MOTOR FOR MACHINE TOOLS

MOTOR FOR MACHINE TOOLS
>5
B
CENTS
3 Dlfl fi43
MOTOR DRIVE FOR
MACHINE TOOLS
WITH A CHAPTER ON WIRING
FOR MOTOR-DRIVEN MACHINERY
MACHINERY'S REFERENCE BOOR NO. 115
PUBLISHED BY MACHINERY. NEW YORK
MACHINERY'S REFERENCE SERIES
EACH NUMBER IS A UNIT IN A SERIES ON ELECTRICAL AND
STEAM ENGINEERING DRAWING AND MACHINE
DESIGN AND SHOP PRACTICE
NUMBER
115
ELECTRIC
MOTOR DRIVE FOR
MACHINE TOOLS
CONTENTS
Application of Motors to Machine Tools
Wiring on Motor-driven Machinery
-
3
-
-
Copyright, 1913, The Industrial Press, Publishers of MACHINERY,
140-144 Lafayette Street, New York City
-
29
CHAPTER
I
APPLICATION OF MOTORS TO MACHINE TOOLS*
For the shop where electric power is already installed, all kinds
machine tools may be purchased completely equipped with individual motors.
When, however, it is desired to institute a change in a
shop that has been employing belts and shafting, and to substitute
electric power, it becomes necessary to consider each of the belt-driven
of
tools separately, so as to secure as nearly as possible the
that are obtained with the tools built for motor drive.
same results
At the same
time excessive expenditures in the alterations must be avoided. It is
the purpose of this article to outline the principles of motor application, and to suggest methods by which the belt-driven tools may be
accommodated to motor drive.
The first problem to consider
is that of the transmission of the
In large plants, covering acres of ground, alternating current
is employed in order to permit the use of high voltages with the
corresponding saving in the copper used for wiring. In plants consisting of but a few buildings, grouped fairly close together, the use
of direct current possesses advantages in variable speed possibilities
that far outweigh the gain to be secured by the use of the high-voltage
It is, therefore, the general practice at the
alternating current.
present time to use 230-volt direct current for the operation of plants
of the nature of machine shops, in which a large part of the load
will consist of motors driving tools requiring variable speed.
Where
long transmissions make the distribution of power by alternating
current a necessity, a motor-generator may be installed at the point
of distribution for the purpose of supplying direct current to the
This is often the system employed in the
variable-speed motors.
case of railway shops which are spread out over a considerable
territory and contain a large proportion of constant-speed tools. Here
the transmission current is 440 volts, alternating, and the constantspeed motors are operated on this current, while the motor-generator
supplies 230-volt direct current for the operation of the variablespeed motors.
Types of Motors
power.
In the first place the three types of direct-current motors should be
thoroughly defined, so that the proper type may be selected for the
particular tool to which the motor is to be applied. These three types
are series-wound, shunt-wound, and
The series-wound motor
is
compound-wound motors.
one in which the
.
Mainly from an article by Georgo
II.
winding is in
armature circuit,
armature passes
field
series with, or forms a direct continuation of, the
so that all of the current that passes through the
Hall in MACHINERY, June, 1912.
347581
No.
4
llo-^MOTOR DRIVE
The amount of current drawn from the line
also through the fields.
by a motor depends upon the work, or horsepower, which the motor
It therefore follows that in the series motor the
is developing.
strength of the fields will depend upon the load which is placed on
the aotor, and as the speed of the motor depends inversely upon the
field strength, the speed of the series motor will be inversely proportional to the load. Since the speed of a motor also depends upon
the voltage that is impressed upon the armature, the speed of a series
motor may be controlled by introducing resistance in series with
the armature, and this is accomplished by means of a controller
which is used also for starting the motor. The use of the controller
enables the operator to start the motor slowly under light loads,
and also prevents too great a flow of current when starting under
heavy loads. The characteristics of the series motor are heavy starting torque and a speed dependent upon the load.
The shunt-wound motor is one in which the field winding is connected across the main lines, or is said to be in shunt with the
armature circuit. The amount of current passing through the fields
proportional to their resistance, and, except in the case
variable-speed motor which will be treated later, remains
This results in a
practically constant under all conditions of load.
is inversely
of
the
constant-speed motor whose output, in horsepower, is dependent upon
The
the current, in amperes, which passes through the armature.
characteristic of the shunt-wound motor is approximately constant
speed under
all
conditions of load.
The compound-wound motor is one having both a shunt and a
The shunt field is connected to the main line
series field winding.
as in a shunt motor, while the series field is in series with the
armature and carries all of the current passing through it as in the
series motor.
The field of an average compound motor is composed
of about eighty per cent of shunt winding and twenty per cent of
series winding, although this proportion may be varied to suit the
class of work for which the motor is to be used.
The speed of a
is more nearly constant than that of a series motor,
but the drop in speed from no load to full load is considerably more
than in a shunt motor, owing to the action of the series part of the
The characteristics of the compound motor partake of
winding.
those of both the series and the shunt motors in about the same
degree as the relative proportion of the two windings composing the
compound motor
field.
Selection of Direct- current Motors for Factory Use*
The prospective purchaser should ascertain accurately the desired
speed or speeds of the machine to be driven, and the maximum horsepower as well as the average horsepower required to do the work.
The speed or speeds of the driven machine may be ascertained by tests
conducted with an experimental motor, or from data furnished by the
Often
builder of the machine, where such information is available.
* Abstract of an article by Earle D.
tember, 1911.
Jackson
in
the
"Engineering Magazine," Sep-
APPLICATION OF MOTORS TO MACHINE TOOLS
5
motor drive is to replace a steam drive, or individual motor
drives are to replace an existing motor-driven group drive, in which
cases the speeds are easily determined.
the
Horsepower Required
to do the work should be determined
The purchaser may rent an experimental
power required, which is probably the
The group drive gensolve the problem.
testing be done, as the amount of power
The horsepower required
as accurately as possible.
motor and ascertain the
most satisfactory way
to
requires that this
required under actual conditions
erally
for a group of machines of difand sizes is problematical, and the information cannot
be obtained from the machine manufacturers as can often be done in
It should be rememthe case of an individually driven machine.
bered in this connection that from the input to the test motor as
measured with a wattmeter, or with a voltmeter and ammeter, should
be subtracted the test-motor losses, as the motor to be purchased
ferent kinds
rated on horsepower output or brake-horsepower.
Money spent
the accurate determination of the amount of power required is
wisely expended a fact often overlooked by the factory manager.
Machine-tool builders, motor manufacturers, and central stations
is
in
are often called upon to supply the information as to how large
a motor should be. Without accurate data, the machine-tool builder
often overestimates the horsepower required for driving his tools,
in order to be on the safe side, with the result that the motors run
at one-quarter
duced
to
efficiency.
one-half load day
The
electrical
and day
in
losses,
together
out,
at greatly re-
with interest and
depreciation on the unnecessary extra investment, may amount to
It certainly behooves
a considerable sum in a large installation.
the machine-tool builder to have on hand (and, of course, many
of them do) accurate data acquired from carefully conducted tests,
covering the performance of his motor-driven machines under all
conditions of load and speed.
The motor manufacturer often has
in his
own establishment
in-
dividual maciiine-tool drives and group drives similar to those of
the prospective purchaser, in which event he can supply the necessary
information as to the size of the motor.
Many up-to-date central
amount of data on power required for difmotor drives, derived from actual tests under working conditions, which are always available to a prospective power consumer.
The piece-worker requires a relatively larger motor for the same
tool than does the operator working by the day.
In the former case,
heavy cuts at the higher speeds will be the rule, together with quicker
starting and more continuous running of the motor, as the pieceworker crowds his machine to the limit, and must be provided with
ample motor capacity. Nothing is more discouraging to a workman
than to find out that the motor will not perform all the work he
stations also have a vast
ferent
requires of
it,
or
is
continually giving trouble.
No.
6
115
MOTOR DRIVE
Group Drives*
A
few years ago when the electric motor drive began to take a
prominent place in manufacturing plants, many factories changed
from the old method of belting the engine to a large drive shaft,
which was connected by belts to long lines of shafting throughout
the plant, to the individual motor drive having a separate motor attached to each machine. The owners soon discovered that this made
a very expensive installation, and this form of drive, although -the
most flexible, is gradually giving way to the group drive for light
machine shop work. In the group drive a motor drives a short length
This arof lineshafting which, in turn, drives the machine tools.
rangement makes the first cost considerably less than that of the individual motor drive, and if planned systematically it is almost as
flexible as the latter method.
The best arrangement for the group drive is to divide the machine shop into small units, having a motor for each department or
The lineshafting should be as short as
each kind of machines.
possible and the motors placed in accessible positions, so that they
can be watched and easily replaced in case of a breakdown. A small
platform makes an excellent mounting for a motor, as it can be easily
Experience has proved
inspected and removed if found necessary.
that motors suspended from the ceiling do not receive as careful
attention, and a further disadvantage of this method of mounting lies
in the fact that the motors are difficult to replace when set up in this
way. With the proper equipment, a motor can be removed from a
platform and a new motor installed in less than fifteen minutes.
By carefully planning a group drive system, all the lineshafting can
be run at the same speed and a standard size motor adopted for the
entire shop. This does away with the necessity of carrying a number
of different sized motors in stock and standardizes the motor equipment of a factory.
impossible to obtain reliable data for figuring the proper
to drive machine tools.
During the installation of
mechanical equipment in an automobile engine factory, the machine
shop was carefully laid out and a copy of the drawing, together with
the sizes of machine tools, kind of work, speed and other technical
information were sent to the different machine tool builders with the
request that they give the exact power requirements for their machines
when operating on the group drive system. The replies were carefully
It is often
size
of motors
tabulated and after a careful analysis, it was shown that machine
tool builders were giving the same results for group drive as for the
individual drive, overlooking the fact that some of the machines would
be idle and others consuming only a small amount of power at the
time when the remaining machines were absorbing the maximum
amount
of power.
These .conditions all tend to equalize one another,
so that the average power used by each machine would be considerably less for the group drive than the maximum power demanded
for the individual drive.
From an
article
by Harry
C.
Spillman
in
MACHINERY, June,
1913.
APPLICATION OF MOTORS TO MACHINE TOOLS
No.
8
115
MOTOR DRIVE
Careful tests which have been made since the machine shop was
placed in operation show that the shop takes less than one-fifth of
the power recommended by the machine tool builders, or in other
words, they were figuring over five times too high for the group drive.
The accompanying
shows
that
the
table
gives
lineshafting
the
and
results
of
the
countershafting
tests.
consume
It
also
thirty
per cent of the total power, and the total friction losses absorb seventytwo per cent of the total power. This makes a forty-two per cent
loss of power from the countershafting to the machine tools, and only
twenty per cent of the total power is utilized in doing work. The
In the table
electrical loss shows eight per cent of the total power.
Total average power per
there are two items mentioned as follows:
machine, deducting idle machines; total average power per machine,
These items include all the mechanical
including idle machines.
power of that department, such as lineshafting, countershafting, machine friction and power consumed in doing work on the machines.
In the first case this total power is equally divided among all the
machines which are in operation. In the second case it is divided
equally among all the machines, both running and idle. The electrical
losses are omitted in all cases.
Having determined the speeds of the driven machines and the
horsepower required to do the work under all conditions, a knowledge of the various types of direct-current motors is the next essential
in order that a motor may be selected which will fulfill the conditions
required of it in the most acceptable manner.
Selection of Motors
To determine the type
classes of tools in the
of motor to be employed for the different
machine shop, the character of the power re-
quirements of the tools should be carefully analyzed. In the case of
lathes, boring mills, milling machines, etc., in which the work of
cutting is continuous, it will be seen that the tool is required to run
at a speed which can be adjusted to the character of the work being
machined, and when so adjusted will remain practically constant.
the tool is usually started before the work of actual cutting
that no excess of power is needed to start. The foregoing
requirements correspond to the characteristics of the shunt motor,
and for this class of work this motor should invariably be used.
Also,
begins,, so
In the case of planers, shapers, slotters, etc., the work is intermittent, being far greater at some portions of the stroke than at
others, and for this class of work the compound motor is best suited.
The same type of motor is also used for the operation of punches,
shears and other tools having heavy flywheels, as the motor will
slow down at the period of greatest load, which is just after the
The actual cut is effected through the
completion of the stroke.
inertia of the flywheel, and the maximum load on the motor is that
of accelerating the flywheel and bringing it back to normal speed
after
it
has carried the tool through the work.
APPLICATION OF MOTORS TO MACHINE TOOLS
9
When operating hoists and cranes, the motor must be started under
the full weight of the load to be handled and at the same time slowly
enough to prevent the shock of too sudden acceleration. These requirements are best met by the series motor with a controller having
a heavy starting resistance, as it provides high torque at low speeds.
This type of motor is also used for auxiliary purposes, such as raising
the cross-rails of planers and boring mills, traversing the carriages
of large lathes, and elevating the tables of horizontal boring mills.
Types of Motors
for Different
Requirements
The general classification of direct-current motors now included in
the standard product of nearly all motor manufacturers is as follows:
Approximately constant speed, no
load to full load
j
Semi-constant speed,
full load
Adjustable
speed,
proximately
adjustment,
no load
to
(
Compound motor.
remaining apfor one
load
Shunt motor.
Shunt-commutating pole motor.
\
constant
no
j
to
/-
\
full
J
'
load
Adjustable speed, semi-constant
for one adjustment, no load to
full load
(
J
Shunt motor, with adjustable
field
resistance.
Shunt-commutating pole motor
with adjustable field resistance.
Compound motor, with
shunt
field
resistance
adjustable
-
(
Varying speed, varying with the
load
Series motor,
j
)
Series-commutating pole motor.
Constant-speed shunt motors are, of course, used for the operation
of groups of machines that are driven by a common countershaft,
but for individual drive the constant-speed motor is little used, as
one of the greatest advantages of individual drive is the ability to
vary the speed of the tool to suit the requirements of each piece
being machined. This naturally brings up the question as to where
the line should be drawn between tools that should be arranged for
group drive and those which may advantageously be equipped with
individual motors.
No fixed rules can be laid down in answer to
this question, but, in general, it is customary to group the smaller
tools, as the initial expense of separate equipments for such tools
bench
tool grinders, emery wheels, and sensitive drills,
In the
exceeds the cost of the tools themselves.
tool-room, also, the value of individual equipment is questionable,
as the work on each tool is intermittent and there is not the demand for the high efficiency from the tools that obtains in the case of
tools used in the manufacturing departments.
If the product of a
given tool is especially valuable, or forms a very important part of
the shop's output, the first cost of the drive is of minor consideration, and an individual equipment which will secure the greatest
output is warranted.
as
drills,
often equals or
10
No.
115
MOTOR DRIVE
Variable- speed Motors
Variable-speed motors, in the generally accepted use of the term,
are, strictly speaking, adjustable-speed motors, in that the speed
may be adjusted by means of a controller. There are two methods
common
in
complished.
practice by which this adjustment of speed may be acThese are known, respectively, as armature regulation
and fieki control.
The first method consists of introducing resistance in series with
the armature circuit, thereby reducing the voltage that is impressed
on the armature. With constant field strength, as in a shunt motor,
the speed of the motor will be directly in proportion to the impressed
If the load on a motor remains constant, the speed will
voltage.
be inversely proportional to the resistance inserted in the circuit,
as the torque is in proportion to the current in amperes, and the
From the
voltage equals the amperes divided by the resistance.
foregoing it will be seen that if the motor load varies, the voltage
and, therefore, the motor speed will, with a fixed resistance, vary
with the load.
of the motor when armature control is
the torque, or turning effort, is proportional to the amperes drawn by the motor, while the horsepower is a function of the
of the volts and the amperes.
Thus a motor developing a
* product
Now, consider the output
employed;
given horsepower draws from the line a definite amount of current
and produces a torque corresponding to that horsepower. If, now, we
cut the speed in half, by halving the impressed voltage, while the
torque remains the same, the product of the volts by the amperes
will be but one-half, and the motor will be delivering but one-half
its former horsepower, although it will be drawing just as much
current as when delivering the full horsepower.
Thus it will be
seen that this method of control is uneconomical and gives a speed
varying with the load, while the demand of most machine tools is
for a drive that will give a desired speed regardless of the load.
In
employing the method described it is almost impossible to secure
slow motor speeds with very light loads. For this reason this method
of control is but little used in connection with machine tools.
The second method, that of field control, is most generally used
for motors employed in the operation of machine tools.
With the
voltage impressed on the armature constant, the speed of a motor
be inversely proportional to the strength of the fields.
This
strength is directly proportional to the ampere-turns in the
field, and as the actual turns of wire must remain constant, the
ampere-turns may be easily regulated by inserting resistance in series
with the field winding and thus decreasing the current in amperes
will
field
passing through the field. The torque of the motor is, in this case,
proportional to the field strength, and, as the field strength varies
inversely as the speed increases, the horsepower of the motor will
remain practically constant.
Considering the average class of tools, such as lathes, boring mills,
we can readily see that the foregoing motor characteristics
etc.,
APPLICATION OF MOTORS TO MACHINE TOOLS
11
correspond to the requirements. When the cutting tool is run at a
high speed, the cut taken by the tool is light, and when taking heavy
cuts, the speed is slow, thus calling for a practically constant horsepower throughout the working range of the tool.
As the field current is but a small proportion of the total current
used by the motor, the total current consumption of motors using this
type of control is practically in proportion to the work being done, so
that this is an economical method. The speed, also, being regulated
field strength, is independent of the load, so that for a given
controller position it will be practically constant regardless of the
power developed. As a matter of fact, the shunt motor with constant
by the
field strength will vary about 5 per cent from no load speed to full
load speed.
Open or Enclosed Motors
The question whether to employ the open or enclosed motor often
The metal covers of closed motors reduce the efficiency and
arises.
capacity of the motor by preventing free circulation of air around
the active elements of the motor.
Working conditions will usually
decide whether it is possible to use the open motor, which is, of
course, the desirable practice, or whether the presence of excessive
dust makes it necessary to enclose the moving parts of the motor
The partially or semi-enclosed motor should
partially or completely.
not be placed in a concealed position for the reason that it is then
certain to be neglected in an ordinary factory. The perforated covers
and wire screens will close up by dust and dirt, and as the result the
semi-enclosed motor becomes virtually a totally enclosed motor with
a semi-enclosed rating and consequent trouble.
General Considerations
Vertical motors are
made
in a
number
of sizes, but are only to be
makes it apparent that
they possess great advantages over the standard or horizontal type,
as vertical motors are troublesome to keep in running order and
They are not generally kept in stock by
require greater attention.
local dealers, and the motor, as well as repair parts, must be replaced
from the factory stock at the risk of the usual delay in shipment.
Manufacturers' standard sizes and speeds of motors should be chosen
recommended when the nature
of the drive
possible, in preference to motors of special sizes and speeds,
as prices, time of delivery, and general performance of the former
In
will be found to be more favorable than those of special design.
many cases, it will be found impossible to select from the standard
wherever
and speeds of a single motor manufacturer only, all the motors
which are required, and in this case there is no valid reason why
the order should not be divided up and the motors purchased from the
builders whose standard product meets the required conditions.
The direct-current voltage now practically standardized for factory
use is 220 volts. This voltage is both economically and operatively
superior for direct-current motor systems to that of 110 volts somesizes
times employed.
No.
12
115
MOTOR DRIVE
Types of Drives
Having determined the horsepower and selected the type or types
of direct-current motors desired, the best means to employ in driving
the machines is the next problem that is confronted. In considering
a belt drive, a greater pulley reduction than 5 to 1 is not to be recommended. Idlers to increase the arc of contact, or countershafts between the motor and the driven machine to reduce the initial speed
of the driver, are doubtful expedients, unless the amount of power
used is very small. It is an easy matter to design a belt 6>ive of
this kind in which 20 to 30 per cent of the power of the motor is
wasted between the motor and the driven machine.
Direct-connected drives, gear drives, and silent chains constitute
a list of positive drives from which it should be possible to select
a satisfactory method of driving a machine from a motor, in which
The
safety, reliability, and economy of operation are all present.
direct-connected drive is the ideal drive, as it eliminates all interIn a great many cases, howmediate power-absorbing apparatus.
ever, the use of the direct-connected drive necessitates the employment of a special motor. It is unfortunate, in this respect, that
machine-tool builders and motor manufacturers often disregard each
other when it comes to the selection of standard speeds for their
respective machines, although they are collaborating more than they
The silent chain as a means of driving machines
did formerly.
The early types of silent chains were
is coming into wider use.
rapidly depreciated, and in many installations were far
In point of efficiency, the silent-chain drive
"silent."
stands next to the direct-connected drive. The main objection to the
gear drive is its excessive noise, but this may be overcome to a large
expensive,
from being
degree by the use of a rawhide pinion.
Specifications
Specifications should be drawn which state in detail the number
of motors required, the horsepower of each motor, the desired motor
speed or speeds, together with the speed or speeds of the corresponding driven machine, and the name or description of the machine,
giving the number of hours of its probable use per day; whether the
motor is to be of the open, semi-enclosed, or enclosed type; the line
voltage; details of the motor drive, including pulleys, gears, chains
and sprockets, of both driver and driven machine; and whether the
motor foundations are to be included in the contract price. Specifications should be submitted to at least three reputable motor manufacturers for quotations, giving cost complete in the case of each
separate motor, weights and mechanical sizes of motors offered, efficiencies at one-quarter,
all
one-half, three-quarters,
load,
commutation at
all
and
full
loads, for
speed regulation from no load to full
loads and speeds, temperature rise, overload
ranges of speed called
for,
capacity, times of delivery, and description of all starting and field
or other rheostats to be furnished, as well as complete description
Each one of the foregoing items should be known,
of each motor.
APPLICATION OP MOTORS TO MACHINE TOOLS
if
intelligent comparison and
may also call for a test of each
selection are to be made.
The
13
speci-
motor purchased, to be
made by the purchaser or his engineer after the motors are in place
and before final acceptance, to demonstrate whether or not all of the
required conditions have been fulfilled.
fications
TABLE
I.
Frame
TYPICAL LINE OF VARIABLE-SPEED SHUNT MOTOR RATINGS
No.
14
115
MOTOR DRIVE
any time of the day the amount of power used. These instruments,
moreover, can be moved from place to place, until every motor in
the shop has been included, thus acquiring valuable data for shop
This is especially valuable immediately after a drive is inrecords.
stalled as a means of ascertaining whether or not a motor of proper
size
and characteristics has been
selected.
Application of Motors to Machine Tools
Considering the application of motors to specific tools, we can
The first class
best divide the problems presented into two classes.
comprises those tools in which the removal of metal is continuous,
The second class contains
such as lathes and drilling machines.
those tools in which the removal of metal is intermittent, as with
and slotters.
For use with machine tools of the first class, variable-speed shunt
motors will be employed, and the next point to be considered is the
planers, shapers
BELT DRIVE
Fig.
1.
Comparison
of Belt
MOTOR DRIVE
Machinery
and Motor Drive of Engine Lathe
speed range for which they must be adapted. For a given horsepower
the size of the motor will be inversely proportional to the minimum
speed, and as the use of gearing or chain drives places a practical
limit on the maximum speed, the minimum speed, and consequently
The best
the size of the motor, will depend upon the speed range.
idea of the actual results that can be obtained with field controlled
motors may be secured from a table showing the outputs and speed
ranges of a standard line of such motors. Although different makes
vary somewhat in their ratings from those given in Table I, this
gives a correct average of the various lines upon the market.
With a wide motor speed range, a larger part of the working
range of the tool is, of course, covered than with a more limited
range, but as it is impracticable to cover the entire working range
of such a tool as a lathe or boring mill by a corresponding motor
range, it is customary to use one or more mechanical speed changes
augment the electrical range. The problem is, therefore, to select
a motor speed range that will give satisfactory results without in-
to
APPLICATION OF MOTORS TO MACHINE TOOLS
15
Actual experience has
elaborate mechanical changes.
under average conditions, a motor speed range of 2% to
1, or 3 to 1, together with two mechanical speed changes, will cover
practically any range of speed that is obtainable with a cone-pulley
drive on any of the ordinary types of machine tools.
To show just how this works out, we will take an actual case of
an engine lathe provided with a five-step cone pulley. In making
too
volving
shown
that,
applications to old lathes it is desirable to retain the back-gearing,
while the cone is removed from the spindle sleeve and two gears
mounted thereon as shown in Pig. 1. The motor is placed above the
headstock, on a bracket, and is geared to an intermediate shaft run-
ning directly below. This shaft carries two gears, A and B, either of
which may be meshed with its corresponding spindle gear E or F.
The engraving shows a comparison of the spindle speeds obtained
with the original belt-drive and those that may be secured by the
Machinery
Fig.
2.
Plate and Brackets for Supporting Motor
application of a 3 to 1 motor. Not only is the range of spindle speeds
increased, but whereas in the belt range of 75 to 580 revolutions we
obtained but five distinct speeds, with the motor and a twenty-step
controller we obtain a range of 75 to 675 revolutions with forty
running speeds, varying by about 6 per cent. This calculation considers only the range of speeds obtained without the backgearing of the lathe and the range is, of course, repeated at correspondingly lower speeds by the introduction of the single or double
different
back-gearing with which the lathe is provided.
Just here it may be well to point out one of the greatest advantages
It will be noticed that the belt drive, which
of the motor drive.
gave a range of 75 to 580 revolutions, did so in five steps varying by
If the lathe is running on, let us say,
at least 60 per cent per step.
the fourth step it may be found that the cutting speed, owing to the
size of the work or the condition of the tool, is not as high as could
To jump to the next speed, however,
be used to best advantage.
increases the cutting speed over 60 per cent, which will be too much,
No.
16
115
MOTOR DRIVE
and the work
will consequently be done on the fourth step, although
be 30 or 40 per cent below that at which the best economy
would obtain. With a motor drive giving speed increments of 6 per
cent or less, the work can at all times be done at practically the best
speed, and the increase of output that will be thus secured will be
this
may
readily appreciated.
Another typical case
shown
where the advantage
of the
motor drive
is
in the facing of a large surface such as a flange.
The ordinary practice is to adjust the speed properly for the cut at
the largest diameter and then cover the entire surface at this speed,
clearly
is
although, as the tool approaches the center, and the cutting diameter
will be too low.
To be sure, an
becomes smaller, the cutting speed
Machinery
Tig.
3.
Motor Equipment
of Horizontal Boring
Machine
shift his belt from time to time as the
progresses, but this is practicable only after a reduction in speed
of the 60 per cent made necessary by the large intervals between
With the motor drive, requiring only the slight
the cone steps.
energetic lathe
hand can
work
movement of the controller handle to adjust the speed, the operator
will continually "notch-up" his controller, so that the entire surface
will be covered at practically maximum speed.
In making
number are
this application to belt-driven lathes, if a considerable
it will be found economical to make a pattern
alike,
and cast a bracket that can be attached neatly to the headstock.
This bracket will be provided with bearings for carrying the intermediate shaft below the motor. As this entails expensive pattern
work,
it
will be cheaper, if the
number
of similar lathes is small,
APPLICATION OF MOTORS TO MACHINE TOOLS
17
No.
18
115
MOTOR DRIVE
wr ought-iron brackets to support a plate on which the motor
can be placed. This plate will require a very simple pattern which
can be readily changed to suit different sizes of motors for various
tools with which it can be employed.
Fig. 2 gives a general idea
of such a bracket, and indicates the method of supporting it over the
headstock of a lathe.
The same scheme works out very satisfactorily for applying motors
to other types of tools, although certain modifications may be needed
in order to obtain the best results. Fig. 3 shows a horizontal boring
machine which has been equipped in a manner similar to that of
the lathe. The cone is replaced by the two gears C and D, but in
to use
Fig.
6.
Motor applied to a Vertical Milling Machine
this case the pinions A and B are fast on the intermediate shaft,
while the gears C and D are free to slide on a feather in the spindle
quill, so as to be engaged at will with their corresponding pinions.
The intermediate shaft, in this case, is carried in brackets in front
of the motor rather than beneath it.
Fig. 4 shows how this type of
drive, with underneath intermediate shaft, may be applied to a
radial drill, and the same arrangement will be found readily applicable
to upright drills.
The halftone Fig. 5 shows the application of a motor drive to a
The arrangement is extremely simple, consisting
large boring mill.
of replacing the driving pulley with a chain sprocket, and driving
APPLICATION OF MOTORS TO MACHINE TOOLS
19
from the motor which is set at any convenient near-by point. The
two pinions for the gear changes are seen in front of the original
driving gears of the mill.
For operating milling machines the most successful applications
The motor may be placed on a floor
are made with chain drives.
base attached to the base of the machine, or it may be bracketed onto
the top of the machine, illustrations of both of these arrangements
being shown in Figs. 6 and 7. The latter motor position is preferable,
as the chips from the machine necessitate the use of a fully enclosed
Fig. 7.
motor
if
it
shown are
is
Motor Equipment of Universal Milling Machine
placed below the table of the machine. The examples
mainly as suggestions, as the construction and
offered
speeds of each particular tool will call for separate consideration.
Horsepower Required
Having decided upon the desirable speed range and the mechanical
details
of
the
application,
followed, as so
many
the next problem
is
the selection of a
this point no positive rules can be
For the
factors enter into the consideration.
motor of suitable power.
Upon
20
No.
115
MOTOR DRIVE
operation of a lathe for general work a 5-horsepower motor might be
fully adequate, while for driving the same size of lathe for manufacturing purposes, and using only high-speed steel at maximum
cutting speeds, a 10- or even a 15-horsepower motor might be needed.
For running a milling machine, for example, it is obvious that a
much
smaller motor could be employed if the machine were to be
used only for finishing work, with light cuts, than would be needed
on the same machine if it were to be used for heavy roughing work.
Any tabulated data, therefore, based on the size of the tool, must
necessarily give averages only, and should be modified by one's best
judgment, based on the actual conditions obtaining.
TABLE
II.
AVERAGE POWER REQUIREMENTS OF ENGINE LATHES
Character of
Swing,
Inches
12
16
18
20
24
Work
Character of
Work
APPLICATION OF MOTORS TO MACHINE TOOLS
21
Application of Motors to Planers, Shapers, etc.
The second class of tools comprises those in which the cutting
stroke alternates with a non-cutting return stroke, as in the case
of planers, shapers and Blotters. Here the successive operations of the
shown in Pig. 8. The highest points in the
As the
those which occur when reversing takes place.
return stroke is taken at two or three times the speed of the cutting
stroke, the power required to accelerate the bed of the planer or the
head of the slotter to its return speed usually constitutes the greatest
power demand, while a somewhat lower point is reached on the
reverse to cut.
It is not, however, necessary to power the tool to
tool occur in cycles, as
cycle
are
TABLE
Swing,
Inches
18
24
36
42
IV.
AVERAGE POWER REQUIREMENTS OF DRILLING MACHINES
Upright,
to
to
iy2 to
2
to
1
1
No.
22
MOTOR DRIVE
115
and often a range
1%
found
such wide
speed ranges as the shunt-wound motors, since any considerable weakening of the shunt field so changes the relation of the shunt to the
series winding as to cause the motor to attain the nature of a series
ficient for nearly all cases
satisfactory.
of
to 1 will be
Compound-wound motors are not used
for
motor, which is undesirable.
In some new planers on the market, pneumatic or magnetic clutches
are used for reversing, but in equipping old tools it will be found
-REVERSE TO RETURN
-REVERSE TO CUT
RETURN
L
CUT
Machinery
Fig.
8.
Cycle of Operations of Planer
A
practicable to retain the cross-belt drive with belt shipper.
diagram of such an application is shown in Fig. 9. The motor is
mounted on the top of the planer housings, and geared to a counter-
more
shaft which carries the driving pulleys. The use of the flywheel on
is most desirable, as it greatly relieves the motor on
the peak loads.
By mounting it on the motor shaft, instead of on
the motor shaft
Fig.
9.
Motor Equipment of a Planer
the slower running countershaft, the flywheel effect is much increased.
It is also well to provide the driving pulleys with extra heavy rims
for the additional flywheel effect that they will produce.
On Blotters
it will usually be found convenient to place the motor on a bracket on
the side of the frame, and employ a gear drive, while shapers may be
either geared or chain-driven, or belt-driven by using an idler as
in Fig. 10.
shown
APPLICATION OF MOTORS TO MACHINE TOOLS
The remarks regarding the power requirements
tools apply
23
for constant-cutting
with equal force to this class of machines.
The
figures in Table VII are based on the use of two tool-heads and
a return speed having a ratio to the cutting speed of about 3 to 1.
If more than two heads are used, or if the planer has a longer bed
than that given, the horsepower should be somewhat increased.
In addition to the motors employed for operating the tools of the
above classes, there are a number of uses for auxiliary motors as will
Fig.
10.
Motor Equipment of Belt-driven Shaper
be noticed in some of the illustrations. In Pig. 3 is shown an auxiliary
motor used for raising and lowering the table of a horizontal boring
machine, while Pigs. 9 and 11 show similar motors employed for
elevating and lowering the cross-rails of a large planer and boring
On large lathes auxiliary motors are often used
mill, respectively.
for moving the tailstock along the bed, and they may also be arranged
for turning the turret heads on heavy turret lathes.
Series motors only are used for these purposes, as they are always
started under full load, and have their speed regulated by armature
No rules can be laid down for the power of these auxiliary
motors, but the requirements are comparatively small, from 2 to 5
control.
horsepower covering all of the above cases except for the very largest
tools.
The time of duty is very short. The drives are invariably by
means of gearing to the operating shaft, one set of reducing gears
frequently being needed to reduce the speed of the motor sufficiently.
These motors should never be belted, for if the load should be thrown
off, by breaking the belt, they will run up to a dangerously high speed,
and may be badly damaged. Another type of auxiliary motor is shown
24
No.
in Fig. 11,
where
large boring mill.
115
MOTOR DRIVE
is used to operate the slotting attachment of a
Such a motor should be compound wound and the
it
data relative to Blotters are applicable for such motors.
TABLE
Width between
VII.
AVERAGE POWER REQUIREMENTS OF PLANERS
APPLICATION OP MOTORS TO MACHINE TOOLS
25
supplied as a separate unit which is connected to the drum by wiring.
The controller should be mounted on the tool at any point to best
suit the convenience of the operator.
In the case of long lathes a
good arrangement is to mount a handle on the lathe apron, and this,
by means of gears and shafts can readily be arranged to operate the
controller when mounted on the end of the lathe bed.
The resistance, if separate, should be mounted near the controller
in order to economize in wiring, but it should be so placed as to be
exposed to the air and at the same time protected from dirt and
Do not cover up the resistance or place it
cuttings from the tool.
inside of the tool frame, but select some place above the table of the
tool, away from the path of the chips.
Methods of Applying Motors to Machine Tools
In a paper on the Economy of the Electric Drive in the Machine
Shop, read at the April, 1910, meeting of the American Society of
Mechanical Engineers, Mr. A. L. De Leeuw reviewed the conditions
which must be considered in connection with the equipment of a
machine shop with electric drive. In conclusion he gave a general
idea of the mode of application of motors to machine tools, the selection of motors for different classes of tools, and the lines along which
economical results may be expected. The following abstract of these
conclusions will undoubtedly be of interest to mechanics in general.
Bench and Speed Lathes
Bench lathes should be driven from a countershaft attached to the
wall or bench and driven in turn by a motor.
Any kind of motor
The
except a series-wound or heavily compounded motor will do.
object of the motor drive is to get the machine in the best possible
location without regard to the location of the lineshafting. A number
of these machines may be driven by a common lineshaft, which in
driven by a motor.
Speed lathes should be driven from a countershaft located under the
In the latter case a variablelathe, or by a direct-connected motor.
speed motor is to be preferred, if direct current is available. Motor
drive is recommended when the machine is used in the assembling department, as the machines may then be placed where they are most
needed; the crane service would also interfere with countershafts.
There will be no material gain, if the machines are to be used for ordifrurn is
nary shop operations.
Engine Lathes
Various methods of driving engine lathes by motors are in use. Some
makers furnish motor-driven engine lathes as standard equipment.
Some have a headstock with a limited number of speeds, and depend
on a variable-speed motor to fill out the speeds of the lathe. Others
apply a constant-speed motor, or one with a limited amount of variatIn general, the use to which this
ion, to an all-geared headstock.
class of machines is put in the shop would naturally lead to group
No.
26
115
MOTOR DRIVE
There is no material advantage in the individual motor drive,
the machines are used for regular manufacturing operations, except
where the location demands individual drive.
drive.
if
Heavy Engine
Heavy engine
a
lathes,
direct-connected
Lathes, Forg-e Lathes, Etc.
and lathes
motor.
of similar types should be driven
The motor should be
by
direct-current,
as
these machines are too heavy to permit a convenient all-gear drive.
no direct current is available and there is only one machine of
its
If
and this is used for an occasional job only, an alternating-current motor could be used, leaving a wide gap in the speeds.
If these machines are used for manufacturing purposes, it would pay to
install a small synchronous connector.
The speed range in the motor
class in the shop,
does not need to exceed two to one, though a wider range
is
better
if
obtainable without complications or great expense. The position of
the motor should be low, as the vibrations in the motor-support have a
decided influence on the capacity of the machine, as well as on the rebill.
The output of this class of machines may easily be increased
from 20 to 25 per cent by motor drive. Further advantages of the
motor drive are the possibility of placing the machine in the line of
the routing of heavy work, and of placing it immediately under the
pair
be reached with a belt-driven
gallery, if the construction of the shop lends itself to this arrangement, but the same convenience as that of the motor drive cannot be obtained.
traveling crane.
This latter object
may
machine by placing the headstock under the
Axle and Wheel Lathes
the greatest importance that axle lathes and car and driving
wheel lathes should have the highest possible efficiency, and the most
It is of
These machines are mostly used in locomotive
and car repair shops, where time saved does not mean merely the
saving of wages, but each day gained means an added day in the
convenient location.
earning capacity of the engine or car. It is, therefore, important that
these machines be motor-driven whenever installed in a railroad
repair shop, though this does not mean that they should not be so
driven if used for manufacturing.
Direct current should be used.
The economy of the motor drive should not be figured in increased
output, but in reduction of time required to repair an engine or car.
Chucking Lathes
Generally speaking, there is little reason why a chucking lathe
should be motor-driven. Most chucking lathes are provided with the
necessary mechanism to shift speeds quickly. A few types handling
large work may be motor-driven to advantage, though practically
the only advantage lies in the fact that small gradations in speed
can be thus obtained. Such machines, therefore, require a variablespeed motor.
Automatic Screw Machines
Small automatic screw machines are generally group-driven. Large
machines may be individually motor-driven to good advantage. The
APPLICATION OP MOTORS TO MACHINE TOOLS
27
larger sizes have generally one or two speeds for one piece of work,
though these speeds may be varied when the machine is reset for a
new piece of work. The speed given to the machine must naturally
be proportional to the largest diameter to be turned, or in other
This will reduce the speed for
words, to the size of stock used.
some of the operations, such as drilling and reaming, far below the
economical speed. The amount of time saved by the application of
the variable-speed motor may be considerable. Where the construction
of the machine permits, two motors, one for feed and one for speed,
would give still better results. In all cases variable-speed motors
should be used.
Drill
Presses and Boringr Machines
The only reason why the sensitive drill should be individually
motor-driven is that it is often usec in an assembling department,
where height of ceiling and crane service would make a belt drive
1
.
awkward
Most sensitive drills have, in themselves,
or impossible.
the speeds required for their work, so that any type of motor
The motor may either be directly applied to the
will be adaptable.
machine or may drive a countershaft on a stand; or it may be placed
on the floor by the side of the machine, in case the machine carries
its own set of cones or other variable-speed device.
Generally speaking, the upright drill is used for manufacturing
There
operations and does not require frequent changes of speed.
are, however, many exceptions, for instance, where upright drills are
used to do all the operations on a piece by means of a jig. In this
all
case frequent changes of tools, and, therefore, of speeds, are required,
and an individual motor drive, whether direct-connected to the ma-
chine or operating on the countershaft, is of the greatest benefit. No
great benefit can be derived from a constant-speed motor with this
Radial 'drills may be considered to present the
type of machine.
same requirements as upright drills. There is an additional reason
why radial drills should be motor-driven they are often used in the
neighborhood of the assembling floor.
When the work for boring machines is specialized and the machines
perform only one operation, there is no good reason why motor drive
should be preferred to belt drive. Where, however, the machine is
used for a multiplicity of operations, such as drilling, boring, reaming
and facing, a motor drive is beneficial if a variable-speed motor is
used. The range of speed of the motor should be as wide as possible,
so that no gears may have to be shifted for the entire set of operations
on a single hole. Especially where a boring machine is used for facing, this variable speed will be found highly economical.
Grinders
Grinders, in general, require so many various movements driven from
countershafts that it is hardly possible to apply a single motor directly
to the machine; the best that can be done is to attach the countershaft to the machine and drive the former from a motor standing on
No.
28
115
MOTOR DRIVE
the floor or on a bracket attached to the machine. In isolated cases
would be well to have one or more motors, each controlling a single
it
operation, attached directly to the machine.
Planers, Shapers, Blotters
Planers in general are not benefited by the application of a motor,
the motor only complicates the difficulties of a planer drive.
However, large planers which must be placed under a crane give
better results when motor-driven on account of the facility of handling
the work.
Another possible advantage when using a variable-speed
motor and controlling the speed of the motor at the end of the stroke
is that much higher return speeds can be obtained in connection
with any desired cutting speed. What is true of planers is also true
of shapers and slotters.
Local conditions may make it advisable to
drive them individually by motor, but generally speaking, there are
no great advantages to be gained with this drive.
as
Milling Machines
The larger
sizes of
knee-and-column type machines,
will give the best results
if
the motor
if
motor-driven,
of the variable-speed type,
are used for gang work.
This is
is
especially where these machines
due to the fact that the speed of the mills is dependent on the largest
cutter in the gang, while the feed is dependent on the smallest cutter,
not counting the limitations due to the nature of the work. It is therefore important that the speed should be as close to the permissible
limit as possible.
When
applied to this type of milling machine, the
motor should be as low down as possible, as vibrations in the machine
have a marked effect on the quality of the finish. In practically all
cases the planer type of milling machine should be motor-driven, in
order that it may be located under a crane. It is not so very important, however, whether the motor is of the constant-speed or variablespeed type.
Punches, Bending- Bolls, Shears, etc.
This class of machinery, used largely for boiler, bridge, structural
iron and ship-building work, is generally placed in high shops and
under cranes, and in locations and directions most convenient for
the routing of the work. The shops in which it is placed are generally
large and contain a relatively small amount of machinery, so that the
amount of transmission gearing required is large in proportion to the
amount of machinery. It is for this reason advisable in almost all
cases to drive this class of machinery by an electric motor, which, of
course, does not need to be of the variable-speed type.
CHAPTER
II
WIRING ON MOTOR-DRIVEN MACHINERY
Electrical wiring on the motor-driven machines furnished by even
the best manufacturers is too often poorly arranged and inefficiently
installed.
This is because the wiring is not considered when the
is designed.
Its installation is usually left to some workman
does the best he can. The wiring and arrangement of the control
apparatus should be laid out in the drafting-room. This chapter discusses the best methods of machine wiring, describes the materials
used, and gives concrete directions, rules and tables for wiring motordriven machinery.
One industrial corporation which purchases many motor-driven machines incorporates the following clauses in the specifications for all
such equipments:
machine
who
1.
The machine manufacturer
shall
mount the motor and
ling devices on the machine so that they shall
and shall wire between them as hereinafter noted.
control-
form a part thereof,
The controlling apparatus shall be conveniently arranged for
2.
manipulation by the machine operator.
All wiring shall be installed in accordance with the regulations
3.
of the National Electrical Code^
All wiring shall be carried in wrought-iron conduit or in metal
4.
conduit fittings. These shall be firmly attached to the frame of the
machine.
5.
So far as possible, all "live" bare metal parts shall be enclosed
with metal covers.
It was found desirable to makes these requirements because of the
awkward
practice prevailing in this respect among machine builders.
the builder of the motor-driven machine, although he
Frequently,
mounted the motor and arranged the drive between the machine and the motor, would fail to mount the motor-starter or conIf he did mount it on the machine, in the
troller on the machine.
great majority of cases he would either provide no wiring between
the motor and the controller, or install the wiring in such a careless, unbusinesslike manner that it would have to be reinstalled.
Usually, the machine builder makes an extra charge for arranging the
wiring in accordance with the above specifications; but it was found
that the work was done better and more cheaply by the builder than
carefully
by the wire-men at the plants where the machines were installed.
At the present time, when motor-driven machinery is so generally used,
machine builders are paying more attention to the electrical details;
but there
some
much to be desired. In the following will be given
information that may be of value to manufacturers
is still
practical
30
No.
115
MOTOR DRIVE
desiring to arrange and install the wiring on their machines as efIt is believed that good wiring will be appreficiently as possible.
ciated by the purchaser.
Rule No. 1 in the specifications given states that when the machine
direct-driven the motor and controller should be considered as a
Obviously, they are just as much so as is a
part of the machine.
If possible, the complete equipment should be shipped so that,
gear.
after setting up, it will only be necessary for the plant electrician to
is
run a pair of wires to put the machine in service. For large machines,
which must be dismantled for transportation, the motor and controlling equipment must be shipped separately, and it may be necessary
to dismount the conduit carrying the electrical conductors; but if the
wiring has been properly connected and the conduit strapped to the
machine in the erecting shop, it can easily be reinstalled. Thus, cranes,
which have complicated wiring, can be taken apart, shipped, reerected and rewired with very little difficulty.
The desirability of the requirements of Rule No. 2 is so obvious as
to need no discussion.
Rule No. 3 requires that all wiring be installed in accordance with
National Electrical Code regulations. Standard fire insurance policies
require that the electrical work in all plants having insurance proIt has
tection be installed in accordance with these regulations.
taken many years to mold the regulations into their present excellent
form, and they are revised constantly to keep abreast with the advances in the art. It is therefore essential that machines which are
to be installed in plants carrying fire insurance, be wired in accordance with the Code. Even if insurance is not carried, it is advisable
to follow these rules, as they outline a substantial and safe method
A copy of The National Electrical Code will be supplied
of wiring.
free to any one making request to the local Fire Underwriters' Inspection Bureau or to the Underwriters' Laboratories, Chicago, 111.
Rule No. 4 requires that wiring be installed in wrought-iron conduits
or in metal conduit fittings.
It costs several times as much to run
wiring in metal conduit (the properties of conduit are given in Table
XII) as to arrange it without mechanical protection. However, it is
only the first cost of conduit wiring that is high. When placed in
conduit the wiring is done once for all; there is no future trouble
from broken wires, grounds or short circuits, due to abraded insulation.
When arranged with conduit wiring, the machine is easier
to keep clean and looks neater.
The conduit fittings (which will be
described later) are used at points where wires issue from the conduit
or where a turn in the conduit run is necessary and it is not desired
to bend the conduit. In general construction, they somewhat resemble
screwed pipe fittings, but they are always arranged with removable
covers so that the wire is easily accessible. Conduit and fittings are
attached to machine frames with either pipe straps (Table XV) or
machine screws, as will be described.
Rule No. 5 requires that all "live" bare metal parts be enclosed
within metal covers.
It is usually feasible to enclose "these parts.
WIRING ON MOTOR-DRIVEN MACHINERY
31
Such enclosure prevents metallic chips from forming grounds or short
and renders shock to attendants impossible. With the voltages
at which machine motors are usually operated, a shock is not often
fatal, but one hears of cases where men have been killed from contact
with 220-volt circuits. At any rate, an electrical shock is unpleasant, and if there is a possibility of receiving one the attendant is
likely to be cautious and waste time. Fire risk is reduced by enclosing "live" parts. Although the Underwriters do not require enclosure
The electrical manufacturers appreciate the dethey commend it.
mand for enclosed apparatus, and it is now possible to buy standard
starters and controllers, for nearly all applications, that are well protected and so arranged that conduit wiring can be readily installed.
circuits
Wire for Motor Application
wire to use for transmitting electrical energy (in lowvoltage work such as that involved in industrial-plant wiring) is
determined by two requirements, viz., the cross-sectional area must be
large enough to carry the current required without getting too hot,
but must not be so large as to cause an excessive drop in voltage
The
size of
However, the dispressure and consequent energy loss.
tances involved in wiring machinery are so short that the latter requirement may be disregarded altogether. The only demand is, then,
that the wire be big enough to obviate excessive heating.
electrical
The National Electrical Code specifies that all concealed wires shall
be rubber-insulated and, in addition, that all wires carried in conduit
All standard rubber-covered wires
shall have a double-braid covering.
used for voltages above 10 and below 600 have the same thickness of
insulation.
Copper wire is almost universally used for interior wirTherefore, if the voltage of the motor is below 600, wire for the
ing.
installation should be specified, for example, thus:
No. 6 National
Code Standard, 0-600 volts, double-braid, stranded, copper
size of wire, and whether it is to be solid or stranded, is
determined, as will be explained, by the horsepower output of the
Electrical
wire.
The
motor.
So that wire in service will not be dangerously overheated, the
Underwriters have specified a certain safe current-carrying capacity
for each size of wire and for wires having different insulating maIn Table
are given the safe current-carrying capacities for
terials.
all sizes of rubber-covered wire that the machine builder is likely to
use.
The sizes listed are all commercial ones and are, as a rule,
readily obtainable. When the current or amperes taken by any motor
is known, the size of wire to be used can be ascertained from Table X.
Although Nos. 18 and 16 wires are listed in the table, the Underwriters do not permit the use, for applications such as herein treated,
of any wire smaller than No. 14.
It will be noted that the wires
between No. 18 and No. 8, inclusive, are tabulated as "solid" and those
Solid wire is that having a solid
larger than No. 8 as "stranded."
conductor, while the conductor in stranded wires is twisted up from
several or many wires of relatively small diameter.
Stranded wires
are sometimes called cables. It is the usual practice in conduit work
X
No.
32
115
MOTOR DRIVE
to specify that wires larger than No. 8 be stranded, because, if solid,
they are too stiff to be handled and pulled into the conduit readily.
Solid wires can be obtained, if desired, in sizes much larger than No.
8 and these are much used in "open-work" wiring.
The numbers of
wires in a strand given represent the practice of some manufacturers,
but other manufacturers have different standards. They vary little,
however, from those shown. As a rule, it is not desirable to specify
the "number of wires in strand" when ordering, as the dealer may
TABLE
X.
SPECIFICATIONS FOR WIRE AND CONDUIT ON
MOTOR-DRIVEN MACHINERY
Double-braid, Rubber-covered, to 600 Volts, N. E. C. S. Copper Wire,
N. E. C. S. Wrought-iron Conduit
WIRING ON MOTOR-DRIVEN MACHINERY
are averages and may vary somewhat from name-plate ratings. Different makes of motors of the same horsepower have different ef-
with alternating-current motors,
and both these appreciably affect the amount
ficiencies and,
figures given in Table
XI
different power factors,
of current taken.
The
indicate the current in each wire.
That
is,
they show the number of amperes flowing through each of the two
wires to a direct-current or to a single-phase alternating-current
motor, through each of the four wires to a two-phase alternatingcurrent motor, or through each of the three wires to a three-phase
alternating-current motor.
Having found the current, in amperes, taken by a motor, the size
of wire to be used cannot be selected without first considering another
TABLE
Motor
of
H.P.
XI.
APPROXIMATE FULL-LOAD CURRENT
TAKEN BY ELECTRIC MOTORS
(IN
AMPERES)
No.
34
115
MOTOR DRIVE
about 25 amperes when operating at full load. To allow for a 25
per cent excess current, in accordance with the Code rule, an estimate
is made thus:
31 amperes (about).
25X1.25
Referring to Table
X, a No. 8 (solid) wire which has a safe carrying capacity of 33
amperes is the smallest that can be used.
=
The insulation on rubber-covered wire deteriorates very rapidly
under the action of heat, so if it is necessary to install conductors
where they will be subjected to high temperatures, wire having "slowburning" insulation should be used. Such wire, if enclosed, must be
(according to the Code) in "lined" conduit. This conduit is described
under the following heading.
Conduit for Motor Application Wiring
Wrought-iron conduit is merely standard-weight steel, or possibly
in some cases wrought-iron pipe, which has been thoroughly cleaned
to remove burrs and scale, and then either enameled or coated with
zinc.
Conduit which meets the requirements of the National Electrical
Code and which has been approved by an Underwriters' inspector,
is called National Electrical Code standard conduit or N. E. C. S.
In Table XII are given the principal dimensions of comconduit.
mercial N. E. C. S. conduit, elbows and couplings. Conduit is furnished only in lengths of ten feet.
Electrical conduit is threaded
with standard pipe threads and standard-weight screwed pipe fittings
will
fit it.
In addition to the "unlined" conduit, described above, a "lined"
conduit is manufactured which has a relatively thick insulating lining.
The lined conduit is seldom used as it is more expensive than the unlined and the latter has given entire satisfaction. The insulating
lining appears to be unnecessary, as the rubber insulation on standard wire provides excellent protection.
Although its use would be prohibited by the Underwriters, there
is really no objection to using commercial wrought-iron pipe instead
of conduit for wiring machines. Such pipe should be carefully cleaned
inside and out and every precaution taken to make sure that there
are no burrs or slivers on the inside of the pipe which might cut
insulation on wires. After the pipe is painted, it is almost impossible
to distinguish it
from conduit.
Conduit elbows are formed from conduit to the dimensions indicated
in Table XII.
The smaller sizes of conduit can be bent cold to any
desired contour, but it requires some skill to do the bending. Conduitbending machines are obtainable and their installation pays if there
Both power- and hand-operated types are
is much wiring to be done.
manufactured. Couplings for conduit are exactly the same as screwed
couplings for standard-weight pipe, except that the former are either
enameled or coated with zinc and have a better finish.
After determining the proper size of wire to use for supplying
energy to a given motor, the size of conduit to carry it can be selected
from Table X. The sizes theretabulated, for the different sizes of
wire, have been chosen as the result of much experience with conduit
wiring.
They are
sufficiently large to allow wires to be
drawn
in or
WIRING ON MOTOR-DRIVEN MACHINERY
35
S5
o
M
O
.2
1
I' "!
?*
s-g
m RS
^s
bccs
a
O
If 8
T-<
TH OJ'OJ CO iC t- OS
O
i!
si
1?3
2s
5
tS
I*
<
G^'^oOr-<CDOCO'TC<}
OOOCOCOO^OiCO
II
s
10
10 1O
OCO5OO5CCOOOOtO
.I'o!*'*c
;w
S5
No.
36
MOTOR DRIVE
115
out without the application of excessive force. It is a common error
to choose a conduit size so small that the wires must be pulled in
with blocks 'and tackle. If this is done, the insulation
be injured and withdrawal may be impossible.
is likely to
Conduit Fittings and Sundries
Where wires emerge from conduit ends, the Code requires that provision be made so that a possible burr on the inside of the conduit
will not abrade the insulation on the wires when they are being drawn
TABLE
Thomas and
XIII.
DIMENSIONS OF CONDUIT BUSHINGS
All Dimensions taken from Samples.
Dimensions in Inches
Betts Bushings.
All
Size of
Conduit
H*
Uf
2U
in or out.
as
Conduit ends
may
be protected either by a bushing, such
shown
in the engraving accompanying Table XIII, or by a fitting,
of one of the types shown in Fig. 14, equipped with a porcelain cover,
The bushing should be used when the conduit terminates
Pig. 12.
within an enclosed outlet, junction, or panel box (see Pig. 13) which
may be made of either cast or sheet iron. The dimensions given in
Table XIII will prove useful in indicating what clearances are required
for screwing the bushing on the end of the conduit and will also
assist in determining the locations for the conduit holes.
Outlet boxes usually have unthreaded holes for the conduit, as
indicated in Pig. 13, but where a waterproof installation is essential,
WIRING ON MOTOR-DRIVEN MACHINERY
TABLE XIV. DIMENSIONS OF CONDUIT LOCK-NUTS
-H T kMachtnery.N.Y.
Thomas and
Betts Lock-nuts.
All
Size
of
Conduit
All Dimensions taken from Samples.
Dimensions
in
Inches
37
No.
38
115
MOTOR DRIVE
When the holes are unthreaded, a locknut (shown with Table XIV) is run on the end of the conduit and,
after the bushing is screwed to position, the lock-nut is turned up
snugly against the side of the box, binding the conduit firmly in
position. It should be understood that the dimensions given in Tables
XIII and XIV for bushings and lock-nuts are accurate for only one
manufacturer's line. There are several different makes available, but
all will measure approximately the same as those shown.
the holes should be threaded.
The application of
conduit fittings can
best be shown by an
In Pig. 15
example.
is illustrated a motor-
driven open-side
planer with the wirbetween the
ing
starter and the motor
neatly carried in conAt the motor
duit.
terminal
the
con-
ductors issue through
a
fitting,
which
is
of
the type shown in Pig.
14 at C, equipped with
the cover shown in
Fig. 12 at B.
FRAME OF MACHINE
PLAN VIEW
The
con-
are
so
duit
fittings
made
that any style of
cover of a given pipe
size will
iron
,
sponding
SCREW HOLDING BOX
TO MACHINE
any
fit
cast-
of
corre-
pipe
size.
fitting
The covers are held on
with brass screws.
17
Fig.
is
arrangement
SECTION A-A
Fig.
13.
Outlet
Xachtnerv.y.Y.
Box Mounted on Machine
In
shown an
of
fit-
tings
that
might be
used
with
the
of
starting
type
panel
shown in Fig. 15, if the motor were located below instead of above
It will be noted that where "elbow" fittings (G and H,
the panel.
Fig. 14) are arranged with metal covers, they are effectively used at
turns in the conduit run, instead of bends or wrought-iron elbows.
Fig.
A
18 illustrates further applications of conduit-fitting elbows.
very convenient feature of the fittings shown in Fig. 14 is the
By means of this
provision of a headless set-screw in the throat.
set-screw it is possible to secure a conduit end firmly in a fitting
even if the threading on the conduit is faulty or if, because of a
WIRING ON MOTOR-DRIVEN MACHINERY
39
does not set up tightly in the fitting, when
In this type of fitting, conduit can be secured
The set-screw provides ample atwithout being threaded at all.
tachment, if conduit and fittings are firmly fastened to a supporting
Nor is it necessary to
surface, as they usually are on machinery.
An unthread conduit running into fittings like that in Fig. 16.
threaded end of a conduit length is inserted in the nipple, the nut is
The threaded portion of the
tightened, and the conduit is secured.
bend in the conduit,
it
in its proper position.
nipple
and tapered. These fittings possess several advantageous
Being of sheet-steel, they are unbreakable. The fact that
is split
points.
Fig.
14.
Types of Cast-iron Conduit Fittings
each fitting has several "knock-out" holes makes possible a great
of combinations from a comparatively small stock of fittings
number
and covers.
Supporting Conduit Wiring
Obviously, conduit carrying conductors should be so securely supported that there can be no chance of its being displaced under reasonable conditions.
Pipe straps, formed from sheet-steel and then gal-
shown with Table XV, are most frequently used
and 18. The dimenXV
making clearance al-
vanized, such as those
for supporting conduit, as shown in Pigs. 15, 17
sions given in Table
will be found useful in
lowances and in determining the locations for the tapped holes for the
round headed machine screws, with which the straps are fastened.
The dimensions in Table XV are accurate only for the lines of certain
manufacturers, but will be approximately correct for all makes.
Another good method of supporting conduit runs is by fastening
the fitting to the machine frame with machine screws, as shown in
Figs. 13 and 19. The screws pass through a hole drilled in the bottom
of the fitting and down into a hole tapped in the machine frame.
No.
40
115
MOTOR DRIVE
DRIVEN PULLEY
MOTOR
STARTING
PANEL
CONDUIT
FITTING
Machinery.}?.?.
Fig.
15.
Open-side Planer with Well-arranged Wiring
KNOCK-OUT"
,
PRESSED STEEL BOX
HOLE6
SCREW FOR
I
\
HOLDING
ON COVER
4
HOULDER
>NDUIT
EXPANSION SLOT
END OF
HEADED OVER
SIDE ELEVATION
Fig.
16.
SECTION A-A
FRONT ELEVATION
Machinery, N. Y.
Details of Typical Pressed-steel Fitting
WIRING ON MOTOR-DRIVEN MACHINERY
41
support a complete conduit installation by this
avoid the use of pipe straps.
This
sort of a job presents a neat appearance.
It is often feasible to
method and thereby
entirely
Motors Arranged
When
for
Conduit Wiring-
that the "motor shall be arranged for conduit
motor manufacturers will provide, without extra
charge, a metal ter-
it is specified
certain
wiring,"
.
minal box, with a removable cover, around
the motor terminals.
A motor so arranged
CONDUCTORS FROM
SOURCE OF SUPPLY
shown in Fig. 18.
Such a terminal box
is
NOTE:
permits
FUSES ARE NOT
ORDINARILY REQUIRED
ON A PANEL TO BE
MOUNTED ON A
of
possible
and through
MACHINE
the
best
installation,
its
pres-
ence a conduit
fitting,
like that at the
motor
in Pig. 15, can be dispensed with. A hole
is
provided in the
minal
FRAME
OF MACHINE
box
and
ter-
the
conduit is terminated
with a bushing in the
hole.
Switches
It is
required by the
National
Machinery,N.TT.
Fig.
17.
A
Neatly Wired Starting Panel
Electrical
Code that every motor
and starting box be
CONDUCTOR3
TO MOTOR
protected by a doublepole cut . out (f uses or
and controlled by an indicating switch that plainly
indicates whether the circuit is open or closed. For motors exceeding
in capacity
horsepower, a double-pole switch is required, but a
circuit breaker)
%
may be used for smaller ones. It is always advishowever, to use the double-pole type, as through its use both
sides of a circuit are rendered dead when tha switch is open.
single-pole switch
able,
For handling currents up to 20 amperes, or thereabout, the best
switch to use is of the indicating-snap type, shown in Fig. 20. This
type can readily be obtained as either single-pole, for direct-current
and single-phase alternating-current motors, or
triple-pole for threeAll "live" parts are effectively enclosed in a formed
sheet-metal cover (Fig. 20) which is lined with an insulating material.
phase motors.
By unscrewing
the composition handle, the cover can be quickly re-
No.
42
moved
for
115
MOTOR DRIVE
making connections.
Wires
enter
switch
the
through
holes in the back of the porcelain base. A revolving dial, bearing the
legends "On" and "Off," indicates whether the switch is open or
closed.
An
in
indicating-snap switch mounted on a conduit fitting as shown
All
21 makes a rugged and safe switching combination.
Fig.
wires
and
turers
make conduit
"live"
parts
are
Some manufaccompletely enclosed.
designed for carrying switches;
fittings especially
TABLE XV. DIMENSIONS OF PIPE STRAPS
All
Dimensions taken from Samples.
All
Dimensions
in
Inches
i
i
il
f
I!
No.
2
2*
0.20
0.20
0.20
0.22
0.22
0.22
0.22
0.22
0.25
in.
8X
8X
8x
10X
10X
if
.it
I?
a-c
| $0.40
\
0.45
0.50
0.75
10X1
10x1
ioxu
To
72
40
29
21
18
14
12
2.75
but an equivalent fitting may be assembled, as shown in Fig. 14 at K,
with the components A and J, or with J and any other piece shown in
Fig. 14.
For handling currents above 20 amperes, open-knife switches are
used. The open type is used because (so far as the writer
These
is aware) no enclosed knife switch is regularly manufactured.
open switches are best mounted close to the motor starter. Controllers and starters, as will be outlined later, can be purchased with
the line switches mounted directly on them, as indicated in Figs. 15
and 17. Such combinations are called starting or controlling panels.
commonly
WIRING ON MOTOR-DRIVEN MACHINERY
43
these examples of knife-line-switch and controller applications, it was evidently deemed unnecessary by the designer to enclose
the switches and controllers. If enclosure is desirable (and as many
In
view
all of
there are few cases where
it,
it
is
not)
a cover for a
PIPE STRAP--'
CONDUIT FITTING
WROUGHT-IRON CONDUIT
CONTAINING CONDUCTORS
TO MOTOR
SOURCE OF SUPPLY
Machinery,??.
Fig.
18.
knit'e-
Y
Machine Equipped with Drum Controller
switch can readily be constructed from sheet or cast metal as suggested in Fig. 22. As will be described subsequently, circuit-breakers
are often used on motor-driven machines, making switches unnecessary.
While a cut-out
is
required by the Code to protect every motorit is not advisable to mount this on the ma-
controller combination,
.
/
WROUGHT
SCREWS FOR
FASTENING
IRON
WROUGHT
\ CONDUIT
HOLE DRILLED
BY WIRE-MAN
Fig.
chine.
As a
circuit to the
at
A
in
Fig.
IRON
CONDUIT
19.
,N. Y.
Satisfactory Method of Supporting Fittings
is best located at the point where the branchmachine taps from the main supply circuit, as shown
23.
Hence the machine manufacturer should not be
rule,
it
expected to provide a cut-out.
A
cut-out is ordinarily required at A.
44
No.
115
MOTOR DRIVE
inasmuch as the branch wires are usually smaller than the main
wires and the Code requires the installation of a cut-out wherever
there is a decrease in wire size.
INDICATOR WINDOW
PORCELAIN
BASE
FORMED METAL COVER'
\ PO RCELAIN BASE
FORMED METAL COVER
SIDE ELEVATION
PLAN VIEW
Machinery.*.
Fig.
20.
Y.
Indicating Snap Switch
Motor Controllers and Starters
Motor starters as regularly furnished by the motor manufacturers
are of the open type shown in line-cut Fig. 15.
By "open type" is
WROUGHT-IRON CONDUIT
ENCLOSING COVER
CONDUIT FITTING
CONDUIT CARRYING
CONDUCTORS TO MOTOR
MOTOR
GAUZE
ENCLOSING
COVERS
THIS CONDUIT TO BE
INSTALLED BY PURCHASER
ENCLOSING CASE
FOR CHAIN DRIVE
* A^
Machinery. X.Y.
Fig.
21.
A
Motor-driven Shaper with Completely Enclosed Wiring
"live" parts protected
by a
These open starters have given and will give entire
satis-
meant a type which does not have
cover.
its
WIRING ON MOTOR-DRIVEN MACHINERY
45
faction in places where it is reasonably clean.
But some purchasing
concerns orefer to have, in so far as possible, all electrical apparatus
enclosed, and it is believed that, all things considered, this is usually
the most economical method, although the first cost of enclosed equipment is a trifle higher. An enclosed starter is shown in Fig. 21. It
consists merely of a standard open starter fitted with a cover which
encloses all "live" parts, and has a semi-circular slot for the operating
Most of the electrical manufacturing concerns have standhandle.
ardized and are prepared to furnish enclosing covers for their control
equipment. Such a cover makes it difficult for the unauthorized to
Fig.
22.
Enclosing Cover for Knife-switch
tamper with the adjustment of the starter, keeps it clean, eliminates
liability to shock and prevents grounds or short circuits due to flying
metal chips.
The purchaser of an enclosing cover for a starter should insist that
it enclose not only the dial-contacts, but also the terminals on the
starter.
Certain manufacturers will furnish a cover that will shroud
the dial and not the terminals, unless specifically directed as above;
all bare current-carrying parts should be enclosed.
In Fig. 24 is detailed an excellent enclosing cover that can be apInstead of being slotted for the operating
plied to standard starters.
handle as is the one shown in Fig. 21, a better construction is used.
An auxiliary operating handle and arm is mounted on the cover; on
the end of this arm is an insulating fork which engages the controller
arm when the cover is in its normal position, and thus transmits the
movements of the operating handle to the controller arm. The absence
of a slot in the cover makes the starter dust-proof.
The terminals
are completely enclosed and a removable piece that can be taken out
altogether, for the admittance of wires, or drilled for conduit, is pro-
No.
46
115
MOTOR DRIVE
vided above the terminals. When this cover is applied to the standard controller the old controller handle is removed.
Sometimes a circuit-breaker is substituted for the switch on a
A circuit-breaker is one type
starting panel, as shown in Pig. 25.
of cut-out.
It opens a circuit automatically when a current, of a
value for which it is set, flows through it.
It can also be opened
manually by releasing a catch. Circuit-breakers, of reliable types, are
considerably higher in first cost than a switch-fuse combination, but
in the long run they are more economical. The reasons for this are:
First, fuse renewals, which are relatively expensive, are not required;
and second, the cost of labor wasted while fuses are being replaced,
is
saved.
The panel
construction
in Fig. 25 is shown without enclosing covers so that its
will be apparent; but it is made with covers which
expose only the circuit-breaker and starting-rheostat operating handles.
'
ENTRANCE SWITCH
AND CUT-OUT
At!
MAIN SUPPLY CIRCUIT
BRANCH CUT-OUT
PROTECTING
.MACHINE MOTOR
I
BRANCH CIRCUIT
TO MACHINE
LINE SWITCH
-
STARTER
ED
j
Machinery.N.T.
Fig.
23.
Some manufacturers
Wiring Diagram for Motor-driven Machines
enclose panels like that of Fig. 25 in sheet-metal
boxes having hinged doors, but this is not a satisfactory arrangement for machinery applications, because, to operate the starter
This
or manipulate the switch, the attendant must open the door.
is awkward and, in case of accidents, when the motor should be stopped
The consequence is that the
without delay, prevents quick action.
door is usually left open or is taken off altogether.
As previously mentioned, motors on machines are frequently protected by branch-fuses located at the supply circuit as shown at A
in Fig. 23, and a circuit-breaker or a starting panel provides additional
However, the circuit-breaker should be set to trip on a
protection.
smaller current than will rupture the fuses. The circuit-breaker takes
the brunt of an overload and operates instantaneously, saving the cost
of fuse renewals. As the economies of circuit-breaker applications are
becoming better understood they are becoming more popular. Some
steel
WIRING ON MOTOR-DRIVEN,
large industrial corporations specify
them on every motor
starting or
controlling panel.
Drum controllers with external resistances are deservedly becoming
In Fig. 18 is
very popular, particularly for variable-speed control.
shown drum-controller applications. The drum controller receives its
name from the fact that contact is made between stationary fingers
and rotating segments mounted on a drum. All the parts can be
made very rugged and can be so arranged as to be readily removable
The resistance is arranged in a separate
for renewal and repair.
frame which can be provided with an enclosing cover and arranged
for conduit wiring as shown in Pig.
only the contact-making mechanism.
18.
The drum usually contains
It is believed
that a
drum
con-
SUPPORTING LUGS
.!
DETAIL OF
INSULATING FORK
FORKED PIECE OF
INSULATING FIBER
ENGAGING CONTROLLER
HANDLE
iNTROLLER ARM
WITH HANDLE REMOVED
u
SECTIONAL
FRONT ELEVATION
SIDE ELEVATION
Machinery, N.Y.
Tig.
24.
A
Good Enclosing Cover Design
way to one of the dial type, which has
contact buttons arranged on the face of an insulating panel and a
swinging arm to make electrical contact with them.
Often the drum controller is mounted conveniently near the motor
troller is preferable in every
at the
head of the
lathe.
The
controlling handle, whereby the lathe
started, stopped, or has its speed varied, is attached to and travels
with the apron, and hence is always handily located for operation.
is
The handle engages with a longitudinally
when
slotted shaft so arranged
The shaft extends
nearly the entire length of the lathe and motion is transmitted from
it to the controller drum by means of sprockets and a chain.
It will
be noted that the cover of the drum controller can be easily removed
that
the handle
is
turned the shaft turns.
by unscrewing a couple of swing nuts.
'
48
*
'
'
'
N'oV 115
MOTOR DRIVE
Enclosing Motors
1
Motors can be furnished either open, semi-enclosed or fully enclosed.
fully enclosed motor of a given horsepower and speed costs more
than a semi-enclosed or an open one, because a large frame is needed
for the enclosed type. The power capacity of a motor depends largely
on its ability to dissipate the heat generated within it, and if it is
enclosed, the heat is dissipated with difficulty. To reduce the quantity
of heat generated, the parts must be proportioned more generously;
hence the necessity for larger frames for enclosed motors.
Motors
seldom need to be fully enclosed unless they are to operate in very
dirty places, or in other special cases. A gauze enclosure such as that
indicated in Fig. 21 is satisfactory for most machinery applications.
A
IRON FOOT
LINE TERMINALS
CIRCUIT BREAKER
_-
NO-VOLTAGE
RELEASE COIL
MOTOR TERMINALS
Fig. 25.
Machinery, X.Y.
A
Circuit-breaker Starting Panel
Gauze or wire-netting enclosing covers reduce the rating
of a
motor
very little, if any. The use of such covers is advocated on motors for
nearly all machine drives.
The Code specifies that the frames of all motors operating at potentials in excess of 550 volts shall be either permanently grounded
or else insulated by wooden frames or otherwise. The use of a wooden
frame or any other insulating arrangement is not usually feasible, so
the almost universal practice is to bolt the motor frame into good
electrical contact with the frame of the machine.
It devolves upon
the purchaser of the machine to see that it is well grounded, either
through the conduit conveying the conductors to the machine (the
Code requires that the conduit of all conduit wiring systems be
grounded) or through a specially provided ground wire connected to
The Underwriters require that special permission be
obtained before motors with grounded frames are installed.
the machine.
THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW
AN INITIAL FINE OP
25
CENTS
WILL BE ASSESSED FOR FAILURE TO RETURN
THIS BOOK ON THE DATE DUE. THE PENALTY
WILL INCREASE TO SO CENTS ON THE FOURTH
DAY AND TO $1.OO ON THE SEVENTH DAY
OVERDUE.
JUN
NQV
i
LD
21-100m-7,'39(402s)
YC 53944
UNIVERSITY OF CALIFORNIA LIBRARY
MACHINERY'S DATA SHEET SERIES
MACHINERY'S Data Sheet Books include the well-known series of Data Sheets
originated by MACIUJNI v, and issued monthly as supplements to the publication;
of these Data Sheets over 500 have been published, and 6,000,000 copies sold. Revised and greatly amplified, they are now presented in book form, kindred subjects being
grouped together.
The
price of each book is 25 cents (one shilling)
delivered anywhere in tho world.
CONTENTS OF DATA SHEET
No. 1. Screw Threads. United States, Whitworth, Sharp V- and British Association Threads;
Briggs Pipe Thread; Oil W.-M Casing Gages;
Tin and Metric
Fire Hose Connections; AmuThreads; Machine, Wood, L;
ew, and Caretc.
Bolt
Threads,
riage
-1
No. 2. Screws, Bolt and !., ..
illister-head,
Headless, Collar-hear an<1 Hcxi, ^on-head Screws;
Standard and Sp-e':il Nuts; T-nuts, T-bolts and
Washers; Thumb Screws and Nuts; Machine Screw
Heads; Wood Screws; Tap Drills.
No. 3. Taps and Dies. Hand, Machine, Tapper
and Machine Screw Taps; Taper Die Taps; Sellers
Hobs; Screw Machine Taps; Straight and Taper
Boiler Taps; Stay-bolt, Washout, and Patch-bolt
Taps; Pipe Taps and Hobs; Threading Dies.
No. 4. Reamers, Sockets, Drills and Milling
Hand Reamers; Shell Reamers and ArCutters.
bors; Pipe Reamers; Taper Pins and Reamers;
Brown & Sharpe, Morse and Jarno Taper Sockets
and Reamers; Drills; Wire Gages; Milling Cutters;
Setting Angles for Milling Teeth in End Mills and
Angular Cutters, etc.
No. 5. Spur Gearing. Diametral and Circular
Pitch; Dimensions of Spur Gears; Tables of Pitch
Diameters; Odontograph Tables; Rolling Mill Gearing; Strength of Spur Gears: Horsepower Transmitted by Cast-iron and Rawhide Pinions; Design
of Spur Gears; Epicyclic Gearing.
No. 6. Bevel, Spiral and Worm Gearing. Rules
and Formulas for Bevel Gears; Strength of Bevel
Gears; Design of Bevel Gears: Rules and Formulas
for Spiral Gears; Diagram for Cutters for Spiral
Gears; Rules and Formulas fov Worm Gearing, etc.
No. 7. Shafting, Keys ana Keyways. Horsepower of Shafting; Strength of Shafting; Forcing,
Driving, Shrinking and Running Fits; Woodruff
Keys; Standard Keys; Gib Keys; Milling Keyways; Duplex Keys.
No. 8. Bearings, Couplings, Clutches, Crane
Chain and Hooks. Pillow Blocks; Babbitted Bearings; Ball and Roller Bearings; Clamp Couplings;
Flange Couplings; Tooth Clutches; Crab Couplings;
Cone Clutches; Universal Joints; Crane Chain;
Crane Hooks; Drum Scores.
No. 9. Springs, Slides and Machine Details.
Formulas and Tables for Spring Calculations; Machine Slides; Machine Handles and Levers; Collars;
Hand Wheels; Pins and Cotters; Turn-buckles.
No. 10. Motor Drive, Speeds and Feeds, Change
Power required for
Gearing, and Boring Bars.
Machine Tools; Cutting Speeds and Feeds for
Carbon and High-speed Steel; Screw Machine
Speeds and 1 ,-eds- Heat Treatment of High-speed
Steel Tools; 'i.-prTurning; Change Gearing for
Bars and Tools.
the Lathe; Bori
g.
'.OOFS
No.
11.
Milling Machine Indexinj
Clamping
Devices and Planer Jacks. Tables for vl tiling Machine Indexing; Change Gears for Milling Spirals;
Angles for sitting Indexing Head when Milling
Clutches; Jig Clamping Devices.
No. 12. Pipe and Pipe Fittings. Pipe Threads
Gages; Cast-iron Fittings; Bron/e F.'ttings;
Pipe Flanges; Pipe Bends; Pipe Clumps and
Hangers.
No. 13. Boilers and Chimneys. Fit;. Spacing
and Bracing for Boilers; Strength of BoiKT Joints;
Riveting; Boiler Setting; Chimneys.
No. 14. Locomotive and Railway Data. Locomotive Boilers; Bearing Pressures for Locomotive
Journals; Locomotive Classifications; R:iil Sections;
Frogs, Switches and Cross-overs; Tin-, Tractive
Force; Inertia of Trains; Brake Lever
and
No. 15. Steam and Gas Engines. -Saturated
Steam; Steam Pipe .Sizes; Steam Engine Design;
Volume of Cylinders; Stu'h'ng Boxes; Setting Corliss Engine 'Valve Gears; Condenser and Air Pump
Data: Horsepower of Gasoline Engines; Automobile Engine Crankshafts, etc.
16.
Mathematical Tables.
No.
Squares of
Mixed Numbers; Functions of Fractions; Circumference and Diameters of Circles; Tables for SpacFormulas
ing off Circles; Solution of Triangles'
for Solving Regular Polygons; Geometrical Pro:
gression,
Mechanics and Strength of Materials.
Centra ugal Force; Center of GravMotion; Friction; Pendulum; Falling Bodies;
No.
Work;
ity;
etc.
17.
En.-rjry;
Strength of Materials; Strength of Flat Plates;
Strength of Thick Cylinders, etc.
No. 18. Beam Formula and Structural Design.
Beam Formulas, Sectio ,al Moduli of Structural
Shapes; Beam Charts; Net Areas of Structural
Angles; Rivet Spacing; Splices for Channels and Ibeams; Stresses in Roof Trusses, etc.
No. 19. Belt, Rope and Chain Drives. Dimensions of Pulleys; Weights of Pulleys; Horsepower
of Belting; Belt Velocity; Angular Belt Drives;
Horsepower transmitted by Ropes; Sheaves for
Rope Drive; Bending Stresses in Wire Ropes;
Sprockets for Link Chains; Formulas and Tables
for Driving Chain.
No. 20. Wiring Diagrams, Heating and Ventilaand Miscellaneous Tables. Typical Motor
tion,
Wiring Diagrams; Resistance of Round Copper
Wire; Current Densities for Various Contacts and
Materials; Centrifugal Fan and Blower Capacities; Hot Water Main Capacities; Decimal EquivaMetric Conversion Tables. Weights and
lents,
Specific Gravity of Metals, Drafting-room Con.
ventions,
etc.
M
VCHINERY, the leading journal in the machine-building field, the originator of
Subscription, $2.00
the 25-cent Reference and Data Books. Published monthly.
yearly.
Foreign subscription,
$3.00.
The Industrial Press, Publishers of MACHINERY,
New York City, U.
140-144 Lafayette Street,
S.
A.
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