator usually
ranges from 15 to 45 volts across the arc, and the
current output varies from 40 to 400 amperes,
depending on the type of unit. In most units, the
voltage and ampere output of the generator is
controlled automatically by the self-regulating or
drooping voltage characteristics in the generator.
(An increase in current through the generator
results in a decrease in voltage.) In addition, the
generator output is manually controlled by one or
two manual adjustments.
The Navy has a wide variety of shielded
metal-arc welding equipment. In general, this
equipment is classified as either ac or dc; either
stationary or portable; and either single-operator or
multiple-operator equipment. In addition, it may be
classified according to the source of power and the
number of amperes delivered at certain arcvoltages.
The types of equipment available on any
particular ship or IMA will depend upon the kind of
electrical power available and the size and mission
of the ship. Since most ships are equipped with ac
power, we will discuss only the welding machines
that use an ac power supply or are diesel-driven.
Small combatant-type ships, such as destroyers, may
be equipped with two motor-driven, single-operator,
dc generator sets; whereas, cruisers and aircraft
carriers will have a larger number of these types of
welders. The motor-driven dc generator set uses an
ac power supply to run the motor, and the generator
provides dc welding current. Repair ships and
tenders may also be equipped with diesel-driven,
motor-generator sets as well as the electric
motor-generator sets.
Welding machines of this type may have single
or dual controls.
In the usual single-control
generator, output is adjusted by shifting the position
of generator brushes or by moving a portion of the
magnetic field structure of the generator. In the
usual dual-control generator, output is adjusted by
varying the generator shunt field strength and
varying the strength and direction of the series field.
The machine shown in figure 10-l is a dual-control
type fastened on an ordnance handling truck. A
ground plate is attached to the work to be welded,
and the electrode is clamped in the electrode
When an electric power supply is available,
welding generators are usually driven by an electric
motor connected to the generator by a flexible
coupling. Others are set up with the generator and
the motor on the same shaft. When an electric
power supply is not available, you must have a
All types of arc-welding machines require a
source of power that will allow you to strike and
maintain a stable arc suitable for welding. The
principal sources of power for shipboard welding are
as follows:
A dc generator with variable voltage
characteristics may be used in a single-operator
welding system. The generator is so designed that
it delivers a voltage high enough to start the arc and
reduce the voltage as required to maintain the arc
during the welding.
A rectifier may be used to convert ac to dc
for welding.
The power from these sources is used in various
types of welding equipment to provide the necessary
current. The basic types of welding equipment used
for shielded metal-arc welding are (1) the
Figure 10-1.—Variable-voltage dc generator welding unit
(dual-control type).
polarity (electrode positive), the greatest amount of
heat is concentrated on the electrode side of the
gasoline or diesel engine to rotate the generator. In
this case, the engine is equipped with a governor to
compensate for the varying loads imposed by the
Note that the concept of polarity applies only to
dc welding circuits. In ac circuits, the direction of
current flow is constantly reversing; therefore, an ac
circuit has no polarity affecting the operation of the
All dc generator welding units deliver either
straight or reverse polarity welding current. The
correct polarity is essential in metal-arc welding, so
let’s see what the term polarity really means. To
understand polarity, you must first have a clear
understanding of the welding circuit. The welding
circuit consists of (1) a source of welding current,
(2) a lead attached at one end to the power source
and at the other end to the electrode holder, and
(3) a ground lead or work lead attached at one end
to the power source and at the other end to the
work. In any electrical circuit, current flows only
when the circuit is closed. When a dc welding
circuit is closed, electrons flow from the negative
terminal, through the circuit, to the positive terminal
of the generator. The polarity can be changed by
use of the polarity switch located on the machine.
(See fig. 10-1.) If the machine does not have a
polarity switch, simply reverse the hookup of the
electrode lead and the ground lead, as shown in
figure 10-2.
The polarity recommended for a particular type
of electrode is specified by the manufacturer. If you
use the wrong polarity for a given electrode, the arc
will have a hissing sound and will be very difficult to
control. When the proper polarity is used, the arc
will have a sharp, crackling sound.
In general, reverse polarity gives a slower rate of
electrode burn-off, together with deeper and more
certain penetration. Reverse polarity also causes
greater fluidity and slower solidification of the weld
Joints in sheet metal are usually welded with
straight polarity. Reverse polarity is specified for
many other types of welds, particularly for welds
made in the vertical or overhead position.
Polarity is important because it determines the
location of the major portion of the welding heat.
About two-thirds of the heat of the arc is developed
at the positive pole. In straight polarity welding
(electrode negative), the greatest amount of heat is
concentrated on the work side of the arc. In reverse
Before placing any unit in operation, check the
nameplate data and the manufacturer’s technical
manual for exact instructions on setting up the unit.
Check the following points in particular:
1. If the generator is driven by an electric
motor, be sure that the power supply agrees with
the motor requirements. Never attempt to operate
a dc motor on ac power or an ac motor on dc
2. Check the motor supply cable and the fuses.
Make sure the wiring to the motor is large enough
to carry the load, and be sure the line fuses are
adequate. If you have any reason to doubt the
adequacy of the cable or the fuses, have the
equipment checked by an Electrician’s Mate.
3. On machines using an ac power supply for
the motor, ensure that the rotation of the motor is
in the indicated direction. You may reverse the
rotation of three-phase ac motors by interchanging
any two supply leads.
4. Before applying power to the motor, turn
the shaft by hand to make sure it turns freely.
Figure 10-2.—Reverse polarity and straight polarity.
Check to see that the generator and motor brushes
are in place and that they fit properly.
5. Before starting the motor, insulate the
electrode holder from the ground and attach the
work and electrode welding leads to the proper
generator terminals. On machines equipped with
reversing switches, connect the ground (or work)
lead to the terminal marked GROUND and the
electrode lead to the terminal marked
ELECTRODE. Then set the reversing switch for
the desired polarity. On machines not equipped
with reversing switches, connect the leads to the
terminals in the manner indicated on the nameplate
or in the manufacturer’s technical manual. To
change polarity on these machines, interchange the
Figure 10-3.—Paralleling connection for a single-operator
welding generator.
6. Adjust the welding current according to the
manufacturer’s instructions. Single-control machines
are designed to give adequate voltage at each
current setting. Dual-control machines have
separate voltage and current adjustments.
The overload device does not hold the
motor in the circuit.
Some values required for a given welding job
are beyond the capacity of a single-operator welding
generator. When this happens, the required current
can be obtained by interconnecting or paralleling
two single-operator generators (fig. 10-3). As a
rule, the sets that are paralleled should be of
identical rating. However, it is usually possible to
parallel sets of different ratings if you observe the
proper precautions. If sets with different current
ratings are paralleled, take special care to ensure
that the total load is divided in proportion to
machine ratings and that the current rating of
neither machine is exceeded. Paralleling
instructions are contained in the manufacturer’s
technical manuals furnished with your equipment.
The machine fails to hold its amperage.
The welding arc spatters excessively.
An Electrician's Mate is usually needed to
determine causes and to make repairs. However,
there are some things that you can and should do
before you call in the Electrician’s Mate.
If the machine fails to start, the trouble may be
an open or disconnected switch. You can check
switches yourself. If the machine runs but will not
generate current for the welding circuit, the motor
may be rotating in the wrong direction. You can
check the direction of rotation with the direction
arrow on the outside housing of the equipment. On
a three-phase motor, rotation may be changed by
interchanging any two of the motor power leads.
Have an Electrician's Mate change the motor power
leads if the rotation is wrong. If rotation is correct
and the machine still will not generate, the trouble
is elsewhere. You should call an Electrician's Mate
if the motor repeatedly cuts out of the circuit, or if
the machine does not hold its amperage after you
ensure that all welding cable connections are tight
and that the unit is properly adjusted.
All dc generator welders should be located in
clean, dry, well-ventilated places, away from acid
fumes or steam. Given proper care, the unit should
give many years of trouble-free service. Like most
mechanical devices, welding generators occasionally
fail to operate properly. Common problems include
the following:
The machine fails to start.
The machine runs but fails to generate
Excessive arc spatter may result from several
causes, such as arc blow, poor welding technique,
need not be so flexible as the cable that connects
the machine and the electrode holder.
incorrect current setting, incorrect electrode, or
incorrect polarity. Check the current output settings
and make any needed adjustment. If that does not
solve the spatter problem, check the polarity. Either
reverse the polarity of the generator or try an
electrode of the opposite polarity. Excessive spatter
should not occur if you use the proper welding
technique, the right polarity, and the correct current
output adjustment.
Two factors determine the size of the welding
cable that should be used: the amperage rating of
the machine, and the distance between the work and
the machine. If either amperage or distance is
increased, the cable size must also be increased. A
cable that is too small for the amperage used will
become overheated. A cable that is too small for
the distance between the machine and the work will
not carry enough current to the arc without
becoming overheated. On the other hand, the
larger sizes of cable are more difficult to handle.
The best size, therefore, is one large enough to
meet the manufacturer/NSTM requirements.
Most difficulties with generator welding units
can be avoided through routine maintenance and
periodic overhaul. Here again the Electrician's
Mate has primary responsibility. However, you are
responsible for keeping the outside of the
equipment clean. Once each month, blow the
outside and inside of the unit free of dust with
clean, dry, compressed air. At that time, oil the
wheel bearings on portable welding units. Operate
each of the machines for at least a few minutes once
a week. In addition to routine maintenance,
inspection, and testing, each machine should be
completely dismantled, thoroughly cleaned, and
overhauled as necessary every 2 years. Again, this
is a job performed by Electrician's Mates.
Instructions governing maintenance and overhaul of
electrical equipment, including welding machines,
are discussed in the NSTM, chapter 074.
As a rule, the cable between the machine and
the work should be as short as possible, preferably
one continuous length of cable. If it is necessary to
use more than one length of cable, join the sections
with insulated, lock-type cable connectors. Joints in
the cable should be at least 10 feet away from the
Most shipboard welding is done by the shielded
metal-arc welding process, and you will frequently
be responsible for seeing that the equipment is
properly set up and properly grounded. Incorrect
grounding permits the electric current to return to
the welding generator through the water, the ship’s
hull, and the piping systems. This may result in
electrolytic corrosion and cause serious damage to
the ship’s underwater body, shafting, and propellers.
Rectifier-Type Welding Machine
The rectifier-type welding machine operates
from an ac power source but delivers ac high
frequency and dc welding current. There are several
types of rectifier welders, but they are basically the
same. The majority of the units consist of three
major parts: (1) a transformer, to change the power
supply voltage (220 or 440 volts) to lower voltage
suitable for welding; (2) a movable core reactor, to
adjust the welding current; and (3) a rectifier cell
(copper oxide or selenium plates), to change the ac
to dc.
Grounding must comply with the
criteria of NSTM, chapter 074, volume 1.
The welding cables conduct the welding current
from the power source to the weldment and then
back to the source. They must be flexible, durable,
well insulated, and large enough to carry the
required current. Only cable that is designed for
welding should be used for welding. A highly
flexible cable must be used between the welding
machine and the electrode holder. The ground
cable, which connects the work and the machine,
Location of ground cables should be a major
concern when setting up welding machines. When
welding on systems, such as piping, pressure vessels,
or machinery, the ground-return cable connection
should be located as close to the work as possible.
This ensures that welding current does not flow
through bearings, threaded joints, and other joints
where arcing could occur. If arcing is allowed to
happen across bearings in motors, lathes, and other
up welding leads in three common situations. Note
that in each case, the only ground in the circuit is to
the ship where the welding is to be done.
similar components, they could be fused together.
Also, you should NEVER use electrical equipment
as a grounding circuit. They are not designed for
such use and the induced magnetic field produced
by welding could damage electrical equipment. You
should install ground-return cable connections no
further than 10 feet from your work.
When welding leads and grounds are arranged
as shown in figure 10-4, all the welding current flows
through the cables. When the welding equipment is
NOT correctly grounded, some or all of the welding
current returns to the generator by way of the water.
The portion of current that will flow through the
water will depend upon the particular grounding
error that is made.
The requirements for grounding welding
equipment vary slightly, depending upon the
situation. However, there are a few basic rules to
follow. Set up the equipment so that electrode and
ground leads are connected only to the vessel on
which welding is to be done. Secure the ground
lead to an integral part of the vessel, making a good
metal-to-metal contact. Be sure that both the
electrode and ground leads are thoroughly insulated
and that they are NOT in contact with water.
Figure 10-4 shows the correct methods for hooking
One very common error is to attach the ground
to one ship and then to weld on another ship. This
situation often occurs when a welding generator on
a repair ship or tender is used to weld on a ship
alongside. When this occurs, all of the welding
current returns through the water.
Figure 10-4.—Correct grounding procedure for metal-arc welding. (A) Arrangement for ships afloat. (B) Arrangement for a
single ship at a pier. (C) Arrangement for two ships at a pier.
Another incorrect grounding procedure occurs
when the ground is connected to both the ship on
which the generator is located and the ship on
which the welding is being done. In this situation,
part of the welding current returns through the
When grounding welding equipment, always
insulate the negative cable of the generator from the
ship on which the generator is located and run both
the positive and negative leads to the ship where the
welding is being done.
As an additional precaution, make a ship-to-ship
connection with a heavy copper cable. The cable
should be welded or bolted securely to bare metal
on each ship. If properly attached, the copper cable
will prevent most of the welding current from
returning through the water.
Figure 10-5.—Electrode holders.
This is an additional precaution, NOT
a substitute for correct use of the regular
welding grounds.
process. This includes various types of stainless
steel, high-tensile steels, and manganese steels.
Electrodes are also available for welding nonferrous
metals and alloys such as aluminum, copper, nickel,
and certain types of bronze and brass, some of
which were originally considered unweldable.
An electrode holder is essentially a clamping
device for holding the electrode securely in any
position. The welding cable passes through the
hollow, insulated handle of the holder. The
advantage of an insulated holder is that it may be
touched to any part of the work without danger of
short circuiting. Electrode holders permit quick and
easy change of electrodes.
Electrodes are manufactured for use with either
straight polarity, reverse polarity, or both. They are
also designed to be used in the different welding
positions. For example, an E6030 electrode is
designed for flat welding and is not suitable for
vertical or overhead welding positions. Electrodes
are available in a variety of diameters ranging from
one-sixteenth to three-eighths inch and in lengths
generally shorter than the rods used in gas welding.
Standard lengths are 9, 12, 14, and 18 inches. They
are also available in rolls for use in machine
welding. Some of these coatings may produce a
slag, but it is quite thin and does not act in the same
manner as the shielded arc type of electrode slag.
Electrode holders are made in a number of
different sizes and designs (fig. 10-5). Each holder
is intended for use within a specified range of
electrode diameters and within a maximum welding
current amperage. A larger holder isrequired when
welding with a machine having a 300-ampere rating
than when welding with a 100-ampere unit. A
holder will overheat if it is smaller than that
specified for use with a particular amperage.
Heavy Coated Electrodes
The surface of heavy coated electrodes is
comparatively thick. These coatings have been
designed to improve the physical properties of the
weld. They also control arc stability and, as a result,
increase the speed and ease of welding in the
vertical and overhead positions. These electrodes
Electrodes are manufactured in a variety of
metals and are available for use with any alloy that
is classed as weldable by the electric arc-welding
are manufactured by the extrusion, wrapping, or
heavy dipping processes, or combinations of these
The coatings used on these electrodes consist of
two basic materials: mineral coatings and cellulose
coatings. However, a combination of the two
materials may also be used. The mineral coatings
consist of metallic oxides such as clay, feldspar, and
titanium. The cellulose coatings consist of materials
such as wood pulp, sawdust, and cotton.
These heavy coating materials on the electrodes
accomplish the following:
Figure 10-6.—Welding with a heavy coated electrode.
—They produce a reducing or nonoxidizing
atmosphere, which acts as a shielding medium
around the weld deposit, excluding the oxygen and
nitrogen of the air.
Electrode classification tables are prepared and
published jointly by the American Welding Society
(AWS) and the American Society for Testing
Materials (ASTM). These tables are available in
booklet form from either of these organizations.
Electrodes are also classified with MIL SPEC
classification of MIL-E-22200 or other classifications
according to type and use of the electrode. To
illustrate these tables, the E60 series classifications
are shown in table 10-1. As shown in the table, the
electrode classifications contain the electrode
classification number, type of coating, welding
positions, and recommended current and polarity.
—They stabilize the arc and improve the flow of
metal from the end of the electrode to the puddle
on the work.
—The coating controls fluidity of the puddle and
shape of the bead by providing those ingredients
(oxides and silicates) that, when melted, form a slag
over the molten metal. This slag, being quite slow
to solidify, holds the heat and allows the metal to
solidify and cool slowly. This slow solidification
allows dissolved gases to escape and permits solid
impurities to float to the surface. The slow cooling
also has an annealing effect on the weld deposits.
To understand the significance of classification
numbers, consider the E6010 classification shown in
table 10-1. The E represents the word electric. The
first two numbers, 60, refer to the minimum tensile
strength in the nonstress-relieved (as welded)
condition, or 60,000 psi. The third number explains
the possible welding positions, such as 1 for all
welding positions (flat, vertical, overhead, and
horizontal); or 2, which designates a greater
restriction in choice by being usable only in the
horizontal and flat positions. Whereas, a 3 as the
third number indicates that these electrodes may be
applied in the flat position only. The fourth number
in the classification is used to indicate such things as
the proper power supply, quality, type of arc,
amount of penetration, type of flux, and so on.
—They control the physical properties of the
weld deposit and the composition of the deposit by
the addition of various metals and alloys to be
deposited during the welding process.
Figure 10-6 shows the arc characteristics when using
a heavy coated electrode.
Coated electrodes should be kept stored in their
original containers or in a dry area, such as holding
ovens, to prevent the coating from absorbing
moisture from the air, especially when the relative
humidity is very high. This is especially true of the
iron powder and low hydrogen coatings. An
increase in their moisture content will produce
unsatisfactory welds. In some cases, it is necessary
to dry out the electrode coatings by baking the
electrodes in a furnace or oven before using them to
Some electrodes are classified in five-digit
numbers instead of four. In this case, the first three
digits apply to the minimum tensile strength as
previously explained for the four-digit classification.
Table 10-1.—Electrode Classifications
Type of coating or covering
Capable of producing
satisfactory welds in
posit ions shown
Type of current
E60 Series.-Minimum Tensile Strength of Deposited Metal in As-Welded Condition 60,000 psi (or higher).
High cellulose sodium
F, V, OH, H
For use with dc, reverse polarity
(electrode positive) only.
High cellulose potassium
F, V, OH, H
For use with ac or dc reverse
polarity (electrode positive).
High titania sodium
F, V, OH, H
For use with dc, straight polarity
(electrode negative) or ac.
High titania potassium
F, V, OH, H
For use with ac or dc, straight
polarity (electrode negative).
Iron powder, titania
F, V, OH, H
For use with dc, either polarity or
Low hydrogen sodium
F, V, OH, H
For use with dc, reverse polarity
(electrode positive) only.
Low hydrogen potassium
F, V, OH, H
For use with ac or dc reverse
polarity (electrode positive).
Iron powder, low hydrogen
F, V, OH, H
For use with ac or dc, reverse
High iron oxide
H-Fillets, F
For use with dc, straight polarity
(electrode negative), or ac for
horizontal fillet welds; and dc,
either polarity, or ac, for flatposit ion welding.
Iron powder, titania
H-Fillets, F
For use with dc, either polarity, or
Iron powder, iron oxide
H-Fillets, F
For use with dc, straight polarity
(electrode negative), or ac for
horizontal fillet welds; and dc,
either polarity, or ac, for flatposit ion welding.
Iron powder, low hydrogen
H-Fillets, F
For use with ac or dc, reverse
High iron oxide
For use with dc, either polarity, or
The abbreviations F, H, V, OH, and H-Fillets indicate welding positions as follows:
F = Flat
V = Vertical
H = Horizontal
OH = Overheard
H-Fillets = Horizontal Fillets
For electrodes 3/16 in. and under, except 5/32 in. and
under for classifications EXX14, EXX1S, EXX16 and
In addition to the electrode classification
numbers, iron and steel electrodes may be identified
by a standard color code set up by the National
Electrical Manufacturers’ Association (NEMA).
This method of electrode identification uses a
two-color system consisting of a primary color
located on the end of the electrode and a secondary
color located near the top end of the electrode.
Figure 10-7 shows the location of the primary and
secondary on the end grip and center grip
electrodes. Part of the electrode color identification
table produced by NEMA is reproduced in table
Before beginning to weld, be sure you have all
the required equipment for welding and all the
equipment needed for your personal protection. Be
sure the welding machine is in good condition. Do
Figure 10-7.—Electrode color markings.
Table 10-2.—Color Markings For Electrode Identification
Primary colors
Mild steel and low alloys (See Note I)
Spot or
All position
fillets & flat
Flat position
No color
Special purpose
Hard surfacing (See Note II)
Mild steel for cast iron
0.40-0.70% Carbon
No color
Cast iron for cast iron
Brinell 200 min
051.0% Ni
Brinell 300 min
2.0-3.0% Ni
Brinell 400 min
12.0-14.0% Mn
Brinell 500 min
Ni Mn
Brinell 600 min
Ni Cr MO
Brinell 700 min
Ni Cr Cu
0.90-1.10% Carbon
Note I:
Electrodes listed with prefix letter are AWS designated grades.
Note II:
Hardness shall be determined as follows:
(a) Use a base plate of mild steel 5” square × 1” thick.
(b) Use 3/16” electrode.
Table 10-3.—Typical Current Ranges in Amperes for Electrodes
not attempt to use a welding machine until you are
entirely familiar with the procedures for setting it
and using it. Procedures for setting welding
machines vary according to the type of machine and
the manufacturer. Remember, you must set a
welding machine for the correct amperage, the
correct voltage, and the correct polarity.
There are a number of variable factors affecting
the machine setting. These include size and type of
electrode, thickness of metal to be welded, type of
joint, and skill and technique of the welder. With
these variables to be considered, it is apparent that
any set of current values could be merely
generalization. Current ranges as published by
different manufacturers vary considerably for the
same classification and size of electrode.
Table 10-3, compiled by the AWS, is included
for information, but the current values in this chart
are merely suggestive. A setting on the welding
machine within these ranges should be used only as
a preliminary setting since the table is intended to
cover all welding positions.
the electrode increased. With proper current and
electrode, you should get a smooth, uniform bead.
In addition to the major items of equipment that
we have considered so far, you may also need a
container for carrying electrodes, a chipping
hammer and a wire brush for removing slag from
the weld between passes, fillet weld gauges, a
hammer, a center punch, a scriber, a flexible rule,
and other supplementary equipment. Some welding
shops may have a welding positioner, a device fitted
with T-slots to help secure the work. also has a
system of hand-operated or power-operated gears
used to adjust the weldment so that all welds can be
made in the flat position. After all equipment has
been assembled and the machine has been properly
set, clamp the bare end of the electrode in the
electrode holder so that the entire length of the
electrode can be used without breaking the arc.
The proper welding current for a given set of
conditions can be determined from the degree of
electrode heat. If the electrode is too hot, then the
current is too high. Welds of good quality cannot
be made if the electrode overheats. In these
instances, the current must be reduced or the size of
The arc may be started either by the striking or
brushing method or by the tapping method. In
either case, the arc is formed by short-circuiting the
welding current between the electrode and the work.
The length of an arc is normally equal to the
diameter of the electrode’s filler metal. The heat of
the current at the arc melts both the end of the
electrode and the part of the work that it touches.
the base metal, and then slowly raise it a short
distance. If you raise the electrode too quickly, you
will lose the arc. If you raise it too slowly, the
electrode will freeze or stick to the base metal. If
this happens, you can usually free the electrode by
giving it a quick, sidewise twist. If you cannot free
the electrode in this way, remove the holder from
the electrode or stop the machine. Then chip off
the electrode with a chisel, to free it from the base
Figure 10-8.—Striking or brushing method of starting the arc.
To start the arc by the striking or brushing
method, bring the end of the electrode down to the
work in a continuous motion that describes the arc
of a circle. In other words, strike your arc in the
same manner that you would strike a wooden
match. As soon as the electrode touches the base
metal, check the downward motion and raise the
electrode to make the arc. The distance between
the electrode and the base metal should be about
equal to the diameter of the electrode. You can tell
when the distance is right by the sharp, cracking
sound the arc will make. Figure 10-8 shows the
striking or brushing method of starting the arc.
After the arc is struck, particles of metal melt
off the end of the electrode and are fed into the
molten crater of the base metal. The length of the
electrode is thus gradually shortened. Unless you
keep moving the electrode closer to the base metal,
the length of the arc will increase. If the electrode
is fed down to the plate and along the surface at a
constant rate, a bead of metal will be deposited or
welded on to the surface of the base metal. Before
advancing the arc, hold it for a short time at the
starting point to ensure good fusion and to build up
the bead slightly. Good arc welding depends upon
good control of the motion of the electrode down to
and along the surface of the base metal.
To start the arc by the tapping method, hold the
electrode at right angles to the work, as shown in
figure 10-9. To establish the arc, lower the
electrode and tap it or bounce it on the surface of
There are two correct methods for breaking an
arc. The most commonly used method is to shorten
the arc, and then quickly move the electrode
sidewise out of the crater. The other method is to
hold the electrode stationary until the crater is
filled, and then slowly withdraw the electrode.
When it is necessary to reestablish the arc (as
when the length of weld requires the use of more
than one electrode), the crater must be cleaned
before striking the arc. Strike the tip of the new
electrode at the forward (cold) end of the crater.
Figure 10-9.—Tapping method of starting the arc.
Move the arc backward over the crater, and then
move forward again to continue the weld. This
procedure fills the crater, and it prevents porosity
and slag.
arc. This sound should be heard all during the time
the arc is being moved along the joint.
The types of welds, the types of joints, and the
welding positions used in shielded metal-arc welding
are generally the same as those used in oxyacetylene
welding. The techniques, of course, are somewhat
different because of the different equipment
In arc welding, the position of the electrode in
relation to the joint being welded is a matter of
great importance. Increasing the electrode angle in
the direction of welding builds up a bead.
When welding a bead in the flat position (fig.
10-10), you should hold the electrode at a 90-degree
angle to the base metal. To get a good view of the
molten puddle, you may find it convenient to tilt the
electrode forward, in the direction of welding, to the
angle that is 5° to 15° off from the 90-degree angle.
Do not move the electrode from side to side as you
run a bead. To keep the arc constant, move it
forward just fast enough to deposit the weld metal
uniformly, and move it downward as rapidly as
A good weld bead made by the shielded
metal-arc welding process should have little or no
spatter on the surface of the plate. The arc crater
in the bead should be approximately the same size
as the electrode diameter or larger when the arc has
been broken. The bead should be built up slightly,
but should not have any metal overlap at the top
surface. There should be good penetration of
approximately one-sixteenth inch into the base
metal. Figure 10-11 shows properly made weld
beads in the flat position.
A butt joint in the flat position should be set up
in the same manner as for oxyacetylene welding.
Plates less than one-fourth inch in thickness can be
welded in one pass. They do not require any edge
preparation, but the pieces should be tacked
together to keep them in alignment. Use the same
electrode motion that you used for forming a bead
in the flat position. Plates one-fourth inch or more
in thickness require edge preparation by beveling or
The first bead or root pass is deposited to seal
the space between the two pieces of the joint at the
root. This bead must be thoroughly cleaned of all
slag before any other weld layers are made. The
second, third, and fourth layers of weld metal are
deposited using stringer beads in the order shown in
Use a short arc, about one-eighth inch in length,
and weld in a straight line at a constant speed. You
cannot judge the length of an arc by looking at it.
You will have to depend upon experience and the
sharp, cracking sound that is made by a good, short
Figure 10-11.—Properly made weld beads (flat position).
Figure 10-10.—Position of the electrode in making a bead in
the flat position.
view A of figure 10-12. Each bead must be cleaned
prior to depositing additional beads.
To ensure adequate penetration at the root, use
a backing strap when you make a butt weld in any
position. The backing strap should be about 1/2 to
1 1/2 inches wide and from 1/8 to 1/4 inch thick.
Figure 10-13.—Electrode work angle and lead angle.
The thickness and width of backing straps depend
upon the thickness of the plate being welded. You
should consult MIL-STD-22 for correct dimensions.
Tack weld the strap to the base of the joint and use
it as a cushion for the first layer of weld metal
deposited in the joint. Then complete the joint by
adding additional layers of weld metal in the regular
way. If the backing strap must be removed, do so
with a cutting torch or grinder. You must be
careful when cutting a backing strap with a torch so
that you do not gouge the plate or remove excess
material. If excess metal is removed, weld repair
will be required. The use of backing straps in
welding butt joints is shown in figure 10-12.
In making fillet welds, pay particular attention to
lead angles and work angles. In figure 10-13, the
work angle is the angle between the electrode and
the work in a plane at right angles to the long axis
of the joint.
The lead angle is the angle between the
electrode and the joint in the direction of the
welding. Work angles and lead angles for various
types of electrodes are usually specified by electrode
Figure 10-14 shows the fillet welding of a T-joint
in the flat position. The surfaces of the pieces to be
Figure 10-12.—Use of backing strips in welding butt joints.
Figure 10-14.—Fillet welding a T-joint (flat position).
Figure 10-15.—Order of making stringer beads for a T-joint
in heavy plate.
joined make a 90-degree angle with each other.
First weld a tack at each end to hold the pieces in
position. To make the fillet weld, use a short arc
and hold the electrode at a work angle of 45° to the
plate surfaces. Tilt the electrode to a lead angle of
about 15°. Light plate can be welded in one pass,
without any weaving motion of the electrode.
Heavier plate may take two or more passes, and you
must use a semicircular weave motion with the
second pass to get good fusion without undercutting.
To weld plate that is one-half inch or more in
thickness, use stringer beads in the order shown in
figure 10-15. Lap joints in the flat position are
made in the same way as T-joints, except that the
electrode should be held so as to form a 30-degree
angle with the vertical.
When welding in the overhead position, keep a
short arc of about one-eighth inch, hold the arc at
an angle of 90° to the base metal, and avoid
weaving. Butt joints in the overhead position are
most easily made with backing straps. If backing
straps are not permitted, the root can be welded
from the top of the joint. Each bead must be
cleaned and any rough places should be removed
before the next pass is made. Figure 10-16 shows
the correct electrode angle and the correct sequence
for running beads when making a butt joint in the
overhead position.
Figure 10-17 shows the fillet welding of a T-joint
in the overhead position. The welding should be
done with a short arc, using stringer beads. Hold
the electrode about 30° from the vertical plate, and
move it uniformly in the direction of welding.
Control the arc motion so as to get good root
penetration and good fusion with the side walls. If
the pool of molten metal gets too large and begins
to sag, shorten the arc and speed up the travel rate
of the electrode. Then return the electrode to the
crater, and continue the welding. On heavy plate,
several passes may be required to make either
T-joints or lap joints in the overhead position.
Make the second, third, and fourth passes of a weld,
like the one shown in figure 10-18, with a slight
circular movement of the end of the electrode. The
lead angle should be about 15°. Each bead must be
cleaned of all slag and oxides before the next bead
is added.
Welding in the vertical position is difficult
because molten metal tends to run down. A short
arc and careful control of voltage are particularly
important for welding in the vertical position.
Current setting (amperage) is lower for welding in
the vertical position than it is for welding in the flat
position. Also, less amperage is used for welding
down than for welding up in the vertical position.
When welding up in the vertical position, hold the
electrode at an angle of 90° to the vertical.
Welding with dc involves a special problem
known as arc blow (also known as magnetic arc
blow). It is important that you understand what arc
blow is and that you know how to recognize it and
what to do about it.
Figure 10-16.—Bead sequence and electrode angle for welding
a butt joint in the overhead position.
Arc blow is caused by distortion in the
field that surrounds a
takes control of the arc and causes it to pull this
way and that in a wild and uncontrollable fashion.
The situation must be corrected at the first sign of
trouble or the heat will become intense and the arc
will fluctuate wildly. In a very short time, the arc
will be lost, usually with an explosive burst that
carries away the molten metal of the weld. Arc
blow causes incomplete fusion and excessive spatter.
Arc blow can often be overcome. Following is
a list of some of the methods used most often by
experienced welders:
Changing the direction of the current
flow (Remember some electrodes can only
be welded with straight or reverse polarity)
Changing ground connections
Modifying the magnetic field with metal bars
across the weld groove
Working toward the ground from any bend
in the line of weld, or by tilting the
You will have to learn by experience which of
these measures works best under various conditions.
Distortion is a temporary or permanent change
in the shape or dimensions of a welded part as a
result of welding.
Expansion and contraction are the principal
causes of distortion in welding operations. During
welding, the metal is differentially heated and
subjected to drastic temperature gradients. It
becomes weaker and more easily deformed as it is
heated, and the tendency to distort is aggravated by
the degree of restraint at the weld joint.
Figure 10-17.—Fillet welding of a T-joint in the overhead
current-carrying conductor. The distortion occurs as
you approach any sudden turn in the welding; for
example, when you are welding on an I-beam or a
U-beam. When the field is distorted, a greater pull
exists on one side than on the other. When that
happens, the arc tends to blow out the side of the
electrode, consuming the covering faster on that
side than on the other side. The magnetic force
During all welding operations, the weld metal
and heated base metal undergo considerable
contraction when they are cooled to room
temperature. The surrounding cold metal offers
resistance to the shrinking of the heated area. The
weakness of the metal at elevated temperatures and
the small mass of heated metal compared to the
structure as a whole means that most of the
adjustment must be made by the weld metal.
Figure 10-18.—Welding in the vertical position.
When the part being welded is free to move,
distortion will be caused by contractual stresses.
Distortion may be prevented by the restraint of jigs,
structural rigidity, or the support of previous
welding. Under such conditions, you may expect
residual stresses up to the yield point of the metal.
If the required plastic flow exceeds the metal’s
capacity to flow, cracking may result. When a bar
of steel is heated thoroughly and uniformly, it will
expand in all directions. If it is allowed to cool
evenly, and without restraint of any kind, it will
contract to its original shape and size. On the other
hand, if the bar is restrained in any way during
heating, it will not be able to expand in the direction
of the restraint. For example, a metal bar placed in
a vise so that the jaws close against the two ends, as
shown in figure 10-19, cannot expand towards the
two ends. Any expansion would have to be lateral.
When it contracts upon cooling, however, there is
no restraint and it will contract in all directions. It
does not return to its original shape and size
but becomes shorter and thicker, as shown in
figure 10-19. Thus, a return to an original shape
and size is possible only when a part is free to
expand and contract freely and without restraint.
Distributing and balancing the forces and
stresses produced by weld shrinkage by
special welding techniques and sequences
If a bar is heated over a small area, the
expansion will be local and uneven. The mass of
surrounding metal will not expand, and tends to
prevent expansion of the heated metal in all
directions except upon the surface. Consequently,
when the yield point has been reached, the metal
becomes permanently deformed. When the bar
cools, it does not return to its original form, and
distortion results.
Forcibly restraining the parts being joined
from movement during welding by suitable
jigs and fixtures
The factors governing distortion are the
resistance of the structure to the free contraction of
the weld metal; the temperature gradient, which is
determined by the rate at which heat is applied and
the rate at which heat is conducted away from its
point of application; the coefficient of expansion of
the metal, which determines the total amount of
plastic movement; and the yield strengths of the
base and weld metal, which limit the residual forces
that can exist within the structure. Generally
speaking, there are six basic means of controlling
Stretching the metal, preferably while still
hot, by a series of hammer blows (peening)
Selecting the joint and the geometry of the
joint selected
Selecting the welding process
Selecting the weld joint bead procedure
Preheating involves raising the temperature of
the base metal or a section of the base metal above
the ambient temperature before welding. Preheat
temperatures may vary from as low as 60°F to as
high as 600°F for highly hardenable steels and
1200°F for ductile cast iron.
Preheating is a very effective means of reducing
weld metal and base metal cracking. Preheating
may improve weldability generally, but has two
major beneficial effects: it retards the cooling rates
in the weld metal and heat-affected base metal, and
it reduces the magnitude of shrinkage stresses.
However, when you are welding quenched or
age-hardened materials, the effects of preheating
can be detrimental unless they are controlled within
allowable limits.
In many operations, the temperature to which
the base metal is heated must be carefully
controlled. The best means of control is to heat the
part in a furnace held at the desired temperature, by
electric induction coils, or by electric resistance
heating blankets. In these methods, temperature
indicators are attached to the part being preheated.
Figure 10-20 shows electric induction coils set up for
preheating pipe prior to welding.
Figure 10-19.—Dimensional changes due to restrained
expansion and unrestrained contraction.
When using the oxyacetylene torch for
preheating, it is important to prevent localized
overheating and deposits of incomplete combustion
of gases on the surfaces of the joints of areas to be
welded. Temperature-indicating crayons that melt
at known temperatures are used for measuring the
temperature of the preheated part.
conductivity of iron is 50 percent less than at room
temperature. At 1472°F, the thermal conductivity of
many carbon steels is approximately 50 percent less
than at room temperature. Low thermal
conductivity ensures slow cooling rates because the
heat is transferred from the welding zone at a lower
Distortion, weld metal and base metal cracking,
and porosity may be eliminated or reduced by an
appropriate modification of the welding technique
and sequence. Certain sequences, such as backstep,
cascade, block, and wandering, minimize cracking
near the bond and are used to advantage in poor-fit
work. Whenever possible, welding should proceed
toward the unrestrained end of a joint, because free
movement of the parts will reduce the danger of
weld metal cracking.
Figure 10-20.—Electric induction coils set up for preheating
Cooling rates are usually faster for a weld made
without preheat. The higher the preheating
temperature, the slower the cooling rates after the
weld is completed. The temperature gradient is
reduced and, in the case of iron, the thermal
conductivity is decreased. At 1100°F, the thermal
When postheat is applied immediately to a
completed carbon steel or low-alloy steel weld, it
will retard cooling, minimize the formation of
underbead cracks, and slightly temper the structure.
Figure 10-21 shows postheat being applied to a
welded pipe, using electric induction coils.
Although postheat can prevent cracks, it cannot
remove cracks or porosity. Very highly hardenable
Figure 10-21.—Postheating welded pipe with electric induction coil equipment.
AWS because carbon dioxide is used as a shielding
gas when welding mild steel by the GMA process,
and carbon dioxide is not an inert gas.
steels should be transferred directly to a stress-relief
furnace without loss of preheat.
The peening of weld metal helps minimize
cracking of weld metal and reduces distortion
because it distributes the residual stresses created by
A big increase has occurred in the use of the
GTA and GMA processes for all types of structural
and piping systems. This is especially true in
aluminum fabrication. For that reason, we have
given special attention to these two processes. Our
discussion includes basic information on the
characteristics of aluminum that affect its
weldability, as well as on the effect of heat on the
aluminum part being welded. The importance of
surface preparation is explained. Detailed
information is given on both the GTA and GMA
processes. Practice exercises are provided to help
you develop techniques in various operations used
in each process.
Various specifications and codes require that the
first and last layer of weld metal not be peened.
Peening of the first layer could pierce the weld or
displace the members being welded. Peening of the
last layer can cause brittle fractures due to the cold
working of the weld metal. Use peening on each
weld bead or layer except the first and last. The
effectiveness decreases as the thickness of the bead
or layer increases. Peening becomes of doubtful
value for deposits on one-fourth inch or thicker,
except in special instances where the rigidity or
weight of the weldments permits the use of heavy
Selection of the arc-welding method to use on
aluminum depends largely upon the individual
application. You need to consider thickness; design
of the parts, components, or assemblies; and
available equipment. The best welding methods for
aluminum are the GTA and the GMA processes.
Both use noncombustible gas (argon, helium, or a
mixture of gases) to keep air away from the arc and
molten weld pool and to eliminate the need for a
welding flux. The gas shield is transparent; the
welder can see the fusion zone and make neater and
sounder welds. Aluminum can be welded in any
position by either method.
Peening equipment should be selected with care.
The hammer, pneumatic tools, and so on, should be
heavy enough in striking force to be effective
without producing excessive work hardening, but not
so heavy that bending moments are involved or
cracks produced in the weld.
The general causes of weld metal cracking, base
metal cracking, porosity, and inclusions are outlined
in table 10-4.
This process uses a shielding gas to protect the
electrode, arc, molten weld metal, and weld area
from exposure to the atmosphere. The shielding gas
is noncombustible and may or may not be inert
(chemically inactive).
The electrode may be
nonconsumable, or it may be a consumable wire
electrode that is fed automatically into the weld.
The GTA process is best for welding aluminum
sections less than one-eighth inch in thickness. This
method can also be used on heavier sections, but
the GMA process is usually chosen for its higher
welding speed and economy.
There are two different types of gas shielded-arc
welding processes. One is the gas tungsten-arc
(GTA) process, which uses a nonconsumable
tungsten electrode. The other is the gas metal-arc
(GMA) process, which uses a consumable wire
electrode that is fed automatically into the weld.
The factors that affect the welding of aluminum
and the properties of aluminum weldments include
melting point, thermal conductivity, thermal
expansion and contraction, oxidation, gas porosity,
and the effects of welding.
General Considerations
Pure aluminum melts at 1210°F, and weldable
aluminum alloys start to melt at 1050°F. This
compares with steel, which melts at about 2800°F
and copper at about 1980°F. Unlike these metals,
These two processes were formerly known as
tungsten inert-gas (TIG) welding and metal inert-gas
(MIG) welding. The names were changed by the
Table 10-4.—Causes and Cures of Common Welding Problems
there is no color change in aluminum during
heating. However, it is possible to know when the
aluminum is near its melting point and at welding
temperature by watching the weld pool. The GTA
weld pool, for example, develops a glossy
appearance, and a liquid pool or spot forms under
the arc when the metal becomes molten.
Aluminum conducts heat three times faster than
iron, so you need a higher heat input to weld the
aluminum. On the other hand, copper has a higher
thermal conductivity than aluminum; therefore, less
heat is required to weld aluminum than copper. It
is usually helpful to preheat heavy sections of
aluminum to reduce heat loss and, when using the
GTA process for joining such sections, to get better
welding results.
Aluminum welds decrease about 6 percent in
volume when solidifying from the molten state. This
contraction may cause excessive weld joint distortion
unless correct allowances are made before welding.
Thermal expansion of aluminum is
approximately twice that of steel and one-third
greater than copper. The surrounding surface
expands due to the heat of welding. Thermal
expansion of the adjacent aluminum may reduce the
root opening on butt joints during the welding.
Then, when the metal cools it contracts. This
contraction, coupled with shrinkage of filler metal
on cooling, may put the weld in tension and cause
cracking. Excessive restraint of the component
sections during cooling of the weld may also result
in weld cracking.
Speed is also a factor in preventing distortion.
Welding at a slow rate may cause greater area
heating, thus creating more expansion and
subsequent contraction.
Weldable aluminum alloys are of two types: the
work-hardenable alloys, such as EC (electrical
conductor grade), 1100, 3003, 5052, 5083, and 5086;
and the heat-treatable alloys, such as 6061, 6062,
6063, and 7039.
Although alloys in the 2000 and 7000 series are
also heat-treatable, most of them are not
recommended for arc-welded fabrication because
weldments are low in ductility. Better properties
are obtained with the resistance-welding method. A
notable exception is alloy 7039, now employed for
armor plate and other critical applications. Welding
qualities of alloys in the 2000 and 7000 series with
either resistance or GMA processes are excellent.
As-welded (GMA) strengths are upward of 48,000
psi, and ductility of these welds ranges from 8 to 12
percent elongation, in 2-inch increments.
Mechanical properties can be improved in
heat-treatable alloys by heat treatment at
temperatures above 900°F, followed by a
low-temperature aging treatment above 300°F.
Aluminum alloys lose hardness and strength
when reheated to high temperatures. When heated
above 900°F, the aluminum alloys revert to the
annealed condition almost immediately. The degree
of loss is a function of time and temperature. We
mentioned earlier that the weld metal is over 1050°F
when deposited; therefore, welding causes some
annealing of the parent metal. With the
heat-treatable alloys, welding also lowers the
ductility of the joint.
Preheating is necessary if the mass of the parent
metal causes heat to be conducted away from the
joint so fast that the welding arc cannot supply the
heat required to produce fusion. Insufficient heat
causes poor fusion of the weld bead and inadequate
melting of the parent metal. Preheating of the parts
being joined helps to produce a satisfactory weld,
reduces distortion or cracking in the finished
product, and increases welding speed.
Preheating is necessary in GTA welding of heavy
plate. For the heat-treatable alloys, such as 6061,
preheat should be used carefully. Too high a
temperature or too long a preheat period can
decrease the as-welded strength of the joint.
Recommended preheat temperatures for various
thicknesses of aluminum plate and tube are shown
in table 10-5.
In GMA welding, preheat is seldom required
regardless of plate thickness. This is one advantage
of the GMA process over GTA. Another advantage
is the greater welding speed of GMA.
Residual stresses created in aluminum alloy by
the heat of welding may become excessive, due to
the total amount of heat input, thickness of metal,
and design of the weldment. In extreme cases, such
stresses may cause early failure of the weldment.
One common method of modifying residual stresses
is by peening (localized working of the metal by
hammering) to effect limited distribution of the
stresses. However, peening usually is not advisable
on thin sections. For these and certain other cases,
stress relieving by thermal treatment is
recommended, where required.
All aluminum alloys can be completely annealed
by heating them to the proper temperatures for
specified periods of time. Annealing of the metal
relieves all residual stresses. The temperatures
required for substantial stress relief have an adverse
effect on the mechanical properties. This may lower
the resistance to corrosion in some alloys.
For aluminum-magnesium alloys (5000 series),
high residual stresses may be reduced by heating the
Table 10-5.—Preheat Temperatures for Welding Sheet, Plate, and Tubular Aluminum Sections (Butt Joints)
Tubular Sections
Approximate Preheat Degrees F
Outside Diameter
Wall Thickness Inches
Sheet and Plate
Approximate Preheat Degrees F
*Not recommended
Note: These preheat temperatures are only for use as a guide. Most weldors prefer to increase the
welding current and thereby avoid preheating. Preheating is another operation and increases
overall costs. Also, if welding the heat-treatable alloys such as 6061, it should be realized that
the temperature and length of preheating time can affect the as-welded strength of the joint. It
is seldom necessary to preheat when using the GMA process.
alloys at temperatures below 650°F, the temperature
for complete annealing. The principal limitation on
post-weld heating is whether the weldment can fit
inside the available oven. Heating the entire
weldment in a furnace is recommended. Local
heating for stress relieving is effective in some cases,
but only where testing or performance data proves
its effectiveness.
2400°F above the melting point of pure aluminum.
Temperature differential allows the aluminum to
melt before the oxide film. When this happens, the
film prevents fusion between the filler metal and its
base plate. Therefore, the oxide film must be
disrupted or removed by a chemical cleaner, flux,
mechanical abrasion, or by the action of the welding
The aluminum-magnesium alloys (5000 series)
can usually be stress relieved by post-weld heating
them at 450°F for approximately 4 hours. As
previously mentioned, complete annealing is
achieved upon heating these alloys to 650°F.
Cooling rate is unimportant.
Particles of oxide entrapped in the weld will
impair ductility of the weldment. The joint should
be cleaned with a stainless-steel wire brush
immediately before welding to reduce the oxide
The GTA and the GMA welding processes have
a major advantage over other methods, in that no
fluxes are required. The action of the welding arc
breaks up the oxide film. The noncombustible gas
Aluminum and its alloys rapidly develop an
oxide surface film upon exposure to air. This oxide
has a melting point in excess of 3600°F or about
shield envelops both the arc and weld pool,
preventing oxidation from recurring while the metal
is molten.
Molten aluminum readily absorbs available
hydrogen. When the weld pool solidifies, most of
the hydrogen is released because it is practically
insoluble in solid aluminum. This released
hydrogen may become entrapped and cause porosity
in the weld, which may impair its strength and
ductility. Also, hydrogen may get into the molten
weld metal from surface oils or from moisture on
the filler wire. To reduce weld porosity, the metal
surfaces must be carefully cleaned and care must be
taken to maintain the cleanliness of the filler wire
supplied by the manufacturer.
Cleaning the surfaces to be welded is of major
importance in all aluminum joining, regardless of
the welding process. This cleaning should be done
just before welding. Cleanliness cannot be
overemphasized. Oxide, grease, or oil films
remaining on the edges to be joined will cause
unsound welds. Unsoundness (porosity caused by
gas, dross inclusions, ships, and so on) reduces the
mechanical and electrical efficiency of the weld.
Mildly alkaline solutions, and commercial degreasers
that do not produce toxic fumes during welding, are
used to remove surface contaminants before
welding. One common method of cleaning is for
the welder to wipe the edges of the joint with a
cloth that has been dipped in a solvent, such as
alcohol or acetone. All welding surfaces should be
dried after cleaning to prevent porosity in the weld
metal. Avoid use of carbon-chlorine solvents.
Figure 10-22.—Recommended joint designs for common
thickness of plate.
The joint design and root openings required for
GTA welding are determined by the thickness of the
aluminum to be joined and the structural
requirements of the weldment. Design varies from
a square butt for one-eighth inch sheet to a
45-degree minimum included-angle vee joint for
one-half inch or thicker plate. For tubular sections
having a wall thickness greater than one-eighth inch,
the edges should be beveled with a minimum
60-degree included angle and have a zero to
one-sixteenth inch square butt lip. Recommended
joint designs for common thicknesses of plate and
pipe are shown in figures 110-22 and 10-23. For
one-eighth inch thick and up, some root opening is
recommended to ensure complete penetration.
Oxide films should be removed from the surface
of the aluminum by a suitable abrading process such
as brushing with a clean, stainless-steel wire brush
immediately prior to welding. If you are ever in
doubt whether to wire brush, DO IT. Black,
sooty-surfaced welds mean insufficient brushing.
The joint design and root openings required for
GMA welding are determined by metal thickness
and structural requirements as in GTA welding.
Aluminum sheet up to one-fourth inch thick can be
welded manually with complete penetration using a
square butt design. For manual welding, material
greater than one-fourth inch thick may have a
Preparing Aluminum for Welding
The choice of joint design for welding aluminum
depends upon the thickness of the material and the
On relatively thin
process used for joining.
materials, one- to three-sixteenths inch thickness,
the square butt joint is usually satisfactory for both
processes. For thicker metal, either a single-vee
bevel or double-vee bevel may be necessary.
Figure 10-23.—Recommended joint design for pipe.
single-vee groove or a double-vee groove, as shown
in figure 10-24. The edges of tubular sections are
prepared the same as the edges of plate of
corresponding thickness.
The welding of tubular sections employs the
same techniques as those used for plate and pipe,
with the exception that a backup is not used when
welding is to be done from both sides. In this case,
the back-chipping technique is used to ensure
high-quality welds in the finished product. Backup
plates are recommended wherever possible to
control weld penetration. These plates also permit
faster welding speeds.
Figure 10-24.—Single-vee and double-vee groove welds.
Good joint fit-up makes welding easier, saves
filler metal and shielding gas, and helps to assure
quality welds. If jigs are not used to hold the joint
members in their correct position, tack welding may
be necessary. Tack welds should be short in length,
one-fourth to one-half inch. They should also be
small in size, one-eighth to three-sixteenths inch,
depending upon the size of the metal. In addition,
tack welds should be sufficient in number and
correctly placed to maintain proper alignment of
units or components being welded. The number of
tacks to be made is determined by the workpiece to
be welded.
and a bare filler rod of suitable alloy is manually
added to the molten pool. Welding can be done
rapidly from all positions. No flux is required in
GTA welding because the action of the arc breaks
up the oxide film and allows good weld-metal flow.
A shield of gas, either argon or helium or a mixture
of argon and helium, surrounds the electrode and
the weld pool to prevent oxidation during welding.
Since the heat of the tungsten arc is
concentrated in a small area, it is much faster than
oxyacetylene welding. Distortion in GTA welds is
also appreciably less than for oxyacetylene welds.
Welding Power Source
The GTA process is widely used for welding
relatively thin aluminum sections. In this process,
an arc is established between a nonconsumable
tungsten electrode and the aluminum parts to be
welded with a shield of gas enveloping the arc and
weld pool. The arc melts the aluminum base metal,
The heat for any arc-welding process is
generated by the arc between the electrode and the
base metal. The welding current for GTA welding
is supplied by the ac/dc transformer-rectifier welder
(fig. 10-25). This machine will deliver ac
Figure 10-25.—Equipment for GTA welding.
high-frequency, dc reverse polarity (DCRP), and dc
straight polarity (DCSP) welding current. Except
for high frequency, ac welding is only authorized for
use on tenders and shore facilities. Exceptions will
require approval.
High-frequency ac is recommended for the
welding of aluminum. It offers both the advantages
of DCSP and DCRP welding. Theoretically, ac
welding can be called a combination of DCSP and
DCRP welding, as shown in figure 10-26.
In ac welding, when the current passes through
zero (fig. 10-26), the arc is broken. To restart the
arc, a high-voltage, high-frequency, low-power
additional current is used. This establishes an
ionized path for welding current to follow, when the
arc is struck at zero current.
Figure 10-26.—Ac welding as a combination of dc straight
and reverse polarity welding.
In any GTA welding operation, selection of the
proper current is of utmost importance. Table 10-6
may be used as a guide for the selection of current
for welding some of the more common metals.
Table 10-6.—Current Selection for GTA Welding
Alternating Current
Direct Current
with high frequency stabilization
Aluminum-up to 3/32 inch thich
Aluminum-over 3/32 inch thich
Aluminum castings
Brass alloys
Stainless steel
Hard surfacing alloys
Silicon copper
Key: 1. Excellent Results
2. Good Results
N.R. Not recommended
Overheating can melt the silver-brazed metal joints
in the torch and the plastic water tube that sheaths
the electric cable. A control mechanism is available
that does not allow the welding current to start
unless the water is flowing. Some GTA welding
equipment is provided with a solenoid valve that
automatically shuts off the water supply when the
welding stops. This prevents excessive cooling and
moisture condensation inside the torch. Moisture
can contaminate the electrode and cause porosity in
the weld during the initial weld period. When GTA
equipment is to be used in the field and if water is
not available, a small water tank and pump can be
used to circulate water between the tank and the
torch. The GTA welding torch carries the welding
current and directs the gas to the weld area. The
torch must be properly insulated for the maximum
current ranges to ensure operational safety.
Current is transmitted from the ac transformer
through the power cable to a collet holding the
tungsten electrode. Gas ports surrounding the
electrode permit the gas to enter the nozzle or
Welding Equipment and Supplies
In addition to the ac power source, the following
equipment is needed for GTA welding:
GTA welding torch. (Note that the word
torch is commonly used for this GTA
welding device. It is also termed electrode
holder. However, throughout this discussion
the word torch will be used.)
Gas supply, regulator-flowmeter, hose, and
Filler metal
Water supply and fittings
Helmet or eye shield, and protective
Stainless-steel wire brush
For currents above 200 amperes, cooling the
torch and power cable is necessary because of heat
generated by the arc and the current passing
through the cable. For welding currents below 200
amperes, air-cooled torches are satisfactory. A
sectional sketch of a GTA water-cooled torch is
shown in figure 10-27.
Water used to cool the welding torch should be
clean to prevent clogging or flow restriction.
The electrode should extend beyond the end of
the gas cup a distance of l/8 to 3/16 inch. Selecting
the right size electrode for each job is important to
prevent electrode damage and poor welds caused by
too high or too low a current. Excessive current will
cause tungsten particles to transfer to the weld,
while insufficient current allows the arc to wander
erratically over the end of the electrode. With
correct current the electrode will have a stable
hemispherical end. Recommended electrode sizes
Figure 10-27.—Sectional sketch of a GTA water-cooled torch.
for various ranges of welding current are shown in
table 10-7.
We will not describe in detail the advantages
and disadvantages of the various types of electrodes
made of pure tungsten, thoriated tungsten, or
tungsten-zirconium alloy. Many welders prefer pure
tungsten for GTA welding with ac. Thoriated
tungsten is preferred for automatic GTA welding
using dc straight polarity current. A note of interest
here is that tungsten electrodes are usually
color-coded on one end. A medium green indicates
that the rod is pure tungsten. A yellow color
indicates a 1 percent thoriated tungsten rod. A light
red color indicates a 2 percent thoriated tungsten
rod. A tan color indicates that the rod is zirtung
(tungsten zirconium).
The gas cup or nozzle of the torch can be either
ceramic or metal. Ceramic nozzles are generally
unsatisfactory for welding at high-current levels
because the nozzle may melt at the tip and partially
close the orifice. On the other hand, metal nozzles
of too small diameter will short out the
high-frequency current if the work is touched by the
nozzle. Torch manufacturers usually recommend
the type and size of nozzle for different current
ranges. Generally, the nozzle diameter should be
equal to or slightly greater than the molten weld
Dual Action of the AC Arc
The first function of the ac arc is to provide the
heat necessary to melt the base and filler metals.
The second arc function is to break up and remove
the surface oxides from the aluminum. This is
called the “cleaning action,” and takes place during
that part of the ac cycle when the electrode is
positive. The cleaning action is either a result of
the electrons leaving the base plate or the gas ions
striking the surface or a combination of both.
Shielding Gas
Initially the arc breaks up the oxide on the area
where it is directed. The gas shields the arc and
weld pool, preventing oxidation from reoccurring.
The gas also shields and prevents oxidation of the
hot tip of the tungsten electrode; and because of
this, the flow of gas should not be stopped until the
tungsten electrode tip has cooled. Shutoff can be
either manual or automatic; the latter is preferred.
Another function of the gas shield is to provide a
more easily ionized path, thus aiding smooth
transfer of current. Either argon or helium can be
used for shielding the arc in the GTA process.
Helium requires a higher gas flow, but gives greater
penetration and faster welding speeds than argon.
This deeper penetration is obtained because the arc
in the helium atmosphere is hotter than in the argon
atmosphere. Argon is preferred by most welders
because the cleaning action is greater and the arc
more stable. The flow of gas necessary for good
GTA welding depends on the welding current, size
of nozzle, joint design, speed of welding, and
freedom from draft in the area where the welding is
being done. This last factor can affect gas coverage
considerably. Recommended gas flows are shown in
table 10-8.
Table 10-7.—Recommended Current Ranges for Thoriated and Nonthoriated Tungsten Electrodes
Current, Amperes
Electrode Diameter Inches
Standard Tungsten Electrodes
Thoriated Tungsten Electrodes
Table 10-8.—Recommended Practices for GTA Welding of Aluminum
Dia. of
Gas Flow
No. of
Horiz & Vert.
Sq. Butt
Sq. Butt
Sq. Butt
Horiz & Vert.
Sq. Butt
Sq. Butt
Sq. Butt
Horiz & Vert.
60° Single Bevel
60° Single Bevel
100° Single Bevel
Horiz & Vert.
60° Single Bevel
60° Single Bevel
100° Single Bevel
Horiz & Vert.
60° Single Bevel
60° Single Bevel
100° Single Bevel
60° Single Bevel
Joint Design
See exercises for joint designs.
For standard (non-thoriated) tungsten electrodes.
Helium is not generally used on gas tungsten-arc welding; however, gas flow rates for it are slightly
higher than for argon.
Filler Metal
Additional filler metal is not necessary in GTA
welding when enough parent metal is provided by
the joint design to form the weld bead. For other
welds, it is often necessary to add filler metal. For
filler metal in the form of straight length, bare rod
is used for manual welding, while filler metal in wire
form, spool wound is used for automatic welding.
Filler rods of EC, 1100, 4043, 5154, 5183, 5356,
5556, and other alloys are available in various
diameters. Take care to see that a compatible filler
metal is used in welding different aluminum alloys.
Weld craters and longitudinal cracks may result
from using incorrect filler alloy. Make a special
effort to see that only clean rods are used. Dirty
rods contaminate the weld. Store rods in a hot
locker or warm dry area and keep them covered.
Now that we have covered various fundamentals
of GTA welding of aluminum, let us turn our
attention to some practical exercises that will help
you acquire skill in performing GTA welding
A thorough knowledge of the
procedures covered in the following projects will aid
you in assignments as the operator on GTA welding
Setting Up Equipment
This exercise in setting up equipment will
acquaint you with the equipment and accessories
commonly used in GTA welding. The basic
equipment and accessories required for GTA
welding of aluminum are as follows:
—Ac welding transformer with capacity range of
90 to 500 amperes having superimposed
high-frequency current
—GTA welding torch and 0.040-inch, 1/16-inch,
l/8-inch, 3/32-inch, 5/32-inch, 3/16-inch, and 1/4-inch
diameter tungsten electrodes, collets, and suitable
gas cup nozzles
—Argon gas, usually a cylinder with a
regulator-flowmeter, a solenoid control valve
interlocked with the welding circuit, or a manual
cut-off valve (called an economizer) in the gas line
before the torch
—Water supply, main shut-off valve, and
solenoid control valve interlocked with the welding
—Steel worktable and C-clamps
—Welding helmet, gloves, and protective
—Stainless-steel wire brush for cleaning oxide
from the surfaces on which weld metal will be
NOTE: Reference to standard equipment in the
following exercises will be briefly summarized, but
anticipates all previously indicated items.
Specific information on the different makes of
GTA welding equipment is not given in this training
We suggest the operator read the
manufacturer’s instruction pamphlets for specialized
Most GTA welding transformers are operated
from a 220- or 440-volt ac power source. Normally,
an Electrician’s Mate is the only one allowed to
connect or disconnect a transformer. However, you
should know the electrical hookup and be aware
that high voltages, if incorrectly handled, may cause
a fatal injury.
The high-frequency current imposed on the
welding current often affects radio reception unless
the transformer is properly installed, grounded, and
adjusted. Therefore, the manufacturer’s instructions
on these points should be carefully followed.
The power cable to the GTA welding torch, and
the ground cable to the work, should be connected
according to the manufacturer’s directions. The
welding torch should be hung in a safe location so
that the tungsten electrode cannot touch anything
grounded and thus complete an electrical circuit.
The switch controlling power to the torch should
always be in the “off” position when welding is not
being done.
The following checks should be made before
starting to weld with GTA units:
1. Be sure the torch is the right type and
capacity for the current at which most of the
welding will be done. Some manufacturers offer
different torches for different ranges of welding
2. Check the size, appearance, and position of
the tungsten electrode in the torch. It should be
clean and silvery, and the diameter should be that
recommended for the welding current to be used.
A dirty, rough electrode surface usually means that
the inert gas was shut off before the electrode
cooled, that there was air leakage in the gas supply
system or torch proper, or that the electrode tip was
contaminated by touching metal. A dirty tungsten
electrode can sometimes be cleaned satisfactorily
with a fine emery cloth. If severely contaminated,
the electrode should be replaced or the tip broken
off and dressed on a grinding wheel. (NOTE: The
dust produced from grinding thoriated electrodes is
radioactive. However, this contamination normally
does not exceed the maximum permissible
concentrations. Even though the radioactive hazard
of grinding thoriated tungsten is slight, care should
be taken to grind electrodes on specially designed
and constructed grinders.) When you are welding,
the tip should be hemispherical in shape. The
needlepoint tips used for stainless steel should not
be used for aluminum. A contaminated and a good
tungsten electrode are shown in figure 10-28. Note
the hemispherical tip on the good electrode. The
electrode should extend beyond the end of the gas
cup a distance of l/8 to 3/16 inch. It must be
securely held in the torch both for positioning and
for good electrical contact. Because small diameter
electrodes are easily bent, check to see that the
electrode is straight and centered in the cup. If
necessary, straighten or replace the electrode.
skin should never be exposed to the rays of the
welding arc because painful burns may result.
If you are teaching a person how to set up the
equipment, you should demonstrate turning on the
water and gas supply, switching on the transformer,
presetting the gas flow and current range, and then
shutting down the equipment. You should then
have the person repeat the start-up and shut-down
procedures until the procedures are thoroughly
Establishing an Arc and
Forming a Weld Pool
Figure 10-28.—Contaminated and good tungsten electrodes.
This exercise is intended to acquaint you with
the correct technique of initiating an arc and
forming the weld pool.
3. Check the connections on the gas supply for
leaks with soapy water.
4. Select the proper gas cup size according to
the torch manufacturer’s instructions. Make sure
the gas cup is free of spatter. Clean or replace it if
As material for this exercise, 1/4" by 6" by 12"
plate of any aluminum alloy recommended for
welding may be used. You will need a standard ac
transformer, GTA welding torch equipped with
5/32-inch diameter tungsten electrode, argon gas,
and necessary accessories. The procedure calls for
regulating the argon gas flow 30 to 35 cubic feet per
hour. Also, select a welding current of 175 to 225
5. Check the ground cable connections to the
The connections should also be
periodically checked after welding begins, as they
tend to work loose. This causes the welding current
to vary.
6. Preset the current range (see table 10-7) for
the joint to be welded, and switch on the
transformer, as shown in view A of figure 10-25.
7. Open the main shut-off valve on the cylinder
of gas and adjust the flow, as shown in view B of
figure 10-25. Table 10-8 lists the recommended flow
for various welding currents.
When using ac high-frequency current, the
electrode does not need to come in contact with the
workpiece to strike the arc. The high-frequency
current will jump the gap between the tungsten
electrode and the workpiece and establish the
welding current path. To strike the arc, hold the
torch in a horizontal position, as shown in figure
10-29, about 2 inches above the work surface.
8. Be sure the water supply to be used is not at
a higher pressure than that recommended by the
torch manufacturer. If satisfactory, the water
shut-off valve is usually opened fully and the flow is
controlled by the water ports in the gun.
9. Never look at a welding arc without a hand
shield or welding helmet with the proper shade of
protective glass, or your eyes will be injured. Eye
fatigue indicates a different shade of glass is
required or there is leakage around the protective
filter glass. A No. 10 glass is satisfactory for most
GTA welding at current ranges of 75 to 200
amperes. Gauntlet gloves and protective clothing
must be worn as protection from hot metal. Bare
Figure 10-29.—Torch position for the starting swing to strike
the arc.
paragraphs. When the puddle becomes bright and
fluid, move the arc to the rear of the puddle and
add the filler metal by quickly touching the rod to
the front edge of the puddle. When the puddle
becomes bright and fluid again, repeat these steps.
Figure 10-32 shows the correct procedure for adding
filler metal. This sequence is continued until the
weld joint has been completed. The width and
height of the weld bead is determined by the speed
of travel, movement of the torch, and amount of
filler metal added.
Figure 10-30.—Position of the torch at the end of the swing
when the arc strikes.
Then, with a rapid motion, swing the electrode end
of the torch down to within an eighth of an inch of
the work surface. The arc will then strike. Figure
10-30 shows the torch position at the time the arc
strikes. After the arc has been struck, hold the
torch at a 90-degree angle to the workpiece surface
and with small circular motions, as shown in figure
10-31, form a molten puddle. When the molten
puddle has been formed, hold the torch at a
75-degree angle to the work surface and move the
torch slowly and steadily along the joint at a speed
that will produce a bead of uniform width. Move
the torch slow enough to keep the puddle bright and
fluid. No oscillating or other movement of the
torch is necessary except the steady forward
When the use of a filler metal is necessary, form
the molten puddle as described in the previous
Figure 10-32.—Addition of filler metal (flat position).
Figure 10-31.—Forming a molten puddle with a GTA torch.
When using dc straight or reverse polarity
welding current, the same motion is used for striking
the arc, but the electrode must come in contact with
the workpiece to start the flow of welding current,
unless the dc welder has high frequency to give it a
self-starting arc. When the arc has been struck,
withdraw the electrode approximately one-eighth
inch from the work surface to avoid contaminating
the electrode with the molten metal. To make the
weld bead, follow the same steps as described for ac
To stop an arc, snap the electrode quickly back
to the horizontal position. This must be done
rapidly so the arc will not damage the weld surface
or the workpiece.
You will find that welding technique improves
when you learn to weld in a comfortable position.
Quality welding is dependent upon smooth, even
manipulation of the torch and filler rod. This
cannot be accomplished if you are in an awkward or
uncomfortable position.
A common mistake often made by new
operators in GTA welding is improperly feeding the
filler rod into the arc. The arc heat should be used
to form and hold the molten pool, and the filler rod
should be melted by the leading edge of the pool.
In this way, the weld metal will always be fused into
the base metal of the workpiece. By watching the
edges of the weld pool, you can learn to judge the
pool’s fluidity, buildup, and fusion into the parent
material. Incorrect torch angle, improper torch
manipulation, too high a welding current, or too low
a welding speed can cause undercutting in the base
plate along one or both edges of the weld bead.
The surface appearance and etched cross
sections of three weld beads on a flat plate are
shown in figure 10-33.
The welding current employed in each weld
determines its quality. The weld bead shown in
view A indicates that the current selected for
welding is too high; view B indicates that the
welding current used is correct; and view C indicates
that the welding current is too low.
Figure 10-33.—Comparative GTA weld beads as determined
by electrical current.
Good weld bead appearance resulting from
using two different techniques of torch-filler rod
manipulation is shown in figure 10-35. In view A, a
bead was made using a two-step technique, namely,
intermittent filler rod addition to the weld pool and
intermittent torch movement. In view B, a bead was
made by moving the torch forward in a relatively
steady motion, feeding the filler rod intermittently
as the pool required it. This latter technique gives
improved weld bead appearance needing little or no
You should practice making weld beads on a flat
plate until you are satisfied with the workmanship.
In making satisfactory beads, practice is necessary to
develop a “steady hand.” If the appearance of weld
beads made are equivalent to the ones shown in
figure 10-36, and the sample proves satisfactory by
visual examination, you should continue on to the
next exercise. Should the sample show evidence of
poor or careless workmanship with poor bead
appearance, spatter, or cracks, as indicated in figure
10-37, you must practice until you make a weld bead
that will meet visual inspection requirements.
Weld beads made with sufficient and insufficient
shielding gas are shown in figure 10-34. Insufficient
shielding gas gives an unsound weld bead having a
very poor appearance. Using too much shielding
gas is wasteful.
Figure 10-36.—Visual inspection standards for GTA welds.
course, you will need the ac transformer, argon gas,
and necessary accessories.
Figure 10-34.—Comparative GTA weld beads as determined
by shielding gas.
Flat-Position Single-Pass Butt Welds
This exercise will help you learn the technique
of making a single-pass butt weld in the flat position
on aluminum. You should use 3/16" by 6" by 12"
EC aluminum and 1/8-inch diameter 1100 alloy filler
rod, or any other recommended combination of
parent sheet-filler alloy. You will also need a 3/16
by 1" by 12" backing strap of EC aluminum or the
same sheet-filler alloy.
The procedure for welding is to bevel abutting
edges of sheet as indicated in figure 10-38. Clean
all surfaces, including the backing strap, with
solvent, and wipe dry. Brush the weld surface areas
with a stainless-steel wire brush. Inspect and clean
the filler rod if necessary. Regulate the argon gas
flow 25 cubic feet per hour, and select a welding
current of 175 to 210 amperes. Arrange the plates
The GTA welding torch should be equipped
with a l/8-inch diameter tungsten electrode. Of
Figure 10-35.—Comparative GTA weld beads with filler rod
Figure 10-37.—Unacceptable GTA welds.
cleaning materials and backing strap, if they are
The ac transformer with superimposed
high-frequency current, a GTA welding torch
equipped with 3/16-inch diameter tungsten
electrode, argon gas, and necessary accessories are
the items of equipment needed.
The procedure is to bevel the abutting edge of
plates, as shown in figure 10-38. Clean all areas,
including the backing strap, if one is used. Brush
surfaces with a stainless-steel wire brush to remove
oxide film, and between passes if contamination is
Figure 10-38.—Joint design flat-position single-pass butt
welds in aluminum sheet.
Regulate argon gas flow at 35 cubic feet per
hour, and select a welding current of 250 to 320
as shown in figure 10-38 without jigs. Position the
plate and backup strap with all units supported and
level. Then tack weld.
In welding practice, remember that good GTA
welding is dependent upon this definite
procedure-form the molten pool in the parent
sheet. Then feed the filler rod intermittently to the
leading edge of the pool as the torch is being moved
forward. DO NOT feed the filler rod into the arc.
You should practice making single-pass butt welds
until they are satisfactory. Workmanship must pass
visual inspection standards.
Horizontal-Position Multipass Fillet
and Butt Welds
This exercise will help you learn
horizontal-position welding. Use 1/2" by 6" by 12"
EC aluminum plate and 3/16-inch diameter 1100
alloy filler rod, or any recommended parent
plate-filler alloy combination. You will also need
Figure 10-39.—Jolt design and weld pass sequence
horizontal-position multipass fillet and butt welds.
Tack weld the assembly in the flat position, and
then arrange units as shown in figure 10-39. Use a
suitable jig to hold parts steady.
Rules for quality welding in the flat position
must be followed for out-of-position GTA welding.
Cleanliness, good joint fit-up, preheat, sufficient
shielding gas, and correct welding current are
important. In addition, you will find it advisable not
to use high welding current or to deposit large weld
Direct the arc so that there is no
overheating at any one area that produces sagging
or undercutting. The filler metal addition, bead
size, and sequence have to be placed so that there
is complete fusion between passes.
The welding of a fillet joint and a butt joint in
a horizontal position is shown in figure 10-40, views
Figure 10-40.—Welding a fillet and butt joint in the
horizontal position.
A and B. The correct positioning of the torch and
addition of the filler metal at the weld pool edge to
prevent undercutting when making a horizontal
position fillet weld is shown in figure 10-41.
Vertical-Position Multipass Fillet
and Butt Welds
This exercise will brief you on the technique of
vertical position welding. You will need 1/2" by 6"
by 12" EC aluminum plate and 3/16-inch diameter
1100 alloy filler rod or any other recommended
parent plate-filler rod combination. You will also
need a backing strap, if one is used.
The equipment needed is the ac transformer
with superimposed high-frequency current, a GTA
welding torch equipped with 3/16-inch diameter
tungsten electrode, argon gas, and the necessary
Figure 10-42.—Joint design and weld pass sequence
vertical-position multipass fillet and butt welds.
Butt and fillet welds in the vertical position are
made as shown in figure 10-43.
Prepare the abutting edges of plate as shown in
figure 10-22. Clean and dry the joint area
thoroughly. Brush with a stainless-steel wire brush
to remove oxide where the filler metal will be
deposited. Examine and clean the filler rod, if
Regulate the argon gas flow at 35 cubic feet per
hour, and select a welding current from 250 to 320
Position sections as shown with all units
supported. Tack weld in the most convenient
position. Holding jigs may be used. Follow the
weld pass sequence as shown in figure 10-42.
Figure 10-41.—Correct position of the welding torch and
proper addition of the tiller metal to form a weld pool.
All of the factors presented concerning
out-of-position welding also apply here. Do not use
too high a welding current or deposit too large a
weld bead. If the molten pool is too large, it will be
difficult to control. Bead size, filler metal addition,
and bead sequence should be carefully handled to
ensure complete fusion between passes. Some
welders find that a slight weave in vertical welding
will smooth out the bead. Practice your work until
it passes satisfactory visual inspection.
Overhead-Position Multipass
Fillet and Butt Welds
This exercise will acquaint you with the
technique of overhead-position welding.
Figure 10-43.—Butt and fillet welds made in the vertical
materials, gas flow, and equipment needed for this
exercise are the same as those described for
vertical-position multipass fillet and butt welds.
Bevel the edges of abutting plates as shown in
figure 10-44. Tack weld the backing strap. Clean
and dry all joint surfaces with cleaner. Wire brush
to remove joint area oxides, and also any apparent
weld contamination after each pass.
Tack weld the parts in the most convenient
position. Position the sections as shown in figure
10-44 with all units supported. Use holding jigs, if
necessary. Follow the weld pass sequence as
Overhead multipass butt and fillet welds are
shown in figure 10-45. Here, as in vertical welding,
a slight weave may or may not be used. A lower
welding current and travel speed are used as
compared to flat-position welding. Conversely, a
higher flow of shielding gas is used. Take care to
avoid sagging and poor penetration by adding too
much filler and carrying too large a pool. Let the
established pool wet out enough before adding more
filler. Most inexperienced welders find overhead
welding awkward. Therefore, try to get in as
comfortable and relaxed a position as possible when
welding. This will help with steady, even torch and
filler rod manipulation.
The new operator should practice both fillet and
butt welding in the overhead position until satisfied
with the work. If the weld passes visual inspection,
continue on to the next exercise.
Figure 10-45.—Making overhead multipass groove and fillet
Horizontal Fixed-Position
Multipass Welding
This exercise will help you acquire the technique
of welding aluminum pipe in the horizontal fixed
position, with or without backup. Use 2 1/2-inch
diameter, schedule 80 aluminum pipe; l/8-inch
diameter, 4043 alloy filler rod, or any other
recommended parent pipe alloy-filler rod
combination; a backing ring for backup; and
cleaning solution or solvent.
With the ac transformer, you will need a GTA
welding torch equipped with l/8-inch diameter
tungsten electrode, argon gas, and necessary
accessories. You also will need a jig for holding
pipe in position and a pipe and backing ring.
The procedure involves beveling pipe edges as
indicated in joint design and weld pass sequence
shown in figure 10-46. Clean, dry, and brush the
weld areas and backup ring. Insert the ring in the
proper position after the pipe sections are clamped
on the jig. Clean the filler rod, if required.
Regulate the argon gas flow at 30 cubic feet per
hour, and select a welding current of 160 amperes.
Position sections as shown in figure 10-46, with
all units supported. Tack weld in the most
convenient position. Follow the weld pass sequence
as shown.
Figure 10-44.—Joint design and weld pass sequence
overhead-position multipass fillet and butt welds.
for GMA welding is designed to initiate gas
coverage and automatically feed the aluminum
electrode into the weld area when the arc is struck.
A welding pool is formed immediately when the arc
is established. Welding progresses by moving the
welding gun along the line of the joint at a rate to
build up a bead of the desired dimensions. The
electrode and weld pool are protected from
oxidation by the shield of gas during welding. No
flux is required.
GMA Welding Equipment
Figure 10-46.—Joint design and weld pass sequence
horizontal fixed-position multipass (GTA) welding.
Most welders prefer to use a backup ring for
pipe welding when possible because it makes the
operation easier. With backup, the joint fit and
penetration control are not so critical. You should,
however, learn to make the weld without a backup
Horizontal fixed-position pipe welding is often
considered a test to qualify for welding in any
position. It includes welding in the flat, vertical, and
overhead positions. Figure 10-47 shows the
technique of torch and filler rod handling.
Numerous types and models of GMA welding
equipment are used in the Navy. They all have the
same basic requirements. Each must have a source
of DCRP welding current, a wire feed unit for
feeding the wire filler metal, a control unit that
controls the automatic feed of the wire filler metal
and shielding gas, and a welding gun for directing
the wire filler metal and shielding gas to the weld
area. Figure 10-49 shows one type of GMA welding
equipment that is used quite often for short run
welds and welds in hard-to-get-to places that are
inaccessible to larger welding guns.
The 200 dc amp rectifier welder shown in figure
10-49 was designed specifically for the GMA
welding process and is a constant potential power
source. The constant potential power source
compensates for changes in arc length, thus
providing more uniform welding.
The GMA welding process is also known as gas
consumable electrode welding (fig. 10-48). It uses
a dc (reverse polarity) and a shield of argon or
helium or a mixture of both. A small diameter
aluminum wire serves both as electrode and filler
metal and is fed automatically from the welding gun
at high speed. Commercially available equipment
The welding gun shown in figure 10-49 contains
the wire drive motor and drive roll assembly, the
control switch for control of the wire feed and gas
flow, and a replaceable l-pound spool of wire filler
Figure 10-47.—Techniques of torch and filler rod handling for tubular sections.
welding gun does not contain the spool of filler
metal. The filler metal is on a 12-inch diameter
spool that is inside the canister. The filler metal is
fed through a lo-foot long plastic guide liner to the
drive rolls in the gun and then to the weld area.
The dc rectifier welders shown in figures 10-49 and
10-50 are connected to a 440-volt ac electrical
supply source. These welders may be used with a
220-volt ac supply source by making the necessary
electrical changes according to the manufacturer’s
technical manual.
In addition to the equipment already mentioned,
the following supplies and equipment are needed for
the GMA welding of aluminum:
Gas supply, regulator-flowmeter valve, hose,
and fittings
Filler wire
Figure 10-48.—CMA welding aluminum truck bed.
metal. The welding gun is connected directly to the
dc rectifier welder. This eliminates the need for a
separate control unit and wire drive assembly. Wire
filler metal in sizes 0.030, 3/64, and l/16 inches may
be used with this gun. The weight of the gun,
including a l-pound spool of wire, is about 3
Another GMA welding unit is shown in figure
10-50. It consists of a 250-amp dc rectifier welder,
the welding gun, and a canister. This equipment
differs from that shown in figure 10-49 in that the
Helmet or eye shield, and protective
Stainless-steel wire brush
DCRP is most often used for GMA welding of
aluminum. In DCRP welding, the electrons flow
from the plate to the filler wire. This provides the
heating effect necessary on the end of the filler wire
electrode to form molten aluminum droplets. These
droplets, in turn, are transferred into the weld pool.
The GMA process deposits filler metal at higher
rates than the GTA process, making faster, more
Figure 10-50.—Heavy-duty GMA welding equipment (AIRCO
Figure 10-49.—GMA welding equipment (AIRCO products).
Helium, argon, or mixtures of the two are
suitable for GMA welding of aluminum. At any
given current, the helium shielded arc has a higher
voltage than the argon arc. A smoother, more
stable arc is obtained with argon. Pure argon is
used most widely on aluminum plate less than
three-fourths inch thick. Combinations of argon
and helium are often employed for welding heavy
plate. This combination is used particularly for
out-of-position welding to obtain the “hotter arc”
characteristics of helium with the stabilizing effects
of argon. Mixtures of 75 percent helium and 25
percent argon are commercially available. Other gas
mixtures, for example, 60 percent helium and 40
percent argon, are mixed by combining flows from
separate tanks of helium and argon. Helium
additions of over 10 percent markedly change the
arc characteristics.
economical welds with less heat effect on the
Dual Action of the Arc
The reverse polarity arc supplies heat to melt
the consumable filler wire and the workpiece. The
arc also breaks up the surface oxide on the
aluminum. This cleaning action is due to the
electrical characteristics of the DCRP arc. Arc
action is not intermittent as in ac GTA welding, but
is continuous because there is no change in current
direction using dc GMA welding.
Shielding Gas
The GMA welding gun deposits molten
aluminum where directed on the workpiece. The
gas shields the arc and weld pool while the filler
wire is being melted and transferred in spray or
droplet form to the pool. Another purpose of the
gas shield is to provide a more easily ionized path
than air.
The flow of gas necessary for good quality GMA
welding depends upon the gas used, welding current,
diameter of gun nozzle, joint design, welding
position, speed of welding, and freedom from draft
Table 10-9.—Recommended Practices for GMA Welding of Aluminum Alloys
Welding Position
Joint Degree
Wire Dia.
Argon (2)
Gas Flow
No. of
Horiz. & Vert.
Horiz. & Vert.
None or Single Bevel
Single Bevel
Single Bevel
2 or 3
2 or 3
Horiz. & Vert.
Single or Double Bevel
Single or Double Bevel
Single or Double Bevel
1 ot 2
Horiz. & Vert.
Single or Double Bevel
Single or Double Bevel
Single or Double Bevel
2 or 3
3 or 4
8 to 10
Horiz. & Vert.
Single or Double Bevel
Single or Double Bevel
Single or Double Bevel
4 to 5
4 to 6
15 or more
Single or Double Bevel
12 or more
Single or Double Bevel
20 or more
See exercises for Joint Designs.
Gas flows for helium are slightly higher than for argon. Lower flows are possible as mentioned in Part I-Basic Theory.
Preheat optional.
in the welding area. This last factor can affect gas
usage and weld quality considerably, so it is
recommended that the welding area be essentially
draft-free. When welding in the field, suitable
shielding with curtains or other type of windbreak
should be provided to prevent natural air currents
from interfering with the gas flow. Recommended
gas flows for GMA welding are shown in table 10-9.
Table 10-11.—Recommended Welding Current Ranges for
Various Diameters of GMA Filler Wire
Filler Wire Diameter
l/8 (l)
Filler Metal
Filler wire of EC, 1100, 4043, 5154, 5183, and
5356 and others are available in 0.030-, 3/64-, l/16-,
and 3/32-inch diameters. It is necessary that the
correct alloys be used for the specific welding job.
The recommended alloy of filler wire for the various
alloys is shown in table 10-10. The recommended
filler wire diameters for welding various metal
thicknesses and in different current ranges are listed
in table 10-11.
(2) Maximum welding current dependent on the
power source.
stored in a hot locker or in a warm dry area and
should be kept covered. If welding is stopped for
any length of time, remove the wire and place it
in the original carton to prevent possible
Before welding with GMA equipment, be sure
that all controls are properly adjusted, all
connections are correctly made, and all safety
precautions are being observed. Wear protective
clothing, including a helmet with a suitable filter
lens. Hold the welding gun as shown in figure
10-51. Support the weight of the welding cable and
Table 10-10.—Recommended Filler Materials for GMA
Welding of Various Aluminum Alloys
400 and up
(1) Normally used for automatic welding.
The wire that you use must be clean. Unsound
welds result from wire that has been contaminated
by oil, grease, dust, or shop fumes. Your best
welding results are obtained by using wire that has
just been taken out of its carton. Wire should be
Parent Metal Sheet,
Plate or Tube
Welding Current
Filler Alloy
(1) For high temperature applications, first
choice for filler metal is alloy 5554 otherwise,
use 5356 or 5183 for higher strength
Figure 10-51.—Positioning the GMA gun prior to welding.
gas hose across your shoulder to ensure free
movement of the welding gun. Hold the gun close
to, but not touching, the workpiece. Lower your
helmet and squeeze the trigger on the gun.
Squeezing the trigger starts the flow of shielding gas
and energizes the welding circuit. The wire-feed
motor is not energized until the wire electrode
comes in contact with the workpiece. Move the gun
toward the work, touching the wire electrode to the
work with a sidewise scratching motion as shown in
view A of figure 10-52. To prevent sticking, pull the
gun back quickly, about one-half inch, the instant
contact is made between the wire electrode and the
workpiece. The arc will strike as soon as contact is
made and the wire-feed motor will feed the wire
automatically as long as the trigger is held.
To break the arc, just release the trigger. This
breaks the welding circuit and also de-energizes the
wire-feed motor. The wire electrode may stick to
the work when you strike the arc, or at any time
during welding. If that happens, release the trigger
and clip the wire with a pair of pliers or side cutters.
A properly established arc has a soft, sizzling
sound. The arc itself is about one-fourth inch long,
or about one-half the distance between the gun
nozzle and the work. If the arc does not sound
right, adjust the wire-feed control dial or the
welding machine itself. For example, a loud,
crackling sound indicates that the arc is too short
and that the wire-feed speed is too fast. Correct
this by moving the wire-feed dial slightly
counterclockwise. This decreases wire-feed speed
and increases arc length. A clockwise movement of
the dial has the opposite effect. With experience,
you will be able to recognize the sound of the
proper length of arc.
Use the forehand technique for welding. Hold
the gun at an angle of 5° to 20° from the vertical
position, as shown in view B of figure 10-52. A
right-handed person welds from right to left. The
forehand technique provides the best coverage of
shielding gas to the weld area, and the operator has
a better view of the weld joint. A left-handed
person holds the gun in the same position relative to
the surface of the base metal, but welds from left to
You should first learn to strike and establish an
arc and to adjust the wire feed and welding current
to obtain the proper arc characteristics. Then you
should learn to run a bead. To run a practice bead,
select the proper current setting, gas flow, and
correct size filler wire as recommended in table
10-9; then, proceed as follows:
1. Hold the gun in the proper position, close to
but not touching the surface of the work, and
squeeze the trigger.
2. Lower your welding helmet and strike the
3. Hold the gun at the starting point until a
puddle forms.
4. As soon as you see a puddle, move the gun
forward steadily at a rate that permits the work and
the electrode to melt at the same time. Keep the
arc in the pool of weld metal. Do not direct it into
Figure 10-52.—GMA welding. (A) Striking the arc. (B) Gun angle.
the base metal. A thin, irregular bead will result if
you move forward too rapidly. Undercutting may
result if you move the gun forward too slowly. A
good bead is uniform in width and height. The
ripple is uniform, and there is no overlap or
undercut at the edges.
Some of you may want to move the gun along
the line of weld with a steady forward motion.
Others prefer to run a bead with a reciprocating
technique like that shown in figure 10-53. When
you use this technique, strike the arc and then
slowly move the gun forward along the line of weld
about one-half inch and then back about one-fourth
inch. Continue this one-half inch forward and
one-fourth inch backward motion along the line of
weld. If you want a wide bead, use a side weave.
Here, the gun is moved uniformly back and forth
across the line of weld while steadily moving along
the line of weld. The width of the bead determines
the amount of sidewise movement.
Although GMA welding does not require the
use of a flux, it does require that the base metal be
clean. Aluminum and aluminum alloys should be
cleaned with an approved compound, or with a
stainless-steel wire brush. Any grease should be
removed with a solvent before cleaning with a
compound. Stainless-steel wire brushes that have
picked up grease should be cleaned with a solvent
before they are used to clean aluminum for welding.
Inadequate shielding gas flow resulting from
a low cylinder pressure, from restrictions in
the gas passages of the equipment, or from
improper adjustment of the flowmeter
Excessive weaving or whipping of the
welding gun
Poor fit-up of parts
Improperly cleaned base metal, or dirty
welding wire
Nonuniform wire-feed speed
Welder fatigue is often the cause of poor weld
quality and low output. You will learn that the
quality and quantity of your work improves as you
learn to weld comfortably. Out-of-position welding
is usually more awkward than flat position;
therefore, arrange the work for flat position welding
whenever possible for economy and quality.
Satisfactory weld results also depend on good
maintenance of the GMA equipment. Maintenance
procedures are outlined in the manufacturer’s
technical manual furnished with the equipment.
Weld beads made with too low, too high, and the
correct current are shown in figure 10-54.
Once you get the feel of welding with GMA
equipment, you will probably find that the
techniques are less difficult to master than many of
the other welding procedures. However, there are
some pitfalls. Porous welds may result from the
following causes:
Notice the lack of penetration and "ropy"
appearance of the weld bead made with insufficient
welding current. Also, note the deep penetration
Low arc voltage (less than 26 volts)
Low welding current
Figure 10-54.—Weld bead characteristics determined by
welding current.
Figure 10-53.—Reciprocating technique for GMA welding.
and flat appearance of the bead made with excessive
welding current.
Weld beads made with sufficient and insufficient
shielding gas are shown in figure 10-55. Inadequate
shielding gas gives an unsound weld bead having a
dirty appearance. Using too much shielding gas is
wasteful and may cause weld turbulence and
porosity. Note the appearance and penetration of
the bead made with the proper current and gas flow.
Recommended flows of shielding gas for various
thicknesses of plate are shown in table 10-9.
If the sample weld shows evidence of poor or
careless workmanship, having spatter and cracks, or
has bead appearance as indicated in views A and B
of figure 10-54 or view B of figure 10-55, it is
unsatisfactory. Continue to practice until you can
make a weld that will pass visual inspection.
Practice making weld beads on flat plate until
satisfactory workmanship results. Practice is
necessary to develop a "steady" hand. If the
appearance of your weld beads is equivalent to the
ones shown in figure 10-56, the sample is
satisfactory to visual examination.
Figure 10-56.—Acceptable single-pass and multipass GMA
To be proficient as a welder, you must be able
to make all the various types of welds in the flat,
vertical, horizontal, and overhead positions. The
following exercises will aid you in learning the
techniques employed in making different types of
welds in all positions.
Flat-Position Single-Pass Butt Welds
This exercise will help you make a single-pass
butt weld in aluminum plate. You will need 3/8" by
6" by 12" EC aluminum plate and l/16-inch diameter
1100 alloy filler wire, or any other recommended
parent plate-filler wire alloy combination. You will
also need a backing strap 1/4" by 1 1/2" by 12", cut
from the parent plate or thinner aluminum alloy
section compatible with the workpiece. In addition,
you will need a suitable solvent or cleaner for
removing dust or grease.
Use the standard
equipment and necessary accessories. Saw or
machine bevel the abutting plate surfaces, allowing
for land. Thoroughly clean the weld surface areas,
including the backing strap. Regulate the gas flow
at 50 cubic feet per hour, and select a welding
current of 230 to 300 amperes.
Aluminum plates should be prepared and placed
as shown in figure 10-57. When so placed, there
should be a slight gap between the two aluminum
Figure 10-55.—Weld bead characteristics determined by
shielding gas.
Figure 10-57.—Joint design flat-position, single-pass butt
welds in aluminum plate.
Figure 10-60.—Joint design and weld pass sequence
flat-position multipass butt welds in aluminum plate.
Figure 10-58.—Plates tack-welded and aligned for GMA
The correct arc length is very important. Too
short an arc will cause porosity; too long an arc will
result in lack of fusion. A proper arc is between
one-eighth inch to three-eighths inch long,
depending on the current, joint, and filler wire alloy.
The correct arc length, when struck, will produce a
smooth sizzling or hissing sound.
sections to permit good root fusion in the butt weld.
Ordinarily, when using a backing strap, the gap
between the parts to be welded should be not less
than the diameter of the filler wire. Slightly more
space is preferable. After the plates are aligned and
rigidly supported, tack weld, as shown in figure
10-58, before making the single weld pass. Bring
the gun into the forehand welding position, as
shown in figure 10-51. Hold the gun 5° to 20° from
the vertical, pointing in the direction of travel.
After the arc is initiated, move the gun forward at
the proper angle and speed as shown in figure
Practice making single-pass butt welds,
according to the procedure outlined, until your
weldments can pass the usual inspection standards.
Defective tack welds or defective sections of the
main weld can be chipped out and the area
The angle of the gun is dependent upon both
the speed of travel and the position of the joint.
Adjust this angle to give the proper cleaning action,
depth of penetration, and bead contour. When
welding unequal sections, direct the arc against the
heavier piece to obtain equal fusion in the two
Flat-Position Multipass Butt Welds
This exercise will help you make multipass
flat-position GMA butt welds in aluminum plate.
The material requirements include 1/2" by 6" by 12"
EC aluminum plate and 3/32-inch diameter 1100
alloy filler wire, or any other parent plate-filler wire
alloy combination recommended for welding; a
compatible aluminum alloy backing strap, if used,
and degreasing solvent or solution.
Prepare the abutting plate edges by milling or
sawing to the proper angles, shown in figure 10-60.
Clean the weld area and backing strap, if used. Use
solvent, and wipe dry. When more than a single
pass is made, wire brush after each pass if
contamination is visible. Regulate the gas flow at 50
cubic feet per hour, and use a welding current of
280 to 320 amperes.
One method of weld pass sequence is shown in
figure 10-60. You should always watch the weld
pool. This is the only way to determine if there is
proper penetration and fusion. The fluidity of the
Figure 10-59.—Moving the welding gun forward at the
proper angle.
Figure 10-63.—Voids in multipass butt welds.
Figure 10-61.—Gross section of two welds showing poor root
fusion and too heavy a root face.
Cross sections of good multipass GMA butt
welds are shown in figure 10-64. The welds have
good root fusion and are free from weld skips,
inclusions, and porosity.
molten pool, especially near its edges, is important.
The gun angle used for making multipass butt welds
in the flat position is the same as that used in
making single-pass butt welds. It is sometimes
necessary to lower the welding current when making
later successive passes because of heat buildup.
Clean between passes with a stainless-steel wire
brush for improved welding results. Etched cross
sections of two welds, shown in figure 10-61,
illustrate poor root fusion caused by too heavy a
root face and/or inadequate joint spacing. Welding
with too low a welding current or too high a welding
speed may also cause this condition.
Practice the weld joints shown in figure 10-60
until your workmanship is satisfactory. Take care
that you do not melt or fuse the backup when
making the root pass of a joint using a steel
orcopper backup. If this does happen, the root pass
Gross porosity in a weld is clearly shown in
figure 10-62. Insufficient shielding gas, improperly
cleaned plate, or dirty filler wire will cause such
Voids in multipass butt welds are often caused
by dirty plate, dirty filler wire, or improper welding
technique. (See fig. 10-63.)
Figure 10-64.—Cross section of good multipass GMA welds
free from defects.
Figure 10-62.—Grass porosity in a multipass butt weld.
may become contaminated with steel or copper and
will be less ductile.
Regulate the gas flow at 50 cubic feet per hour, and
use a welding current of 210 to 250 amperes.
In addition, complete an extra weldment without
backup. If there is a lack of penetration, make a
seal or finishing bead along the root of the weld.
When high-quality welds are required, the fused
back side of the joint may be chipped or burred out
to sound metal, making a groove suitable for
welding. This is shown in figure 10-65.
Follow the pass sequence as indicated in figure
10-39. Make certain that sections are properly fitted
and jigged.
Horizontal-Position Multipass
Fillet and Butt Welds
This exercise will help you learn
horizontal-position GMA welding. You will need
1/2" by 6" by 12" EC aluminum plate and l/16-inch
diameter 1100 alloy filler wire, or any other
recommended parent plate-filler wire alloy
combination. You will also need a cleaning solvent
or solution.
The equipment will be the dc rectifier, GMA
welding gun, filler wire, gas, and necessary
accessories. You will also need a jig to hold the
plates in position.
All rules for quality welding in the flat position
must be followed for out-of-position GMA welding.
Cleanliness, good joint fit-up, sufficient shielding
gas, correct welding current, and so on, are
important. You should not use a high welding
current or deposit too large a weld bead. Welding
wire one-sixteenth inch in diameter is recommended
when butt welding one-half inch thick plate in the
horizontal position. This compares to 3/32-inch
diameter welding wire for the same thickness of
plate in the flat position.
Take special care to direct the arc so that you
do not overheat any one area. This may cause
sagging or undercutting. The welding speed, bead
size, and bead sequence have to be such that there
is no lack of fusion between passes. The welding of
a fillet and a butt joint in the horizontal position is
shown in figure 10-66. Practice welding these two
joints until your workmanship is satisfactory.
Prepare the abutting edges of the plate by
machining or grinding to the proper angles, shown
in figure 10-39. Clean and dry the weld areas.
Brush with a stainless-steel wire brush before the
initial weld pass is made, and also after each
successive pass if contamination is apparent.
Figure 10-65.—Chipping out the fused back side of a joint to
make a high-quality weld.
Figure 10-66.—Welding a fillet and butt joint in the
horizontal position.
Vertical-Position Multipass Fillet
and Butt Welds
This exercise will help you learn vertical-position
GMA welding. The materials and equipment
needed are the same as those described for
horizontal-position welding. The gas flow and
current range are also the same. Machine or grind
the abutting plate edges to the angles shown in
figure 10-42. Thoroughly clean and dry the weld
areas. Clean with a wire brush between passes if
contamination shows in the weld area.
Follow the weld sequence shown in figure 10-42.
Make all welds in the upward direction. Take care
to fit the parts to be welded with the root space
Fillet and butt welds made in the vertical
position are shown in figure 10-67. Note that the
welding is done upward. All factors concerning
out-of-position horizontal welding also apply here.
Do not use too high a welding current or deposit
too large a weld bead. If the molten pool is too
large, the effects of gravity will make it difficult to
control. Bead size, weld speed, and bead sequence
must be such that there is no lack of fusion between
passes. Some welders find that a slight side-to-side
weave, approximately one-eighth inch, when done
smoothly and evenly, is helpful in vertical welding.
and equipment are the same as those used for
horizontal- and vertical-position welding. However,
in overhead-position welding, the gas flow is
regulated to flow at 60 cubic feet per hour, and the
welding current is selected at 225 to 275 amperes.
Prepare edge angles of abutting plates by
machining or grinding as shown in figure 10-44.
Clean and thoroughly dry the weld areas, using
solvent to degrease the metal. Surfaces on which
weld metal will be deposited should be wire brushed
to remove aluminum oxide coating. Brush with a
stainless-steel brush after every pass if there is
contamination. Follow the weld sequence shown in
figure 10-44. Figure 10-68 shows a welder making
overhead multipass fillet and butt welds.
Here, as in vertical welding, a slight weave may
or may not be used. A lower welding current and
travel speed are used as compared to flat-position
welding. Conversely, a higher flow of shielding gas
is used. Take extreme care to avoid sagging and
poor penetration. Trying to deposit too much metal
and carrying too large a weld pool is the direct
cause of such conditions. Most inexperienced
welders find overhead welding awkward. Assume as
comfortable and relaxed a position as possible, and
Overhead-Position Multipass Fillet
and Butt Welds
This exercise will help you learn
overhead-position GMA welding. The materials
Figure 10-67.—Welding fillet and butt joints in the vertical
Figure 10-68.—Welding overhead multipass fillet and butt
Since this welding involves flat, vertical, and
overhead welding, you should be able to weld
satisfactorily in all of these positions before
attempting fixed-position welding. Determining
factors for quality welds, previously discussed, also
hold true here.
this will help you with the steady gun handling
necessary for quality welding. Practice until your
overhead welds pass visual inspection.
Horizontal Fixed-Position
Multipass Welding
This exercise will help you learn GMA welding
of aluminum pipe, with and without backup, in the
horizontal fixed position. For this exercise, use
5-inch diameter standard aluminum pipe 6061 alloy
and 1/16-inch diameter 4043 or 5356 alloy filler
wire, or any recommended parent metal-filler wire
alloy combination. You will also need a backing
Equipment requirements include a dc
generator or rectifier, a GMA welding gun, filler
wire, gas, and necessary accessories. You will also
need a jig for holding the pipe in the welding
Most welders prefer to use a backing ring for
pipe welding, when possible, because it makes
welding easier and faster. With backup, the joint
Pipe edges should be angled to the degree
indicated in figure 10-69. Insert a backup ring and
place the assembly in a holding jig; or, place two
abutting sections in the jig if a backing ring is not
used. Thoroughly clean and dry the weld area.
Wire brush the tile surface to remove the
protective oxide coating. Brush again after each
pass if contamination appears. Regulate the gas
flow at 60 cubic feet per hour, and select a welding
current of 150 to 190 amperes. Follow the weld
sequence as shown in figure 10-69.
Horizontal fixed-position welding is often
considered a test to qualify for welding in any
location. You must weld in the flat, vertical, and
overhead positions. Manipulation of the GMA gun
for welding pipe in the horizontal fixed position is
shown in the photographic sequence in figure 10-70.
Figure 10-69.—Joint design and weld pass sequence
horizontal fixed-position multipass GMA welding.
Figure 10-70.—CMA gun manipulation for welding pipe in
the horizontal fixed position.
fit-up and the control of penetration are not as
hot sand in the eyes. The doctor will give you eye
drops that will relieve unnecessary suffering.
8. Wear suitable clothing as protection from
the spatter or molten particles and to shield your
body from rays of the arc.
Safety must be observed in GTA and GMA
welding as in any other welding process. In addition
to the safety precautions listed in chapter 1 of this
manual, the following general precautions should
also be observed:
9. Do not strike an arc on a compressed gas
1. The welding area must be properly
ventilated without excessive drafts that can affect the
welding arc and shielding gas. Carbon tetrachloride
or other chlorinated hydrocarbons should NOT be
used for cleaning aluminum before welding.
Alcohol and acetone are recommended as chemical
cleaners, but surfaces cleaned with these materials
should be thoroughly dried before welding. Welding
should not be done in any area where fumes from
such solvents are present.
2. The ac transformer used for GTA welding or
the dc generator rectifier for GMA welding is
normally fed from a 220- to 440-volt circuit. These
voltages can cause severe or fatal injuries: DO NOT
work on any wiring in an energized circuit. The
deck where welding is being done must be dry.
10. Do not weld in the vicinity of inflammable
or combustible materials. Degreasing of aluminum
with alcohol or other inflammable solvents in an
improperly ventilated welding area creates a fire
11. Do not weld on containers that have held
combustible or inflammable materials without first
exercising the proper precautions.
12. Do not weld in confined spaces without
adequate ventilation or individual respiratory
equipment. Do not weld on workpieces without
wiping off the degreasing solvent.
13. Mark metal “HOT” because aluminum does
not change color when heated.
14. Do not chip or grind without safety goggles
and a suitable face shield.
3. Welding transformers or rectifiers must have
a power ground so that welders cannot get a shock
from stray current.
4. Do not lay the torch on the work or
worktable. Hang it up in a safe place so the
electrode is not touching metal that may be
15. Do not move individual cylinders unless the
valve protection cap, where provided, is in place and
16. Do not drop or abuse cylinders in any way.
17. Make certain that cylinders are well fastened
in their stations so that they will not fall.
5. Do not change a tungsten electrode before
it has cooled or while the transformer switch is in
the “on” position. Do not change spools of filler
wire while the generator or rectifier is on.
18. Do not use a hammer or wrench to open
cylinder valves.
19. Never force connections that do not fit.
6. Do not use defective welding cable. If any
of the connections are operating hot, you may have
a poor electrical connection.
20. Never tamper with cylinder safety devices.
21. Always protect hose and welding cable from
being trampled or run over. Avoid tangles and
kinks. Do not leave the hose and cable so they can
trip people.
7. Use a welding helmet when looking at the
arc. Use the correct shade of lens, usually No. 10
for GTA and No. 12 for GMA. If your eyes
become irritated, see the doctor immediately. If not
treated promptly, the irritation caused by burning
rays of the arc becomes very painful and feels like
22. Protect the hose, cable, and cylinders from
flying sparks, hot metal, hot objects, and open
25. When welding is to be stopped for an
extended l e n g t h o f t i m e , r e l e a s e t h e
pressure-adjusting screws of the regulators.
The heat necessary for coalescence is produced
by an electric arc that is drawn between the metal
stud (held in the gun) and the other workpiece part.
When the stud and the other piece have reached the
required temperature, they are brought together
under slight pressure from a spring in the gun. The
process requires relatively little skill, since many
factors are controlled automatically. When you
press the trigger of the gun, the arc is established
and controlled, the welding time is controlled, and
the stud is plunged against the plate at the proper
time and held in place until the weld is completed.
26. When welding is to be stopped for a longer
time, close the cylinder valves and then release all
gas pressure from the regulators and hose.
If you have problems getting sound welds, check
these three common errors made while stud
27. If the equipment is to be taken down, close
the cylinder valves, make certain that all gas
pressures are released from the regulators and hose,
and see that the pressure-adjusting screws are
turned in the counterclockwise direction.
Improper amperage supplied to the stud gun
from the power source. Welding of 5/8-inch
studs requires amperage settings of up to
750 amps. Most stud guns require special
power sources that can deliver such high
amperages. Most shop welding machines
cannot deliver enough amperages to
properly weld studs over l/4 inch.
23. Do not allow hose to come in contact with
oil or grease; these rot the rubber and cause a
24. Be sure the connections between the
regulators, adaptors, and cylinder valves are gas
tight. Test them with soapy water under gas
28. Use flat black paint on bulkheads and
overhead of weld areas to reduce ultraviolet light
reflected from GTA or GMA welding areas.
Improper welding time selected. Consult
owner's manual or process instruction for
proper weld time selection.
In addition to the shielded metal-arc process
and the two shielded gas processes already described
in this chapter, there are two other welding
processes that you should know about. These are
stud welding and resistance welding. Each of these
processes is summarized briefly in the following
Stud welding is a relatively simple electric
welding-arc process that is used to end-weld studs to
plate or other pieces. Stud welding was first
developed to fasten wooden decking to steel plates,
but it has become widely used for a variety of other
applications. The equipment required for stud
welding includes (1) a stud welding gun, (2) a timing
device to control the time of current flow, (3) a
source of dc power for welding, and (4) a supply of
specially designed metal studs and ferrules. A
typical portable stud welding gun is shown in figure
10-71. Figure 10-72 shows the connections between
the various units in the system.
Base metal not cleaned properly. Remove
all rust, paint, oil, or grease from weld area
and grind to bare metal.
Of all the electric welding processes discussed in
this chapter, resistance welding is the only one that
cannot be considered as an arc process. Electrodes
are used in resistance welding, but they do not
create an arc. Instead, the electrodes (there are
usually two of them) are pressed against the
workpieces. Current is applied, and the heat
necessary for coalescence is produced by the
resistance of the workpieces to the flow of a
low-voltage, high-amperage current.
Among the processes included in the resistance
welding group are spot welding, seam welding, and
projection welding. The discussion here is confined
to spot welding, since this is the only type of
resistance welding that is commonly used aboard
ship. Figure 10-73 shows a type of spot welding
Figure 10-71.—Stud welding gun.
machine that is commonly used on repair ships.
The machine serves to (1) transform the available
power supply to a suitable welding current; (2) apply
Figure 10-72.—Connection diagram for stud welding.
Figure 10-73.—Spot welding machine.
pressure to the work; (3) transmit current to the
work; and (4) control the intensity and the duration
of both current and pressure.
As may be seen in figure 10-79, the electrodes
are held in arms (often called horns). The work is
placed between the two electrodes, and the machine
is adjusted for the control of current, pressure, and
time. The electrode in the lower horn supports the
work, provides backing as pressure is applied by the
electrode in the upper horn, and completes the
welding circuit from the transformer that is located
in the machine. A foot pedal control permits the
operator to start the welding sequence while using
both hands to position the work between the
electrodes. When the foot pedal is depressed, the
upper electrode moves down into contact with and
applies pressure to the work. At the instant the foot
pedal is depressed, a preset, automatic timing device
takes over. First, the timer provides for SQUEEZE
TIME, during which pressure is built up in the
pressure system and is applied to the work. Next, at
the end of squeeze time, the timer provides WELD
TIME, which controls the duration of current flow.
Finally, the timer provides HOLD TIME, during
which pressure is maintained on the electrodes after
current flow stops. Hold time permits the weld
nugget to cool and solidify under pressure. The
weld that results depends on many factors, including
current, pressure, and timing settings; the condition
of the electrodes; and the surface condition of the
workpiece. Each kind and thickness of material
requires an individual setup. These adjustments are
based on tables of resistance welding data furnished
by the manufacturer.
The procedure for arc cutting is shown in figure
10-74. When cutting thin plate (under one-half
inch), you do not need to manipulate the electrode
except as required to maintain the arc and to
advance the arc as the cut progresses (fig. 10-74,
view A). When cutting heavier plate, manipulate
the electrode with an up-and-down motion in the
cut so as to displace the molten metal; keep the
electrode at an angle to the plate (fig. 10-74, view
B) so that the bottom of the plate is cut slightly
before the top. In general, metal-arc cutting is
better than carbon-arc cutting through heavy
Metal-arc cutting is also generally
preferred for rivet cutting and for hole piercing.
Gas tungsten-arc cutting is an arc-cutting process
used for cutting aluminum alloys. A
high-temperature, high-velocity arc is established
between the tungsten arc and the workpiece. A
shielding gas mixture of hydrogen and argon
emerges from the nozzle at a sufficiently high
velocity to blow the molten metal from the cut.
Most of the safety precautions concerning arc
welding that are given in chapter 1 of this training
manual also apply to arc cutting. Be sure that you
are entirely familiar with all appropriate safety
Arc cutting is a melting process rather than a
burning process. The heat of the arc is used to melt
the metal along the line of cut. This method does
not produce cuts of the quality produced by
oxyacetylene cutting, but it has the advantage of
being applicable to almost all metals (including
nonferrous metals).
Two arc-cutting procedures are commonly used.
CARBON-ARC CUTTING is done with a carbon
or graphite electrode. SHIELDED METAL-ARC
CUTTING is done with a covered metal electrode.
DC and straight polarity are preferred for both of
these types of arc cutting. Conventional arc welding
power sources are used for both of these types of
arc cutting.
Figure 10-74.—Techniques for arc cutting. (A) Thin plate.
(B) Heavy plate.
precautions before attempting any arc-cutting
Air carbon-arc cutting is a method of cutting or
gouging metal by melting it with the heat of an
electric arc and blowing away the molten metal with
a high-velocity jet of compressed air. The flow of
compressed air is parallel and external to the carbon
Because it does not depend upon
oxidation of the metal, air carbon-arc cutting is very
effective in cutting nonferrous metals.
The air carbon-arc gun shown in figure 10-75 is
used to clamp a carbon-graphite electrode in such a
position that air emitted from orifices in the gun
nozzle is directed parallel to the electrode. The air
then strikes the molten metal immediately behind
the arc. The gun also contains an air control valve
and the cable that carries both the current and the
air. This cable is connected to a dc welding
machine delivering reverse polarity current, and also
to a source of compressed air.
The carbon electrodes used for this cutting
process are copper coated to increase their life,
provide a uniform cut, increase their
current-carrying capacity, and reduce the radiated
heat. The carbon electrodes, used with the gun
shown in figure 10-75, may vary in diameter size
from 5/32 to 3/8 inch. The amperage settings for
these rods should be according to the
recommendations of the manufacturer, but may vary
from a minimum of 75 amps for the 5/32-inch rod
to a maximum of 800 amps with the 3/8-inch rod.
The compressed air for this process is supplied
by the ship’s low-pressure air system or by an
appropriate air compressor. Most cutting
applications require 80 to 100 psi air pressure,
although pressures as low as 40 psi can be used for
light work. On heavy work, pressures up to 125 psi
may be necessary. The air supply hoses for this
process should have a minimum inside diameter of
one-fourth inch, and there should be no restrictions
of the air flow through the hoses.
To make a cut, hold the gun with the electrode
at the desired angle of cut and strike an arc between
the end of the electrode and the metal to be cut.
The jet of compressed air is then turned on by
depressing the air valve trigger. After being
depressed, the trigger may be turned a quarter turn
in either direction for continuous flow of air. The
air jets are directed immediately behind the point of
arcing, and the electrode is moved forward as the
molten metal is blown away by the air jets. Speed
of travel is determined by the electrode size, type of
metal being cut, amperage setting, and air pressure
used. Proper speed of travel produces a good clean
cut and is recognized by a smooth hissing sound.
Air carbon-arc cutting offers certain advantages
over oxyacetylene cutting. The heat penetration is
shallower with this process, and the volume of metal
adjacent to the cut which is subjected to a high rise
in temperature during cutting is also less. As a
result, there is less warpage and distortion of the
metal being cut.
In all cutting operations, be careful that hot slag
does not come in contact with any combustible
material. Globules of hot slag can roll along a deck
for quite a distance. Do not cut within 30 or 40 feet
of unprotected combustible materials. If
combustible materials cannot be removed, cover
them with sheet metal or another noncombustible
Many of the safety precautions discussed in
chapter 1 of this training manual apply to cutting as
well as to welding. Be sure that you are entirely
familiar with all appropriate safety precautions
before attempting any cutting operation.
Figure 10-75.—Air carbon-arc gun.
You have been introduced to welding
equipment, its use, and the safety precautions
associated with the equipment. Various processes
and techniques were also discussed to give you an
insight to welding and arc-cutting operations.
However, knowing both the equipment and the safe
operation of this equipment is only the first step.
Your ultimate goal is to put your knowledge to use.
Upon completion of this chapter; you will be able to do the following:
Describe the various types of nondestructive tests (NDTs) performed on
welded or brazed joints.
Discuss some of the equipment used to perform NDTs
Describe the various nondestructive testing symbols used.
Discuss the procedures for hydrostatic and operational tests of ships’
systems and piping systems.
Official (acceptance) tests must be performed by
personnel with current certification by the Naval Sea
A component is only as good as its weld. If the weld
is not sound and is subject to cracking under normal
wear and use, then the material that has been welded is
of no use. Nondestructive tests (NDT) ensure that the
welds, castings, forging, and components are of good
quality. This chapter will discuss the various NDT
methods used.
Systems Command. These include radiography, liquid
penetrant, ultrasonic, and magnetic particle tests. If you
are not certified, you may still take part in radiographic
tests (RTs) made under the direct supervision of a
qualified radiographer if you have had formal training
in the Radiological Affairs Support Manual, NAVSEA
SO420-AA-RAD-010 (RAD-10), rules and regulations.
Under these conditions, you may help prepare an item
for testing and assist with radiographic exposures
according to RAD-10 radiation protection rules.
When tests are specified, the specifications or
standards will outline in detail (1) which part is to be
inspected, (2) the testing procedure that must be used,
(3) the extent of the part that will be inspected, (4) the
qualifications of the persons making the test, (5) the
qualifications of the persons evaluating the results of
the test, (6) the acceptance levels that the test must show,
and (7) the materials and equipment to be used.
In the following pages, we will discuss the use of
radiography and ultrasonic testing (UT) and some of the
limitations of each. We will also provide some
information on the uses and limitations of magnetic
particle (MT) and liquid penetrant (PT) inspections.
The last section of this chapter discusses hydrostatic
testing of components.
Unspecified tests (tests not in the standards) may be
made, but they cannot be considered as final acceptance
tests unless they are specifically approved by the Naval
Sea Systems Command. Welders are not permitted to
inspect their own welds for final acceptance.
Before you begin any NDT of welds, you should
make a visual inspection (VT) to detect undercutting,
weld, spatter, arc strikes, cracks, and other obvious
surface defects.
There is no standardized waiver of any specified
test regardless of the type of organization making or
repairing the item. This should be understood by all
Power Supply
The power supply and cooling unit shown in view
A converts 220-volt or 440-volt, three-phase, 60-cycle
To determine the quality of a weld, we must
examine the interior of a weld for defects. To detect
internal defects, the Navy relies heavily on an
inspection method known as radiography. In this
method, a beam of radiant energy is passed through the
metal and recorded on a radiographic film, which is
similar to photographic film. The source of the energy
is an X-ray tube of radioactive isotope (Iridium-192).
X-ray machines that are practical for use on ships are
generally of medium power; that is, they can penetrate
metal that is about 3 inches thick. The source used must
be according to the guidelines of MIL-STD-271,
Requirements for Nondestructive Testing Methods.
The action of the penetrating radiation, or “beam,”
works almost exactly as a beam of sunlight or electric
light through air. But instead of being stopped or
reflected, as light is by metal or solids, it penetrates the
solid and travels through it. Some of the radiation is
scattered or absorbed by the solid, and does not get
through. A thin section of metal will “pass” more
radiation than a thick section. A radiographic film is
placed on the side of the metal opposite the source. The
image on the film (after development) will show black
where more radiation passed through and will show
lighter shades or clear white where less radiation, or no
radiation, passed through. A hole or other defect in the
metal, of even a few thousandths of an inch, will allow
more radiation to pass through than passes through the
solid metal. The film will show a shadow that is darker
at the defect and lighter AROUND the defect.
Radiography is used where the full thickness of a
part must be inspected, or seen. For best results, use
only enough energy to get the picture on the film. The
exposure time is figured from factors such as the type
of energy, type and thickness of material, film type,
screens, distance, and required image density. A thick
piece of metal will need a longer exposure time than a
thin piece.
The X-ray equipment used for radiography on some
repair ships, tenders, and at shore stations is the
275-kilovolt-peak (LVP), 10-milliamperage (mA)
portable X-ray machine. Figure 11-1 shows that the
machine consists of three principal units plus electrical
cable and water hose.
Figure 11-1.—Portable X-ray unit for a radiographic
inspection of metals.
production of X rays by the X-ray tube located in the
head. The unit also contains a heat exchanger and
blower for removing heat from the transformer and
X-ray tube parts. The head is charged with an insulating
gas (sulfur hexafluoride) to prevent electrical leakage.
The tube that actually produces the X rays is a vacuum
tube containing a negative and a positive terminal. The
negative terminal is a filament that provides a source of
electrons. The positive terminal is a target at which the
stream of electrons is focused. A high voltage applied
to the tube drives electrons from the cathode, or
negative terminal, to the anode, or positive terminal.
The higher the voltage, the greater the speed of the
electrons; resulting in a higher range of radiation.
current from the power source to 2,000-cycle,
single-phase current. It also circulates a coolant
through the X-ray tube head (views B and C) by means
of a radiator, water pump, and interconnecting hose.
Master Control
The master control (fig. 11-1, view A), when
properly set up with the power supply and tube head
(fig. 11-2), provides the means for energizing and
adjusting the kilovoltage and milliamperage of the tube
head. A timer automatically indicates the elapsed
exposure time, and de-energizes the tube at the
completion of the exposure. Indicating instruments
show the kilovoltage and milliamperage of the X-ray
beam emerging from the X-ray tube window.
The principle of X-ray generation is illustrated in
figure 11-3. Heat and X rays are generated when
rapidly moving, negatively charged particles
A transformer within the head assembly converts
low voltage to the kilovoltage required for the
Figure 11-2.—Connections for portable X-ray machine.
Figure 11-3.—Principle of X-ray generation.
(electrons) collide with a mass of matter. The
collision transforms the energy of motion (kinetic
energy) of the electron into radiant energy. The faster
the particles are moving, the shorter the wavelength
of the X rays. The greater the current (milliamperes),
the greater the intensity of the radiant energy
produced. Most of the kinetic energy is transformed
into heat. Only a small portion is transformed into
electromagnetic waves (X rays) with the ability to
travel in straight lines without displacing the matter
through which they pass.
Figure 11-2 shows how the several units of the
portable X-ray equipment are interconnected. You
can find a complete description of this setup, as well
as the details for the operation and care of the
equipment, in the handbook furnished with the
machine. This equipment should be operated only by
qualified personnel who have had the required special
training on this equipment.
Figure 11-4.—Shematic diagram for making a radiograph.
increasing the effects of the X rays on the film. These
screens perform two functions. First, they absorb long
rays from the X-ray tube and the scattered rays from the
object being radiographed and from the surrounding
area. Second, the primary X rays striking the screens
cause the screens to emit secondary rays that react on
the film in the same manner as do the primary rays. This
intensifies the amount of radiation striking the film.
The film and screens are packaged in a lightproof device
known as a cassette, which is positioned snugly against
the specimen that is to be radiographed.
The diagram in figure 11-4 illustrates the
fundamentals of radiographic exposure and the
setup of the film, specimen, and radiation source.
Note that the film assembly is placed as close as
possible to the test specimen, while the X-ray
source is some distance away. A definite space
ratio must be maintained between the specimen
and the X-ray source if a satisfactory radiograph is
to be obtained.
Other Factors
Many factors govern the results obtained in
radiography. The principal factors are the kind and
thickness of the test specimen, the type of film used,
the focal distance between the specimen and the
radiation source, the voltage applied, the exposure
Almost all industrial radiographs are made with
lead intensifying screens. Normally, lead intensifying
screens decrease the exposure time required by
time, and the location, size, and orientation of the defect.
Each of these factors has a bearing on the radiograph
Radioactive sources disintegrate with a time scale
rate expressed in terms of half-life. This may be days
for Iridium-192. Any source aboard ship must be
considered as "live" or potentially dangerous to
health, because the source cannot be turned on and off
as can an X-ray machine. NO person is to use
(expose) radioactive sources unless the use and users
are licensed by NAVSEA.
X rays and gamma rays are potentially very
dangerous to health. Therefore, the operator must be
thoroughly familiar with and use all prescribed safety
precautions when using radiation-producing
equipment. When operating radiographic equipment,
all personnel, including the operator, must be at a safe
distance from the source of radiation. A heavy
bulkhead or lead shielding is usually provided between
the radiation source and the operating personnel. The
first step before you begin the operation is to clear all
personnel from the area in which the radiograph is to be
made. The area must then be roped off. Remember that
secondary radiation scattered from the test piece or
nearby and overhead objects is potentially as dangerous
as the direct radiation from the beam itself.
Figure 11-5.—Diagram illustrating inverse square law.
be slight. The intensity at any given distance, however,
depends upon the intensity of the radiation source.
An important factor in minimizing exposure to
radiation is to reduce the amount of time material is
exposed to X rays. It stands to reason that if the
exposure time is reduced, the amount of radiation will
also be reduced. Mathematical calculations are used to
determine the amount of exposure required for different
types and thicknesses of metals.
The best radiation safety precaution is distance
between personnel and the radiation source. This is
true because the intensity of radiation varies inversely
with the square of the distance from the radiation
source. X rays, like a beam of light, cover an
increasingly larger area with lessened intensity as
they travel from the source. This principle, known as
the inverse square law, is illustrated in figure 11-5.
When the distance (D) from the radiating source is
doubled (2D), the area covered by the beam (Cl) is
quadrupled (C2). At the same time, though, the
intensity per unit of area is only one-quarter of the
value at the original distance. Thus, with sufficient
distance, the area covered by the beam may be
tremendously large, but its intensity per unit area will
Shielding also reduces radiation exposure. If a
shield is placed between the operator and the source of
radiation, the amount of radiation received by the
operator will be reduced. The denser the shielding
material, the better the protection provided. Lead is the
best shielding material available due to its dense
should have enough intensity to allow you to view film
that ranges in density from gray to black. The light
intensity source should have a variable control, a
cooling fan, and masking facilities. All radiographs are
required to be within given density ranges. A
densitometer is used to measure the density ranges of a
film to ensure compliance with the requirements.
structure. Steel bulkheads, decks, overheads, and
machinery also provide good shielding provided that
they form a solid partition between the source and the
Some of the limitations of the use of radiography
are pointed out in the information that follows. The
greatest limitation is the shortage of qualified film
interpreters. The accessibility of the item to be
radiographed is an important limitation. Accessibility
controls the placement of both the radiation source and
the film, which, in turn, controls the amount of
distortion involved. The distortion factor will be
discussed later with the interpretation of radiographs.
Shadow Formation
Remember, a radiograph is a shadow picture. Like
any shadow cast by an object in a visible light source,
the radiograph of a specimen containing a defect is
subject to distortion. The shadow cast by your body
depends on the relative position of your body to both
the light source and the surface upon which the shadow
is cast. In the same way, the different positions of the
source of radiant energy, the defect, and the film
determine the extent to which the shadow cast by the
defect is distorted.
Other limitations are the thickness and type of
material being radiographed. A 300 kVP X-ray
machine that can penetrate 3 inches of steel in a
reasonable length of time can only penetrate
approximately 2 inches of various copper-base alloys
using the same kVP rating. The thickness range for
steel, using Iridium-192 is 1/4 inch to 2 1/2 inches. The
thickness range for copper-base alloys is approximately
the same as steel.
The principles of shadow formation are shown in
figure 11-6. Note that enlargement and distortion arise
in several different ways. First, view A shows that
enlargement occurs unless the surface upon which the
shadow is cast is flush with the object itself. The greater
the distance between the object and the surface upon
which the shadow is cast, the greater the enlargement.
Second, views E and F show that if the angle of the
radiating beam or the surface upon which the shadow is
cast is other than at a right angle (90”) to the object or
film, the shadow is distorted as well as enlarged. A third
kind of distortion occurs when the radiating source is
not an ideal point source, as shown in views A, E, and
F, but radiates from a beam area containing innumerable
points, as shown in B, C, and D. As a consequence, a
halo effect results, as shown in B, C, and D, which adds
to the distortion stemming from other causes. You can
minimize this halo effect by keeping the proper focal
distance between the test specimen, the radiating
source, and the surface upon which the shadow is cast.
The interpretation of radiographs is guided by
radiographic standards set by the Naval Sea Systems
Command and published in MIL-STD-2035,
Nondestructive Testing Acceptance Criteria. Copies of
these standards are available aboard each ship or station
that have radiographic equipment. A decision on
whether or not a part is acceptable is based on a
comparison of the radiograph of the part with the
appropriate radiographic standards. The standards
provide specific guidance on the size, number, and
dispersion of various defects, and on what decisions for
either acceptance or rejection should be made by a
qualified radiographic inspector.
Keep the principles of shadow formation in mind.
Remember that the size of the shadow cast by any defect
other than a spherical defect is influenced by the way
the beam is aimed at the defect. For example, if the
defect is cylindrical and the beam is parallel to the long
axis of the cylinder, the shadow cast is that of a circle.
On the other hand, if the beam is parallel to the diameter
of the cylindrical defect, the shadow has a rectangular
shape. In other instances, what appears to be a hairline
crack may in reality be a cold shut. It is sometimes
possible to overcome this difficulty by radiographing
the specimen twice, with the direction of the radiating
You must be familiar with what is and what is not
acceptable, and with the design of the part. Unless all
sections of the metal radiographed are of uniform
thickness, a radiograph of a perfectly sound section of
metal will vary in density. Thin sections and cored
internal cavities appear as darker areas on the
radiograph. Density differences caused by the design
must not be confused with density differences caused
by defects. Film should be viewed only in an enclosure
where all background light is prevented from causing
reflections on the film. The light source for viewing
Figure 11-6.—Principles of shadow formation.
sources varied 90° from each other. Unfortunately,
many parts do not lend themselves to this procedure.
are less dense than the surrounding steel. Therefore,
they absorb a smaller portion of the beam passing
through the metal, and they show up on the radiograph
as darkened areas. The characteristics of the more
common defects revealed by a radiograph are briefly
described as follows:
The defects most frequently detected in steel welds
through the use of radiography are slag inclusion,
porosity, cracks, and incomplete fusion. Sand
inclusions, porosity, shrinkages, and hot tears are some
of the defects revealed in steel castings. These defects
Surface roughness appears as irregular light
and dark areas having contours identical to the
combined surfaces.
piece is magnetized, finely divided iron powder is
applied to it. As long as the magnetic field is not
disturbed, the iron particles will form a regular pattern
on the surface of the test piece. If the magnetic field is
disturbed by a crack or some other defect in the metal,
the pattern is interrupted and the particles cluster around
the defect.
Gas cavities are indicated by round dark areas.
Inclusions may appear as regular or irregular
light or dark areas, depending on the density of
the included material.
Shrink porosity is indicated by a lacy,
honeycombed, discontinuous pattern, while
individual shrink cavities appear as localized
dark spots, usually with a branching, or
tree-like, pattern.
The test piece may be magnetized either by passing
an electric current through it, as shown in view A of
figure 11-7, or by passing an electric current through a
coil of wire that surrounds the test piece, as shown in
view B of figure 11-8. When an electric current flows
in a straight line from one contact point to the other,
magnetic lines of force are in a circular direction, as
shown in view A of figure 11-7. When the current flow
is through a coil around the test piece, the magnetic lines
of force are longitudinal through the test piece. In order
for a defect to show up as a disturbance in the pattern
of the iron particles, the direction of the magnetic field
must be close to a right angle to the major axis of the
defect. Since the orientation of the defect is unknown,
a minimum of two current directions must be used
during the test. In figure 11-7, circular magnetism is
induced in the test piece so that the piece may be
inspected for lengthwise cracks. Longitudinal
magnetism (fig. 11-8) is induced so that the piece may
be inspected for transverse cracks. In general, magnetic
particle inspection is satisfactory for detecting surface
cracks and subsurface cracks that are not more than 1/4
inch below the surface.
Cold shuts appear as dark lines or bands that
tend to be curved. When two streams of molten
metal that are significantly different in
temperature meet and do not fuse together, the
flow is known as a cold shut.
Cracks are shown as dark lines of various
widths, while hot tears are seen as dark lines
containing many branches.
Standard radiographic plates are valuable guides in
determining the acceptability of a weld. However, the
individual who views the plates must depend a great
deal on training and experience. Further, the individual
must be sure that the radiograph plate was properly
exposed and developed. If it is not, a radiograph
showing characteristic defects may, in fact, be sound.
If there is doubt, the part should be rejected or submitted
for further radiographic inspection.
Frequently, an unacceptable weld can be salvaged
by chipping or grinding out the defects and rewelding.
When this is done, the area must be re-radiographed to
determine the acceptability of the repaired area. Before
you start to grind or chip, though, be sure that the defects
are real to avoid grinding into or through a perfectly
good section.
The type of MT inspection unit most commonly
used in the Navy is the portable unit shown in view B
of figures 11-7 and 11-8 It is a high-amperage,
low-voltage unit having a maximum magnetizing
current output of 1,000 amperes, either alternating or
direct current. It is ready to operate when it is plugged
into the voltage supply specified by the manufacturer.
The unit consists of magnetizing current source,
controls, indicating meters, three 10-foot lengths of
flexible cable for carrying the current to the test piece,
and a prod kit. The prod kit includes an insulated prod
grip fitted with an ON-OFF relay or current control
switch, a pair of heavy copper contact prods, and two
5-foot lengths of flexible cable. Cable fittings are
designed so that either end of any cable may be fitted to
the unit, to the prods, or to any other cable. The unit has
In addition to the use of radiographs to determine
acceptability, an analysis of radiographs can lead to a
correction of the conditions leading to the defects. By
comparing the results of the inspection procedures with
your knowledge of the causes of defects, you can
improve the overall quality of the product and rejects
can be reduced or eliminated.
Magnetic particle (MT) inspection can be used
for the detection of weld defects in metals or alloys
in which magnetism can be induced. While the test
Figure 11-7.—Circular magnetization—prod method.
Figure 11-8.—Longitudinal magnetization—coil method.
three outlets on the front, which makes it easy to change
from alternating to direct current or vice versa. The
outlet on the left is labeled ac, the center is COMMON,
and the right is dc. One cable will always be plugged
into the COMMON outlet. The other cable is plugged
into the ac or dc outlet, depending upon what type of
current the test requires. For most work, alternating
current magnetization will locate fatigue cracks and
similar defects extending through to the surface. Direct
current is used when a more sensitive inspection is
required to locate defects that are below the surface.
View B of figure 11-8 shows a flexible cable
wrapped around the work. This forms a coil
which, with the passage of current, induces
longitudinal magnetism in the part of the
workpiece that is surrounded by the coiled
Either of these two methods may be used, but the
prod method is probably the easiest to apply. It will
detect surface defects in most instances. With the prods,
however, only a relatively small area of the test piece
can be magnetized at any one time. This magnetized
area is limited to the distance between prod contact
points and to a few inches on each side of the current
path. To check the entire surface, it is necessary to
successively test adjacent areas by changing the
location of the prod contact points after a given area has
been tested. Each area of the test piece must be
inspected twice; once with the current passing through
the metal in one direction and again with the current
The unit can be used to produce alternating or direct
current in either of two ways:
View B of figure 11-7 shows prods attached to
the flexible cable and used as contacts through
which current is passed into and out of a portion
of the test piece. This sets up a circular
magnetization in a local area between the prod
contact points.
do not determine the seriousness of the indication, they
do serve to identify the kind of defect indicated.
passing through the metal in a direction at right angles
to the direction of the first test. One of the advantages
of the prod method is that the current can be easily
passed through the metal in any direction. Therefore,
if you think a given area is defective, you can conduct
magnetic field tests in various directions to locate the
A crack is indicated by a sharp, well-defined pattern
of magnetic particles with a definite buildup. This
indication is produced by a relatively low magnetizing
current. Seams are revealed by a straight, sharp, fine
indication. The buildup of particles is relatively weak,
and the magnetizing current must be higher than that
required to detect cracks. Small porosity and rounded
indications or similar defects are difficult to detect if
you are inexperienced. A high magnetizing current
continuously applied is usually required. The particle
patterns for these defects are fuzzy in outline and have
a medium buildup.
The prod method is used by adjusting the unit for a
current output suitable for the magnetizing and testing
to be performed for any particular kind of metal. The
amperage setting will depend on the distance between
prod contact points. The prod kit supplied with the unit
has a space between prod contact points of 4 to 6 inches.
For this space and a material thickness of less than 3/4
inch, a current setting between 300 and 400 amperes is
satisfactory. When the material thickness is 3/4 inch
and over, use 400 to 600 amperes. You can get the same
magnetic field force with less amperage if the prod
contact points are closer together. When you hold the
prods constantly at the same spacing, you can use a
greater amperage to induce a field of greater strength.
Defect Repair
Whether or not an indicated defect is to be chipped
or ground out and repaired by welding depends on the
specifications governing the job. Surface cracks are
always removed and repaired. Indications of
subsurface defects are evaluated by the inspector. If the
indication is positive, it is usually best to grind or chip
down to the solid metal and make the repair. Unless you
have had considerable experience and can differentiate
accurately between true and false indications, it is best
to use the magnetic particle inspection only to locate
surface defects. The magnetic particle inspection is
almost foolproof for this purpose. After the defects
have been repaired, the areas should be reinspected to
ensure that the repair is sound.
After adjusting the unit, place the prods in position.
Hold them in firm contact with the metal and turn on
the current. Then apply magnetic particles to the test
area with the duster bulb and observe any indicator
patterns. With the current still on, remove the excess
particles from the test area with a blower bulb and
complete the inspection. Do not move the prods until
after the current has been turned off; otherwise the
current will arc, and you would have a flash similar to
that occurring in arc welding.
The final step is to demagnetize the workpiece.
This is especially important when the workpiece is
made of high-carbon steel. Demagnetization is
essential when direct current has been used to induce
the magnetic field. It is not as necessary when
alternating current has been employed in the test. In
fact, the usual demagnetization procedure involves
placing the workpiece in an ac coil or solenoid and
slowly withdrawing it while the current passes through
the coil.
MT inspection will help you locate hairline cracks
that are otherwise invisible. The particles form an
unmistakable outline of the defect. Large voids beneath
the surface are more easily detected than small voids,
but then, any defect below the surface is more difficult
to detect than one that extends through to the surface.
Since false indications occur frequently, you must be
able to accurately interpret the particle indications to
make correct repairs to the weld.
Defect Identification
Some of the factors that help you to interpret the
test results include the amount of magnetizing current
applied, the shape of the indication, the sharpness of the
outline, the width of the pattern, and the height or
buildup of the particles. Although these characteristics
Demagnetization can be done with the portable unit
if a special demagnetizer is not available. To
demagnetize with the portable unit, form a coil of
flexible cable around the workpiece. Be sure that the
cable is plugged into the unit for the delivery of
alternating current. Set the current regulator to deliver
a current identical to that used for the inspection, and
turn on the unit. Then gradually decrease the amperage
Surface Cleaning
until the ammeter indicates zero. If the piece is large, it
may be necessary to demagnetize a small portion of the
work at a time.
After surface preparation, you should clean the
surface of the material, including areas adjacent to the
inspection area, very carefully. You can clean the
surface by swabbing it with a clean, lint-free cloth
saturated in a solvent, such as acetone or isopropyl
alcohol, or by dipping the entire piece into a solvent.
After you have cleaned the surface, remove all traces of
the cleaning materials. It is extremely important that all
dirt, grease, scale, lint, salt, and other materials are
removed. Make sure that the surface is completely dry
before the liquid penetrant is used.
You can use a small compass to check for the
presence of a magnetic field. When the compass is held
near the workpiece, deviation of the needle from its
normal position indicates the presence of a magnetic
field. If a magnetic field is present, the workpiece will
require demagnetization.
Liquid penetrant (PT) inspection is used to inspect
metals for surface defects similar to those revealed by
the MT inspection. Unlike the MT inspection, which
can reveal subsurface defects, the PT inspection reveals
only those defects that are open to the surface. Both
ferrous and nonferrous metals can be inspected by the
use of the PT inspection.
You must maintain the temperature of the liquid
penetrant and the workpiece between 50° and a
maximum of 150°. Do NOT attempt to use liquid
penetrant when this temperature cannot be maintained.
Do NOT use an open flame to increase the temperature,
since liquid penetrant materials are flammable.
Seven groups of penetrant are listed in
MIL-STD-271. According to MIL-STD-271, group 1
penetrant material should be used for all welds. The use
of a group other than group 1 penetrant material for
welds requires approval of the authorized representative
of NAVSEA. The application of all PT inspections
must be according to the appropriate MIL-STD or
NAVSEA document. Instructions prescribed for each
penetrant should be followed carefully according to the
applicable procedure, since there are some differences
in the procedures and safety precautions required for
various penetrants.
When the material is clean and dry, coat the surface
with the liquid penetrant. The penetrant may be sprayed
on, brushed on, or the entire piece may be immersed in
the penetrant. You must allow time for the penetrant to
get into all cracks, crevices, or other defects that are
open to the surface. Wet the surface of the piece with
the penetrant and keep it wet for a minimum of 15 to 20
minutes. The time limits will vary depending upon
which group of penetrant is being used. Follow the
instructions prescribed by the appropriate MIL-STD or
NAVSEA document concerning the length of time the
surface must be kept wet.
When the surface has been kept wet with the
penetrant for the required length of time, remove the
excess penetrant from the surface with a clean, dry,
lint-free cloth or absorbent paper towel. Then, dampen
a clean, lint-free cloth or absorbent paper towel with
penetrant remover and wipe the remaining excess
penetrant from the test surface. Dry the test surfaces
after removal of excess penetrant only by normal
evaporation, or with the clean, lint-free cloth or
absorbent paper towel previously mentioned. When
you are drying the surface, be very careful so that you
do not contaminate the surface with any oil, lint, dust,
or other materials that would interfere with the
The following procedures should be followed when
you use liquid penetrants to inspect a weld.
Surface Preparation
First, you must prepare the surface. Remove all
slag from the surface. Except where a specific finish is
required, it is not necessary to grind the weld surface as
long as the weld surface is in accordance with applicable
specifications and as long as the weld contour blends
into the base metal without undercutting. If a specific
finish is required, PT inspections may be made before
the finish is made. This will detect defects that extend
beyond the final dimensions, but a final liquid penetrant
must he made AFTER the specified finish is made.
After the surface has been dried, you must apply
another substance called a “developer.” The developer
(powder or liquid) must be allowed to stay on the
actually present, or whether the indications are merely
caused by excess penetrant. If the second PT inspection
does not reveal indications in the same locations, it is
usually safe to assume that the first indications were not
really indications of defects.
surface for a minimum of 7 minutes before the
inspection is started. It can be left on no longer than 30
minutes; this leaves a total of 23 minutes to evaluate the
Let’s stop for a moment and examine what takes
place when these penetrant materials are applied. First
of all, the penetrant applied to the surface of the material
will seep into any passageway open to the surface, as
shown in view A of figure 11-9. The penetrant is
normally red in color and, like penetrating oil, it seeps
into any cracks or crevices that are open to the surface.
Next, the excess penetrant is removed from the surface
of the metal with the penetrant remover and a lint-free
absorbent material. Only the penetrant on top of the
metal surface is removed (view B, fig. 11-9); thus, only
the penetrant that has seeped into the defect is left.
All penetrant inspection materials must be removed
as soon as possible after the final inspection has been
made. Use water or solvents, as appropriate.
You must observe a number of safety precautions
while working with liquid penetrant materials. Since
the materials are flammable, they must not be used near
open flames, and they must not be applied to any surface
that is at a temperature higher than 150°F. Many of the
solvents are also poisonous in the vapor form and highly
irritating to the skin in the liquid form. Handle all
penetrant inspection materials with respect for their
hazardous nature.
Finally, the white developer is applied to the surface
of the metal. (See view C, fig. 11-9.) The developer,
an absorbing material, will actually draw the penetrant
from the defect. Therefore, the red penetrant
indications in the white developer represent the
defective area. The amount of red penetrant drawn
from the defective area will give an indication of the
size and sometimes the type of defect.
In addition to radiography, ultrasonic tests (UT) are
also used to inspect the interior of metal and welds.
Defects lying throughout the thickness or depth of a
weld are easily detected.
Defect Interpretation
When liquid penetrants are used, the lighting in the
test area must be bright enough so that you can see any
indications of defects shown on the test surface. These
indications must be carefully interpreted and evaluated.
There are normally some insignificant indications in all
inspections. Most of them are caused by failure to
remove all excess penetrant from the surface. At least
10 percent of the areas that are questionable on the
accuracy of the indications should have the penetrant
and the developer removed from the surface. Then the
area must be retested to determine whether defects are
Several techniques for the ultrasonic testing of
metals have been developed within the past few years
and are now widely used in the Navy.
Some of the defects detectable by ultrasonic
inspection are cracks, lack of fusion, slag inclusions,
porosity, lamination, and incomplete penetration. The
following section gives only basic information on the
principle of ultrasonic weld inspection. More
information can be found in MIL-STD-271.
Figure 11-9.—Principles of liquid penetrant inspection.
The term ultrasonic means vibrations or sound
waves whose frequencies are greater than those that
affect the human ear (greater than about 20,000 cycles
per second). The Navy uses equipment that has, for
practical purposes, a frequency range between 500,000
and 10,000,000 cycles per second.
where it is converted back to electrical energy. It is then
relayed to an amplifier. The beam is then presented on
a cathode ray tube (CRT) screen as vertical deflections
of the base line. Figure 11-11 is a block diagram
showing this principle.
CRT SCREEN.—The CRT screen shows a base
line of light along the lower part of the screen. The
initial pulse bounce between the transducer and the
metal is shown as a peak rising from this line at the left
or start position. It takes a certain amount of time for a
signal or beam to travel through the metal, and
approximately the same amount of time to bounce back.
This time is calibrated along the base line as distance,
or as the distance traveled by the beam front in a certain
time. If a test piece has a certain thickness and no
defects, the CRT screen will show the start position peak
somewhere on the left of the base line and another peak
(back reflection) to the right of the base line at a distance
proportional to the thickness of the piece. The
relationship of the actual thickness of the test piece to
the distance shown on the base line may be determined
from the calibration settings on the instrument. These
two peaks will be relatively high on the screen and will
represent the beam entrance into the piece and reflection
from the opposite surface, respectively. If there were a
defect between the two surfaces, SOME of the beam
would BOUNCE from the boundaries of the defect and
would show on the CRT somewhere along the base line
at a distance relative to the two surface indications,
usually as a smaller peak.
UT Equipment
The UT equipment, shown in figure 11-10, includes
a transmitter/transducer and CRT screen. These are the
two basic components of all UT equipment regardless
of make or model.
energy from the transmitter is transformed into
high-frequency mechanical energy by the transducer.
The transducer is held against a piece of metal with
some oil or glycerin (called a couplant) between the
contacting surfaces to prevent air from remaining
between them.
The high-frequency mechanical energy, in the form
of high-frequency sound, is transmitted into and
through the metal. After entering the metal, the sound
travels in straight lines in what is known as the beam
path. When the beam strikes the far surface of the piece
or strikes the boundary of a defect, the beam reflects
back toward the transducer. When the beam is
reflected, it leaves the metal in the same area it entered,
travels through the couplant, and enters the transducer
Figure 11-10.—Ultrasonic testing equipment.
Figure 11-11.—Principle of ultrasonics.
If the defect shows at a point one-half of the
distance along the base line (fig. 11-11) from the
entrance peak, then the defect will actually lie one-half
of the thickness of the piece from the entrance surface.
If the piece is 1 inch thick, then the defect will lie 1/2
inch below the surface. If the defect peak is high, the
defect is large (in a plane 90° from the beam); and if the
peak is small, then the defect is small. If the defect is
larger than the beam diameter, the defect surface will
bounce back ALL the beam, and the back reflection
peak will disappear. If the defect is smaller than the
beam diameter, some of the beam will be stopped and
bounced by the defect, and some will go on and be
bounced by the back of the piece. The CRT will then
show the near-surface peak, the small intermediate
peak, and a slightly reduced peak (at the back or far side
of the piece) at the right, or designated l-inch point, on
the base line.
Figure 11-12.—Angle beam testing.
Calibration Block
wedge to the transducer. This is known as the angle
beam method, shown in figure 11-12.
You need to determine the size of a defect, and
where possible, evaluate the nature of the defect.
This means that some reference or standard for
comparison (commonly called a calibration block) is
absolutely necessary. The most common practice is
to use a sample piece of material with a hole drilled
in it and compare defect signals obtained from the
calibration block. Calibration is the most important
part of ultrasonic testing, since it is essentially a
comparison test.
As you can see in figure 11-12, the sound beam
passes through the wedge and enters the part to be
tested at an angle. The sound beam will continue
to bounce at this angle until it is completely
scattered or absorbed by the material. Weld
inspections are performed when the sound has
made only one or two bounces. If a flaw is present
in the weld, as indicated in figure 11-12, some of
the sound beam will reflect back and show up as an
indication on the CRT screen.
The best scanning method is to move the
search unit forward and backward. Alternately
approach and move away from the weld a
distance sufficient to permit the sound to pass
through the full thickness of the plate and the
weld in an upward and downward path. The
search unit is also moved parallel to the weld
itself, as shown in figure 11-13. In this manner,
you will scan the complete volume of the weld,
following the same pattern along the weld, as
shown by the dotted line in figure 11-13.
Detecting, locating, and measuring defects are the
major requirements for weld inspection.
When testing welds for defects, you should use
the greatest possible direct reflection of sound.
This is easily done if the defects have a boundary
that lies parallel to the plane upon which the
transducer rests, and the face of the transducer lies
flat upon that plane. Such placement results in a
longitudinal (compressional) beam with its axis
normal to the surface boundary. To obtain the
greatest direct reflection, sound should strike a
surface boundary or defect boundary that lies at
right angles to its direction of travel. Since most
weld defects are rotated 90° from the surface, you
will need a way to change the direction of the
sound beam. You can do this by securing a Lucite
Nondestructive testing symbols specify the type of
test to be used and the extent to which the test will be
Figure 11-14.—Standard location of elements on a
nondestructive testing symbol.
Figure 11-13.—Scanning a weld.
Figure 11-15.—Arrow connecting the reference line and part
being tested.
performed. The four basic nondestructive testing
symbols are as follows:
Magnetic Particle
Liquid Penetrant
An assembled nondestructive testing symbol
consists of the following elements:
Extent of test
Basic testing symbol
Specification, process,
(N) Number of tests
or other reference
indicated by the test symbol on the side of the reference
line away from the reader, as shown in view B. Tests to
be made on both sides of the part are indicated by test
symbols on both sides of the reference line, as shown in
view C. When nondestructive testing symbols have no
arrow-side or other-side significance, the testing
symbols are centered on the reference line, as shown in
view D.
When a specification, process, classification, or
other reference is used with testing symbols, the
reference is placed in the tail, as shown in figure 11-17.
Specification, process, classification, or other reference
need not be used on testing symbols when the testing
procedure is prescribed elsewhere.
Each of these elements should be used as necessary.
They will have standard locations with respect to each
other, as shown in figure 11-14.
The arrow connects the reference line to the part to
be tested (fig. 11-15). The side of the part to which the
arrow points is called the arrow side of the part. The
side opposite the arrow is called the other side.
The location of testing symbols is shown in figure
11-16. Tests to be made on the arrow side of the part
are indicated by a test symbol on the side of the
reference line toward the reader, as shown in view A.
Tests to be made on the other side of the part are
Figure 11-16.—Location of testing symbols.
Figure 11-20.—Specify tests to be made all around.
Figure 11-17.—Location of specification, process,
classification, or reference.
Figure 11-18.—Specifying length and exact location of area to
be tested.
Figure 11-21.—Combining nondestructive testing symbols
and welding symbols.
Figure 11-19.—Specify number of tests to be made at random.
The length of the section to be tested is specified as
shown in figure 11-18. To specify tests of welds or parts
where only the length of the section need be considered,
the length in inches is shown to the right of the basic
test symbol (fig. 11-18, view A). To show the exact
location of the section to be tested as well as its length,
dimension lines are used as shown in view B. When the
full length of a part is to be tested, no length dimensions
need be shown on the testing symbol.
Fluid systems are hydrostatically tested during
initial construction, subsequent to repairs, and
periodically to verify the integrity of the system. All
piping sections that have been removed for repairs and
newly fabricated sections must be hydrostatically tested
before installation to make sure that there will be no
leaks under operating conditions. Operational tests are
also preformed, instead of hydrostatic tests, after certain
repairs involving mechanical joints. The basic purpose
of all such tests is to ascertain that the system can
perform its intended function safely and reliably. This
section will discuss hydrostatic tests, operational tests,
and the equipment used to conduct these tests.
If a number of tests are specified to be taken at
random, the desired number of tests are placed in
parentheses, as shown in figure 11-19.
To specify tests that are to be made all around a part,
the test-all-around symbol is used with the basic test
symbol, as shown in figure 11-20.
Nondestructive testing symbols may be combined
with the standard welding symbols previously
discussed. This feature increases the scope of all
welding symbols. The length of a section to be tested
can be indicated, and individual areas for testing can be
specified by means of these symbols. Figure 11-21
shows the combining of nondestructive testing symbols
and welding symbols.
Hydrostatic testing of piping systems is
accomplished whenever repairs are made to piping
system or any related components. Hydrostatic testing
of ships’ systems is required every 8 years, and should
be conducted before or during the early stages of a
scheduled major overhaul of the ship. Regardless of the
reason for testing, all hydrostatic testing is
accomplished in the same general manner using the
same equipment. Hydrostatic testing of systems or
components is commonly referred to as "H" pressure
tests. These tests of piping systems should be at a
pressure of 135 percent above the maximum system
design pressure, but in no case less than 50 psi. The line
drawing in figure 11-22 shows a simple hydrostatic test
setup and associated equipment.
Hydrostatic Testing Equipment
Shop hydrostatic testing of piping systems or
components should be conducted in an area that can be
secured from all traffic. This area should also provide
the operator protection in event of component failure.
When hydrostatic testing the ship’s piping system, set
up the equipment in an area that can be secured from all
unwanted traffic. The equipment required for
hydrostatic testing includes a pump, two pressure
gauges, two relief valves, a cutoff valve, blank flanges,
gaskets, and clamps.
PUMPS.—There is no specific requirements for
the type of pump to be used for hydrostatic testing. The
pump must be large enough to deliver the required
pressure and water volume to the system being tested.
Pneumatic pumps are the most common type of pump
used for hydrostatic testing and are operated by the
ship’s compressed air system. These pumps are usually
rated in gallons per minute.
PRESSURE GAUGES.—When performing
hydrostatic tests, use two independent pressure gauges.
These two gauges will indicate actual hydrostatic test
pressure. One of the gauges will be the master gauge
and the other will be the backup gauge. Use the master
hydrostatic test gauge readings as the true hydrostatic
test pressure throughout the test.
Master Gauge.—Master test gauges are used to
indicate actual hydrostatic test pressures. The scale
range of the master test gauge should be greater than the
maximum test pressure, but should not exceed 200
percent of the maximum test pressure. Master test
gauges shall have a valid calibration label according to
NAVSEA OD 54845, Metrology Requirements List.
Backup Gauge.—A backup gauge is used to check
and verify the accuracy of the master test gauge. Like
the master gauge, the backup gauge is also subject to
actual test pressure. The scale range of the backup test
gauge should also be greater than the maximum test
pressure, but should not exceed 200 percent of the
maximum test pressure. Backup test gauges shall also
have a valid calibration label according to NAVSEA OD
54845, Metrology Requirements List.
RELIEF VALVES.—Relief valves provide for
overpressure protection of the system or component,
equipment, and safety of personnel. The relieving
capacity, at test pressure of relief valves used for
Figure 11-22.—Hydrostatic test equipment and set up.
over-pressure protection and their inlet and discharge
piping, shall be greater than the capacity of the source
being used to pressurize the system. Relief valves are
classified as either the primary or secondary relief
Primary Relief Valve.—The primary relief valve
must be of the manual type that can be operated from
the control station. Usually the primary relief valve is
a manually operated valve with a drain to a sump or
other suitable drainage system. The person controlling
the source of pressure (pump operator) cannot also be a
relief valve operator.
pipe. After blanking off all openings of the pipe,
completely fill it with water through the nipple fitted to
the one blank flange.
SETUP.—System setup is similar to the hydrostatic
testing done in the shop. You will use a portable pump
with the required gauges and relief valves incorporated
into the pump control panel or on a separate manifold.
You should also take the following precautions when
hydrostatically testing shipboard systems:
When setting up a component for testing, each
outlet of the component must be blanked off
with blank flanges or other suitable blank
fittings. One fitting should be drilled and
tapped, and fitted with a nipple of suitable size
for connecting the hose from the hydrostatic
Secondary Relief—The secondary relief valve
may be either manually or automatically operated. The
secondary relief valve is usually located next to the
primary relief valve on a hydrostatic testing unit but
may also be remotely located. If the secondary relief
valve is of the manual type, another operator must be
stationed to operate this valve.
Protect equipment, tanks, gauges, and
machinery that would be subjected to a test
pressure higher than their specified test
pressure by disconnecting from the system, or
isolating from the test.
If the secondary relief is of the automatic type, test
the set point of the relief valves to be used. If necessary,
adjust the set point no more than 30 days before the
relief valves ae to be used for the hydrostatic test. In
conducting a 135 percent test, the set point of the relief
valve shall be no greater than 100 lb/in or 10 percent
above the test pressure, whichever is less.
Provide expansion joints with temporary
restraints, if required, or isolate them from the
Hydrostatic Testing Equipment Setup
Eliminate air pockets before any system is
pressurized for a hydrostatic test to prevent the
pressurization of gases in the system.
After assembling all required testing equipment and
checking calibration dates, you are ready to set up the
equipment for your test. Whether testing in the shop or
a ship’s system, the setup of the equipment is similar.
Both shop and system testing will be discussed in this
Verify that all valves and equipment in or
connected to the portion of the piping system
to be pressurized are in the required position or
shop testing is done in areas that are specifically
designed and built for hydrostatic testing. These areas
have installed pumps, gauges, and relief valves
permanently mounted in the area. The operating station
is isolated from the testing area to provide protection to
the operator in case of failure of the component being
Testing Procedures
After obtaining and setting up the equipment, you
are ready to begin testing of the component. Generally,
the sequence for testing is as follows:
When setting up a component for testing, each
outlet of the component must be blanked off with blank
flanges or other suitable blank fittings. One fitting
should be drilled and tapped, and fitted with a nipple of
suitable size for connecting the hose from the
hydrostatic pump. Use appropriate bolts to secure the
flanges or fittings with gaskets to all openings of the
1. Establish required prerequisites and initial
2. Align the system for testing.
3. Station the operator, manual relief valve
operator, and inspector. Two manual relief
valve operators may be required if a manual
relief valve is used for the secondary relief
repaired piping assembly and ships’ systems. You will
follow different testing parameters for each test.
4. Establish communication between the operator,
relief valve operator, and the inspector if their
stations are separated.
Testing Ships’ Systems.—For testing of a ship’s
system maintain the test pressure during hydrostatic
tests for at least 1/2 hour before inspection. If the
inspection is done prior to 1/2 hour, the system may not
be pressurized evenly and you may get an indication of
leakage due to valve packing and joint setting
occurring. Test pressure should be maintained at 135
percent of system design pressure but not less than 50
lb/in for the duration of the test. Some systems may
require tests more or less than 135 percent. Always
refer to the operator’s manuals, systems’ drawings, or
other applicable documentation for correct test
5. Pressurize the system slowly and incrementally,
checking for leaks at each increment.
6. Increase pressure to hydrostatic test pressure.
7. Perform required inspections.
8. Depressurize, remove temporary equipment,
and restore the system to its original
In the following section, we will look at component
pressurization, inspection requirements, and testing
Testing Repaired Piping Assemblies.—Always
test piping or piping assemblies (except halocarbon
refrigerant piping) removed for repair or replacement
before reinstallation. Test pressure, in most cases, will
be 135 percent of the system design pressure, but in no
cases less than 40 lb/in . Hydrostatic test pressure will
be held for a minimum of 15 minutes before inspection.
Hold this pressure while a complete inspection of the
piping assemble is made. Special attention should be
given to renewed parts and repaired sections. Some
assemblies may require tests of more or less than 135
percent. Always refer to the operator’s manuals,
systems, drawings, or other applicable documentation
for correct test pressures.
PRESSURIZATION.—During hydrostatic tests
of systems havin a maximum system pressure in
excess of 300 lb/in , raise the test pressure in increments
of approximately 25 percent of the final test pressure.
At each increment, make a check for leaks before
proceeding to the next higher pressure increment. The
final test pressure should be +2 to -0 percent of the final
test pressure but should not exceed 50 lb/in . For test
pressures less than 100 lb/in’, a +1 to -0 percent
tolerance is acceptable.
If any of the following events occur, you should
take immediate action to terminate the test and
depressuize the component:
Pressure gauge readings do not agree within 2
percent of maximum test pressure or are not
accurate within 2 percent of maximum test
HYDROSTATIC TESTS.—The criteria for an
acceptable hydrostatic test is that there should be no
leakage or permanent deformation of the
pressure-containing parts. This acceptance criteria is
determined by visual examination. The following are
exceptions to the no leakage criteria for acceptable
hydrostatic testing of ships’ systems only:
Changes in test pressure cannot be held
The leakage does not become hazardous to
Pressure gauge fails to respond to changes in
test pressure or gauge ruptures during the test.
VISUAL INSPECTIONS.—Visual inspections
are required at specified intervals as the pressure is
increased to the test pressure. Repaired areas that are
being tested should remain uninsulated to allow
examination for leakage.
The leakage can be adequately contained to
protect equipment.
The leakage is within the capacity of the
hydrostatic test pump to maintain pressure
throughout the test.
TEST DURATION.—The test duration for
hydrostatic testing of ships’ systems and of repaired
assemblies are different, although the end requirements
of the hydrostatic testing is the same for both the
Piping assemblies that have been repaired or
replaced require zero leakage.
Do not consider the test complete until all specified
inspection points have been recorded as satisfactory and
test pressure has been maintained. Correct or repair all
leaks. Rehydro all repaired assemblies or portion of
affected assemblies to the required test pressure.
Operational pressure tests (commonly called "J"
pressure tests) are performed periodically to determine
the integrity (leak tightness) of a system. Operational
tests are nothing more than visually inspecting the
system or repaired piping assembly while operating the
system at design pressure. Operational pressure tests
are also performed instead of hydrostatic tests after
certain repairs involving mechanical joints. The basic
purpose of an operational test, as with a hydrostatic test,
is to ascertain that the system perform its intended
function safely and reliably.
Periodic operational pressure tests should be
conducted under operating pressure (with the service
fluid) on all shipboard piping systems once a quarter.
At least once a year, conduct this test by pressurizing
the system one section at a time, to detect leaking valves
and to ensure proper operation of all the valves in the
This chapter has given you a basic knowledge of
radiographic tests, magnetic particle inspections, liquid
penetrant tests, ultrasonic inspections, hydrostatic tests,
and nondestructive testing symbols. Use this
knowledge along with the appropriate NAVSEA
technical manuals and publications, and on-the-job
experience under a qualified supervisor. You will soon
perform these tests in a professional manner and with
reliable results.
Upon completion of this chapter; you will be able to do the following:
Define some of the basic terms used in the layout and fabrication of sheet
Describe the basic techniques used to perform various sheet metal layout
operations and define the three types of plans
Recognize the various methods of pattern development
Describe some of the tools and equipment generally found in the sheet metal
shop, and describe their use and operation
Describe the safety procedures and equipment used in sheet metal fabrication
A BLUEPRINT is a duplicate of a drawing or
sketch. Usually, only accurate drawings are blueprinted.
These blueprints are furnished by the manufacturers of
the machinery installed aboard your ship and also by the
command concerned with the building and maintenance
of the ship on which you are serving.
As a Hull Maintenance Technician (HT), you may
be assigned to lay out and fabricate ventilation ducts,
drip pans, and other items made from sheet metal. In
this chapter, we will look at the tools and methods that
you will use for jobs of this sort. We will also look at
pattern development, the transfer of a pattern to sheet
metal, and the fabrication of the sheet metal projects.
If you have not done so, this is a good time to study
Blueprint Reading and Sketching, NAVPERS 12077-E
You must be able to read plans accurately, and this book
will help you to read almost any type of plan. A
satisfactorily completed job is your objective, and the
plans are essential guidelines. As you study this chapter,
you may find that you also need to review portions of
Use and Care of Hand Tools and Measuring Tools,
NAVEDTRA 12085, and Mathematics, Volume 1,
NAVEDTRA 10069-Dl.
NOTE: You will not be able to do the layouts in this
chapter unless you learn each step of each process as
you go along. Later in the chapter, you will simply be
instructed to carry out many of the procedures you were
taught earlier in this chapter. Before you can fabricate
an item, you must have a plan and be able to read it.
Your plan may be a sketch, a drawing, or a blueprint.
Later on, you will be expected to make your own
sketches and drawings.
The tools you will use most often to lay out sheet
metal jobs and patterns are the scratch awl, flat steel
square, circumference rule, straightedge, dividers,
trammel points, prick punch, and center punch. When
you make your practice layouts, you will probably be
restricted in the amount of sheet metal you can use. If
at all possible, use template paper instead of metal. This
material has a rosin-coated surface that is well adapted
A SKETCH is a rough outline of the structure to be
fabricated, giving dimensions and details of the job to
be done. The sketch includes such information as angles
to be used and the type of material required.
A DRAWING is similar to a sketch, but it is made
with mechanical drawing instruments and it is drawn to
to scribe and divider marks. If this type of paper is not
available, use heavy brown wrapping paper or
discarded chart paper, which you can get from the
navigator or quartermaster. When you use paper,
substitute a 4H pencil for the scribe and a pencil divider
for your regular layout dividers. Take good care of your
scribes, pencils, dividers, and rules because the
accuracy of your work depends upon them. After you
have made a few practice layouts, the importance of
accurate measurements should be clear to you. You will
have a feeling of satisfaction when your layout turns out
as you planned it. If it does not quite fit, you were
probably careless somewhere in your layout.
Figure 12-2.—Checking the square.
Figure 12-1 shows the correct way to scribe a line
on metal using a scratch awl and rule. When you scribe
your line, hold the scale or straightedge firmly in place.
Set the point of the scriber as close to the edge of the
scale as possible by tilting the scriber outward. Exert
pressure on the point and draw the line, tilting the tool
slightly in the direction of movement. For short lines,
use the steel scale as the guide. For longer lines, use a
circumference rule or a straightedge. When you draw a
line between two points, prick punch each point. Start
from one prick punch mark and scribe toward the center.
To complete the line, start from the other prick punch
mark and scribe towards the center as before.
Figure 12-3.—Drawing perpendicular parellel lines.
is shown in figure 12-3. Just clamp the straightedge
firmly to the base line. Slide the body of the square
along the straightedge, and draw perpendicular lines
through the desired points.
The FLAT STEEL SQUARE is useful for laying
out sheet metal jobs. Before using it, or at least at
periodic intervals, check the square for accuracy, as
shown in figure 12-2. When your square is off, your
work will be proportionately off, no matter how careful
you are. In parallel line development, use the flat steel
square to construct lines that are parallel to each other
as well as perpendicular to the baseline. This procedure
The COMBINATION SQUARE can be used to
draw a similar set of lines, as shown in figure 124. Use
Figure 12-1.—Scribing a line.
Figure 12-4.—Using a combination square.
an edge of the metal upon which you are working as the
base line. One edge of the head of the combination
square is 90 degrees and the other edge is 45 degrees.
Lay either edge of the head on the edge of the metal to
make either a 45- or 90-degree angle to the edge of the
When you need to scribe a circle with a radius larger
than your dividers, you will have to use TRAMMEL
POINTS. The points are adjusted as shown in figure
12-8. Set the left-hand point on one mark, sliding the
right-hand point to the desired distance, and tighten the
Combination squares are delicate instruments and
will be of little value if they receive rough handling.
Stow your tools properly when you are not using them.
Keep them clean and in tiptop shape, and you will be
able to construct 90-degree angles, 45-degree angles,
and parallel lines without error.
Use a protractor to construct lines for angles other
than 45 or 90 degrees. Mark the vertex of the angle on
the base line with a prick punch. (See fig. 12-5.) Set the
vertex of the protractor on the mark, and then scribe a
V at the desired angle (in this illustration, 70°). Scribe
the line between the vertex and the point located by the
V and you have constructed an angle of 70°.
Figure 12-6.—Setting the dividers.
When you mark a point with the PRICK PUNCH,
use very light taps with a small ballpeen hammer. The
smaller the mark you make (so long as you can see it),
the more useful and accurate that mark becomes.
Use DIVIDERS to scribe arcs and circles, to
transfer measurements from a scale to the layout, and to
transfer measurements from one part of the layout to
another. Careful setting of the dividers is of extreme
importance. When you transfer a measurement from a
scale to the work, set one point of the dividers on the
scale mark and accurately adjust the other leg to the
desired length, as illustrated in figure 12-6.
To scribe a circle or an arc, grasp the dividers
between the fingers and the thumb, as shown in figure
12-7. Place the point of one leg on the spot that will be
the center of the circle or arc. Exert just enough pressure
to hold the point at the center, slightly inclining the
dividers in the direction in which they are to be rotated.
Then rotate your dividers with both legs touching your
work to make your circle or arc.
Figure 12-7.—Scribing an arc or circle with dividers.
Figure 12-5.—Constructing an angle with the protractor.
Figure 12-8.—Setting trammel points.
is not cut, you will have difficulty forming the side of
the box. When you have the drip pan, or box, laid out,
form the pan by breaking (bending) the side up 90
degrees. If you have made all of your measurements
accurately, and have made your breaks on the line, the
upper edge will be even all around, like the one shown
in figure 12-11.
thumbscrew. Then scribe the arc or circle in the same
manner as with the dividers.
A STRETCHOUT is a pattern on a flat sheet that
has not been formed into a three-dimensional object.
Figure 12-9 shows three-dimensional objects being
formed from flat patterns. When jobs are laid out, you
will need to add allowances for edges and scams.
will be rectangular in shape, as shown in figure 12-12.
One dimension of the rectangle will be the height of the
cylinder, and the other dimension will be its
circumference. When you are given measurements for
a cylindrical job, however, you will be given the
diameter rather than the circumference of the cylinder.
You will have to find the circumference yourself.
A DRIP PAN is one of the objects you will have to
make. Some of these pans, or boxes, will be used around
the machinery in your shops. Take a look at them and
see how they were made. Some have welded seams.
Others are riveted and soldered. The welded seam is the
fastest and easiest to lay out, but the riveted and soldered
seam is by far the better of the two for sheet metal work.
The various methods of seaming will be discussed later
in this chapter.
The circumference may be determined by
computation or with a circumference rule.
Break out your layout tools. Select a piece of sheet
metal or template paper about 1 foot square. Lay out a
pan, or box, similar to that shown in figure 12-10. Make
the sides about 1 l/2 inches in height, and the bottom
about 9 inches square. Don't forget the tab if you are
going to join the seam by riveting. The angle for the
notch of the tab is 45 degrees (fig. 12-11). If this notch
Figure 12-11.—Layout of a box.
Figure 12-9.—Forming square and cylindrical shapes from
flat patterns.
Figure 12-10.—Layout of a box or a drip pan.
Figure 12-12.—Stretchout of a cylinder.
If you compute the circumference, multiply the
diameter by pi (π), or 3.1416. This formula is read as
C = πD. If the measurement is not critical, you can
round off pi to 3.14 or 3 l/7. Either way, the formula
will give you one dimension of your stretchout. The
height or length is your other dimension.
shape, which we will say is 12 inches. The second is the
circumference, which is computed as follows. Use the
formula C = πD + 2W. D is the diameter of the circle
that you would have if both curved ends of the shape
were put together. W is shown in figure 12-14. We will
assume that D = 5 inches, and W = 6 inches.
C= πD+2W
Another method is by the use of the circumference
rule. The upper edge of the circumference rule is
graduated in inches in the same manner as a regular
layout scale, but the lower edge is graduated, as shown
in figure 12-13.
C = 3.14 × 5+2 ×6
C = 15.7 + 12
C = 27.7
The lower edge gives you the approximate
circumference of any circle within the range of the rule.
You will notice in figure 12-13 that the reading on the
lower edge directly below the 3-inch mark is a little over
9 3/8 inches. This reading would be the circumference
of a circle with a diameter of 3 inches and would be the
length of a stretchout for a cylinder of that diameter. The
dimensions for the stretchout of a cylindrical object,
then, are the height or length of the cylinder and the
circumference. Do not forget that you will have to allow
for the scams.
We find that the circumference is 27.7 inches.
Therefore, our stretchout measures 27.7 inches by 12
Following are the procedures in using geometry for
making various types of layouts.
ANGLE. This is no problem at all if you have a true
steel square. We will describe three methods that you
may use to erect a perpendicular to produce a right angle
when you do not have a usable true steel square.
a flat-sided structure with rounded ends (fig. 12-14).
To figure the stretchout for this shape, you will need
two dimensions. The first is simply the length of the
1. For the first method, break out your dividers, a
scriber, and a straightedge. Draw a base line like the one
labeled AB in figure 12-15. Set the dividers for a
distance greater than one-half AB, then, with A as a
center, scribe arcs like those at C and D. Then, without
changing the setting of the dividers, use B as a center,
and scribe another set of arcs at C and D. Draw a line
through the points where the arcs intersect and you will
have perpendiculars to line AB, forming four 90-degree
or right angles. Not only have you constructed a
Figure 12-13.—Circumfcrcncc rule.
Figure 12-15.—Constructing a 90-degree angle by bisecting a
Figure 12-14.—Variation of a cylinder.
Figure 12-16.—Constructing a 90-degree angle at a given
perpendicular, but you also bisected, or divided, line AB
into two equal parts.
2. Use a pair of dividers to CONSTRUCT A
this skill quite useful in making layouts. Figure 12-16
illustrates one method for constructing a right angle at
a given point.
Suppose you have line XY with A as a point at
which you need to erect a perpendicular to form a right
angle. Select a point within the proposed angle that you
wish to construct. In figure 12-16 that point is C. Set the
dividers equal to CA, and using that distance for a
radius, swing an arc BAD with C as a center. Lay a
straightedge along the points B and C and draw a line
that will intersect the other end of the arc at D. Now,
draw a line connecting the points D and A and you have
constructed a 90-degree angle.
Figure 12-17.—Constructing a 90-degree angle by bisecting a
line at a given point.
stretchouts that are square or rectangular, such as a drip
pan or a box.
DIVIDERS, you will need dividers, a scriber, a
straightedge, and a sheet of template paper. You know
the length, width, and height or depth to which the pan
must be made. Now proceed as follows:
3. Figure 12-17 shows another way to construct a
perpendicular at a given point on a line:
Step 1: Take your dividers and place the point at
point B on line XY.
Step 2: Lay arcs on line XY at equal distances
from B on line XY. These arcs become points S and T
on line XY.
Step 1. Draw a base line. (See fig. 12-18.) Select a
point on this line for one corner of the drip pan layout.
Erect a perpendicular through this point to form a
90-degree angle (W in fig. 12-18).
Step 3: Before your next arcs are made, increase
the distance between your divider points. Set your
divider point at S on line XY. Lay arcs directly above
and below P on line XY. These arcs become points W
and M. Repeat this procedure from T on line XY
without adjusting your dividers. You will have
intersecting arcs at W and M.
Now, measure off on the base line the required
length of the pan (L in fig. 12-18). At this point erect
another perpendicular. You now have three sides of the
stretchout. Draw the fourth side parallel to the base line,
connecting the two perpendiculars that you have
erected. The fourth side will be drawn at a distance from
the base line equal to the width of the drip pan.
Now draw a perpendicular between the intersecting
arcs at W and M. You will have a right angle at B on
line XY.
Step 2. Now, set the dividers to mark off the depth
of the drip pan. You can use a steel scale to measure off
the correct radius on the dividers. Using each corner for
The three methods described in the preceding
paragraphs may be used to form 90-degree comers in
bisected a line, erected a perpendicular from a given
point on a line, and drew parallel lines by geometric
construction. Use those geometrical principles to do a
lot of layout problems rapidly and accurately.
You should also know how to BISECT AN
ANGLE. Angle ABC (fig. 12-19) is given. With B as a
center, draw an arc cutting the sides of the angle at D
and E. With D and E as centers, and with a radius greater
than half of arc DE, draw arcs intersecting at F. A line
drawn from B through the point F bisects the angle
OF EQUAL PARTS. You need only a straightedge and
a compass. Figure 12-20 illustrates the dividing of a line
into 10 equal parts. To divide line AB into 10 equal
parts, draw random line CB from B at a convenient
acute angle to AB. Set a compass to a spread less than
one-tenth of the length of CB, and lay off this spread 10
times from B on CB. Project the intermediate points of
intersection on CB to AB by lines parallel to the line
between the 10th point of intersection and A. The
projected points of intersection divide AB into 10 equal
OF A CIRCLE into six approximately equal parts. Set
the dividers for the radius of the circle and select a point
Figure 12-l8.—Laying out a drip pan with dividers.
a point, swing a wide arc like the one shown in the
second step in figure 12-18.
Step 3. Extend the end and side lines as shown in
the last step in figure 12-18, andcomplete the stretchout
by connecting the arcs with a scriber and straightedge.
Figure 12-19.—Bisecting an angle.
Step 4. Now lay out tabs like those shown in figure
12-11. Their size is determined by the diameter of the
rivet, which in turn is determined by the thickness of the
sheet. All that remains to be done now is to transfer the
pattern to the sheet, cut the metal, and form it.
You have seen how a pan can be laid out without a
steel square by the use of geometric construction. You
Figure 12-20.—Dividing a line into any number of equal parts.
Figure 12-21.—Dividing a circle into six equal parts.
on the circumference for a beginning point. In figure
12-21, point A is selected for a beginning point. With
A as a center, swing an arc through the circumference
of the circle like the one shown at B in the illustration.
Use B, then, as a point, and swing an arc through the
circumference at C. Continue to step off in this manner
until you have divided the circle into six equal parts. If
the points of intersection between the arcs and the
circumference are connected as shown in figure 12-21,
the lines will intersect at the center of the circle, forming
angles of 60 degrees.
Figure 12-22.—Layout of a square or rectangular elbow.
sides of the elbow, the throat being the inside piece and
the heel the outside piece. Set the dividers at exactly 1
inch, and step off the heel and throat arcs as shown in
view C of figure 12-22. If there is a distance of less than
1 inch left at the end of the arc, measure it with another
pair of dividers or a scale. To make the stretchout of the
heel and throat, lay out one piece of metal equal to the
height of the elbow (H in view A, fig. 12-22) and equal
in length to the number of steps taken with the dividers,
plus the fraction of an inch left over. One stretch out will
be the heel and the other the throat. You can assemble
this elbow by welding, in which case you do not need
to allow for tabs. But welding will cause a thin section
to warp, so you may need to use some of the other
standard methods for joining this type of work.
If you need an angle of 30 degrees, all you have to
do is to bisect one of these 60-degree angles by the
method described earlier in this chapter. Bisect the
30-degree angle and you have a 15-degree angle. You
can construct a 45-degree angle in the same manner by
bisecting a 9O-degree angle. In all probability, you’ll
have a protractor to lay out these and other angles. But
since you may not always have a steel square or
protractor available, it’s a good idea to know how to
construct angles of various sizes and to erect
So far, your practice jobs have been laid out to be
formed with the edges left as they are. Very few of your
jobs in the shop will actually be fabricated in this
manner. Edges are formed to improve the appearance
of the work, to strengthen the piece, or to eliminate a
raw edge that could cut someone. These edges may be
formed from the metal itself by inserting wire or by
attaching a band or angle iron. The kind of edge that you
will use on any job will be determined by the purpose,
size, or strength of the edge needed.
at figure 12-22. View A shows you what the completed
job should look like. Now, to make your layout for this
job, draw the base line OZ shown in view B. Set the
dividers for a distance equal to the width of the cheek.
This distance forms the throat radius. This rule will not
always apply, as it must often be governed by the
amount of space available to make the turn with the
elbow. Now, with O as a center, scribe the arc YU. To
get the heel radius, add the width of the cheek to the
throat radius. Using 0 as a center, scribe the arc ZT.
These layouts, when cut, will form the cheeks, or sides,
of the elbow. The next operation is to lay out the heel
and throat pieces. These arc the other two of the four
The SINGLE-HEM EDGE is shown in figure
12-23. This edge can be made in any width. In general,
the heavier the metal, the wider the hem is made. The
allowance for the hem is equal to its width (W in fig.
LAP SEAMS are shown in figure 12-26. They may
be of three kinds: the plain lap seam; the offset, or
“joggled,” lap seam; or the corner lap seam. Lap seams
may be joined by drilling and riveting, by soldering, or
by a combination of both riveting and soldering. To
figure the allowance for a lap seam, you must first know
the diameter of the rivet that you plan to use. The center
of the rivet must be set in from the edge a distance of
two and one half times its diameter. The total allowance,
then must be five times the diameter of the rivet that you
are going to use. Figure 12-27 shows the manner in
which a plain lap and a corner lap are laid out for
seaming with rivets. For corner seams, allow an
additional 1/16 inch for clearance.
Figure 12-23.—Single-hem edge.
GROOVED SEAMS are useful in the construction
of cylindrical shapes. There are two types of grooved
seams-the outside grooved seam and the inside
grooved seam (fig. 12-28). The allowance for a grooved
Figure 12-24.—Double-hem edge.
The DOUBLE-HEM EDGE (fig. 12-24) is used
where additional strength is needed or when a smooth
edge is desired inside as well as outside. The allowance
for the double-hem edge is twice the width of the hem.
A WIRED EDGE (fig. 12-25) will often be
specified in plans. Objects such as ice-cube trays,
funnels, garbage pails, and other articles formed from
sheet metal are manufactured with wired edges to
strengthen and stiffen and to eliminate sharp edges. The
allowance for a wired edge is 2 l/2 times the diameter
of the wire used. For example, if you are using wire that
has a diameter of l/8 inch, multiply l/8 by 2 l/2 and
your answer will be 5/16 inch. This is the amount you
will allow when laying out sheet metal for the wired
Figure 12-26.—Lap seams.
When you made your layout for a drip pan or box,
you were told to allow for a tab for seaming with rivets.
This method of joining sheet metal is known as lap
Figure 12-27.—Layout of lap seams for riveting.
Figure 12-25.—Wired edge.
seam is three times the width (W in fig. 12-28) of the
lock, one-half of this amount being added to each edge.
For example, if you are to have a 1/4-inch grooved
seam, 3 × l/4 = 3/4 inch, which is the total allowance;
l/2 of 3/4 inch = 3/8 inch, which is the allowance you
will add to each edge.
Figure 12-28.—Grooved seams.
Figure 12-29.—Pittsburgh lock seams.
The PITTSBURGH LOCK SEAM (fig. 12-29) is a
very useful corner seam that is used to advantage in
rectangular ventilation lines, elbows, and boxes. At first
glance, the seam appears to be quite complicated, but
like lap and grooved seams it consists of only two
pieces. The two parts are the flanged edge and the
pocket with the projected edge, which is known as the
locking flange after it has been bent over. After the
pocket is formed, the flanged edge is inserted into the
pocket, and the projected edge is then bent over the
flanged edge. It then forms the locking flange that
completes the Pittsburgh lock seam.
The allowance for the pocket and projected edge or
locking flange is W + W + 3/16 inch. W is the width or
depth of the pocket with 3/16 inch for the locking
flange. The width of the flanged edge is l/l6 inch less
than W to ensure a good tight fit. For example, if you
are laying out a l/4-inch Pittsburgh lock (fig. 12-30, top
view), your total allowance should be l/4 inch + l/4
inch + 3/16 inch, or 11/16 inch for the edge on which
Figure 12-30.—Layout of Pittsburgh lock seam.
you are laying out the pocket, and 3/16 inch on your top
piece for the flanged edge.
Your first 90-degree bends will be on line ADB, and
the next ones will be on line CDE. But before you can
make your bends, you will have to make your notch.
To make your notch, lay out your dimensions for
the length and the width. Make sure you include the
width the flange in your layout. Next lay out line
ADB, which will be the width of the flange. Then lay
out line CDE where your main bend will be, as shown
in part V of figure 12-32. Next, bisect angles ADE and
BDE on the flange, as shown in part W. Your final step
prior to bending is to cut out your V-notch (angle FDG),
as shown in part X of figure 12-32. Views Y and 2 show
the bends being made.
Notching is the last but not the least important step
to be considered when you lay out a job. A notch is the
spot on a piece of sheet metal that is cut out to allow the
forming of a bend without the metal binding. Before
you can mark a notch, you will have to lay out the
pattern and add the seams, laps, or stiffening edges. If
the patterns are not properly notched, you will have
trouble when you start forming, assembling, or
finishing the job.
There is no definite rule for selecting the proper
notch for the job. But as soon as you can visualize the
assembly of the job, you will have no trouble
determining the shape of the appropriate notch. If the
notch is made too large, a hole will be left in the finished
job. If the notch is too small, or not of the proper shape,
the metal will overlap and bulge at the seam or edge. Do
not worry too much if your first notches do not come
out very well; practice and experience will take care of
When you are making an inside flange on an angle
of MORE or LESS than 90 degrees, you will have to
use a modification of the full V-notch to get flush joints.
The angle of the notch will depend upon the bend angle.
A modified V-notch is shown in figure 12-33.
A SQUARE NOTCH is probably the first one you
will make. That is the kind you were instructed to make
in your practice layout of a box or drip pan. Take a look
around the shop to see just how many different kinds of
notches you can see in the sheet metal shapes.
SLANT NOTCHES are cut at a 45-degree angle
across the corner, when a single hem is to meet at a
90-degree angle. Figure 12-31 shows the steps in
forming a slant notch.
A V-NOTCH is used to seam the ends of boxes. You
will also use a full V-notch when you construct a bracket
with a toed-in flange or for similar construction. The
full V is shown in figure 12-32.
Figure 12-32.—V-notch.
Figure 12-33—Modified V-notch.
Figure 12-31.—Slant notch.
Figure 12-34.—Wire notch in cylindrical layout.
If all work that you were assigned to do consisted
of laying out and fabricating drip pans, boxes, lockers,
and straight sections of cylindrical and rectangular
ventilation lines, your work would be much easier. Your
layout would consist of nothing more than straight-line
angular development, allowances for seams and edges,
and visualizing the notch needed. But you will have to
construct ventilation systems, or at least make repairs
to those systems. This work calls for elbows and tees,
which cannot be laid out unless you know how to do