Smithy 1720 - Home-Machine

Smithy 1720 - Home-Machine
Smithy.
Operator’s Manual
MI-1720CNC
Lathe*MilleDrill
170 Aprill Drive « PO Box 1517
Ann Arbor, Michigan 48106-1517
lala ema rd. mdse Be ны
®Smithy. Midas 1720 Manual
Table of Contents
One: Introduction Page(s)
1.1 Customer information 7
1.2 Specifications 6
Two: Safety 8
Three: Caring for Your Machine 9
Four: Basic Parts 10-12
Five: Uncrating and Setting Up
5.1 Moving the machine 13
5.2 Uncrating and positioning the machine 14
5.3 Selecting a location 14
5.4 Cleaning and lubricating the machine 15-16
5.5 Setting lathe speeds 17
5.6 Setting mill speeds 17
5.7 Adjusting belt tension 18
5.8 Adjusting the gibs 18
5.9 Reducing backlash 19
5.10Running In 20
Six: Turning
6.1 Turning speeds 21-22
6.2 Gear ratios 22-23
Seven: Metalcutting Theory
7.1 Tool sharpness 24
7.2 Heat 24-25
Eight: Grinding Cutter Bits for Lathe Tools
8.1 High-speed-steel cutters 26-27
8.2 Materials other than steel 27
8.3 Bits for turning and machining brass 27
8.4 Special chip craters and chipbreakers 27
8.5 Using a center gauge to check V-thread forms 27
8.6 Acme or other special threads 28
8.7 Carbide-tipped cutters and cutter forms 29
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®Smithy. Midas 1720 Manual
Nine: Setting Up Lathe Tools
9.1 Cutting tool height
9.2 Turning tools
9.3 Threading tools
9.4 Cut-off, thread-cutting, and facing tools
9.5 Boring and inside threading tools
Ten: Setting Up with Centers, Collets, and Chucks
10.1 Centering
10.2 Mounting work between centers
10.3 Using a clamp dog
10.4 Using faceplates
10.5 Setting up work on a mandrel
10.6 Steady rests and follow rests
10.7 Setting up work in a chuck
10.8 Mounting work in a four-jaw independent lathe chuck
10.9 Mounting work in a three-jaw universal chuck
Eleven: Lathe Turning
11.1 Rough turning
11.2 Finish turning
11.3 Turning to shapes
11.4 Machining square corners
11.5 Finishing and polishing
11.6 Taper turning
11.7 Boring a tapered hole
Twelve: Lathe Facing and Knurling
12.1 Facing across the chuck
12.2 Knurling
Thirteen: Cutting off or parting with a lathe
Fourteen: Lathe Drilling Boring
14.1 Reaming
14.2 Boring
14.3 Cutting internal threads
14.4 Cutting special-form internal threads
Fifteen: Changing Gears
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32-33
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36
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@ Smithy. Midas 1720 Manual
Sixteen: Cutting Threads on the Midas 1720CNC Page(s)
16.1 Threading Terms 49-50
16.2 Cuttin right-hand threads 50
16.3 Using the treading dial 51
16.4 Cutting Multiple threads 52
16.5 What not to do when cutting threads 52
16.6 Finishing off a threaded end 53
16.7 Cutting threads on a taper 53
Seventeen: Milling
17.1 Holding Milling Cutters 55-56
17.2 Milling Cutters 57-59
17.3 Using Cutting fluid 60
17.4 Tool Gringing 60
17.5 Speeds and Feeds for Milling 61-63
17:6 Common Miling Operations 64
Eighteen: Workholding
18.1 Mounting to the table 65
18.2 Using a vise 65
18.3 Dividing heads 65
18.4 Rotary tables 66
Nineteen: Troubleshooting 67-71
Twenty: Parts Lists with Schematics 72-109
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DSmithy. Midas 1720 Manual
1.2 Specifications—Midas 1720 CNC
General dimensions: 42" long 22" wide 36" high
Crate size: 44" long 23" wide 38" high
Weight: shipping 600 1b, machine 500 Ib
Power: dual 3/4 hp, 110 V AC (0.55 Kw)
Mill/drillhead swivels
Calibrated dials
Leadscrew: 0.002"
Cross slide: 0.002"
Tailstock: 0.001"
Mill and drill: 0.040"
Lathe
Swing: over bed 17", over table 7"
Distance between centers: 20"
Spindle bore: 1.102"
Headstock taper: Morse taper #4
Tailstock taper: Morse taper #3
Speeds:Seven 160-1360 rpm
Thread pitches
Inch-thread: 40-120 tpi
Metric: 0.75 - 6 mm
Hardened, ground dovetail ways
Travel: cross slide 7.9 “, longitudinal 18.1”
5" three-jaw chuck with inside and outside jaws
Leadscrew Pitch: 6 tpi
Powerfeed rates .0002" - .014" rpm
Tailstock taper: Morse taper #3
Tailstock barrel travel 3.14"
Mill
Millhead taper: Morse taper #3
Spindle nose to table: 7.7" to 12.0"
Spindle to lathe faceplate: 11.2"
End Mills up to 1.1'
Face Mills up to 3"
Table: 6" wide 7-3/4" long
T-slot width: 7/16"
Quill diam: 3"
Quill travel:4.33"
Speeds: 16 (120 - 3000 rpm)
Working height: 6-1/4" min, 13" max
Drawbars
Standard: 3/8-16 tpi
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®Smithy. Midas 1720 Manual
SECTION ONE
INTRODUCTION
Congratulations on purchasing a Smithy lathe-mill-drill. We are pleased you chose Smithy to fulfill your
machining needs.
The purpose of this manual is to give the machinist, beginning or advanced, the information he needs to
operate the Smithy Midas 1720 CNC. It will teach you about the machine’s parts and how to care for them. In
fact, education is our primary goal. We'll explain how to grind cutters, set up lathe tools, hold workpieces, and
do all basic machining operations.
Please read this operator’s manual carefully. If you don’t understand how your machine works, you may
damage it, your project, or yourself. If you want to learn more about machining practices, Smithy offers books
that meet the needs of machinists at all levels of experience. We also suggest using your local library as a re-
source. Enrolling in a machining class will give you the best knowledge of machining.
If you have any questions not covered in this manual, please call Smithy. Our trained technicians will
help you with any machining problems you may have. Dial our toll-free number—1-800-476-4849—Monday
through Friday, 8:00 am to 5:00 pm Eastern Time. You can also find Smithy on the internet at www. smithy.com.
Check for service updates and service bulletins.
We are always interested in your suggestions to improve our products and services. Feel free to contact
as by phone or in writing. If you have comments about this operator’s manual, or if you have a project you’d
like to share with other Smithy owners, contact the Communications Director, Smithy Co., 170 Aprill Drive, PO
Box 1517, Ann Arbor, MI 48106-1517.
We look forward to a long working relationship with you. And thank you again for putting your trust in
Smithy.
1.1 Customer information
This manual should remain with your Smithy machine. If ownership changes, please include the owner’s
manual with the machine.
Model # + 7/ ДЕ 777
Serial #
(on the back of the lathe bed)
Purchase date гу an _ 7
| ño or ‚
Delivery date JS a J 7
sales technician и e e АО
Page7
®Smithy. Midas 1720 Manual
SECTION TWO
SAFETY
Your workshop is only as safe as you make it. Take responsibility for the safety of all who use or visit it. This
list of rules is by no means complete, and remember that common sense is a must.
* Know your machine. Read this manual thoroughly before attempting to operate your lathe-mill-drill.
Don’t try to do more than you or your machine can handle. Understand the hazards of operating a machine tool.
In particular, remember never to change speeds or setups until the machine is completely stopped, and never to
operate it without first rolling up your sleeves or tying them at your Wrists.
* Ground the machine. TheMidas 1720 CNC has three-conductor cords and three-prong grounding-type
receptacles. Never connect the power supply without properly grounding the machine.
* Remove all adjusting keys and wrenches from the machine before operating. A chuck key or misplaced
Allen wrench can be a safety hazard.
* Keep your work area clean and organized. Cluttered work areas and benches invite accidents. Have a
place for everything and put everything in its place.
* Keep children away from the machine while it is in use. Childproof your shop with padlocks, master
switches, and starter keys, or store the machine where children do not have access to it.
* Wear appropriate clothing. Avoid loose-fitting clothes, gloves, neckties, or jewelry that could get
caught in moving parts. If you have long hair, tie it up or otherwise keep it from getting into the machine.
* Use safety glasses, goggles, or a face shield at all times. Use glasses designed for machinery operation;
regular glasses will not do. Have extras for visitors. Know when to wear a face mask and earplugs, as well.
* Check for damaged parts. Make sure the machine will run properly before operating it.
* Disconnect the machine before servicing and when changing accessories. Shut power off before mak-
ing changes, removing debris, or measuring your work. Don’t reach over the machine when it’s operating. Keep
your hands out of the way.
* Avoid accidental starts. Turn the switch to Off before plugging in the machine.
* Secure your work. Flying metal is dangerous. Loose work can also bind tools.
* Use the recommended accessories. Understand how to use them before trying them out.
* Use the correct tool for the job. Don’t try to make a tool into something it isn’t.
* Keep your mind on your work. Pay attention to these simple rules and you will spend many safe,
enjoyable hours in your workshop.
Remember: your safety depends largely on your practices.
Page 8
BSmithy. Midas 1720 Manual
SECTION THREE
CARING FOR YOUR MACHINE
Your machine is a delicate, precision tool with hardened ways and hand-scraped bearing surfaces under the table
and carriage. Any rust spot or battering of the ways, any chips or grit between close-fitting parts, will affect the
accuracy of this fine tool. Follow these guidelines whenever you use your Smithy machine:
* When you finish working, wipe machined surfaces with a clean, oily rag. Never leave the machine
without this thin film of protective oil over all parts that might rust, especially ground finished parts.
* Never lay wrenches, cutting tools, files, or other tools across the ways of your lathe. The slightest dent
or burr will impair its accuracy.
* Before inserting collars, centers, adapters, or drawbar attachments in either the spindle or tailstock
spindle, wipe them with a clean, oily rag. Also, wipe all internal surfaces carefully with an oily rag on a ramrod.
Chips or dirt on the centers or in the spindle nose can scratch or mar surfaces and interfere with the assembled
part’s alignment.
* Lubricate the machine before each use (see Section 5.4).
* Use a good 10W 30 wieght non-detergent oil on your machine.
* Cover your machine to protect it from dust and moisture.
* An old machinist trick is to leave camphor in the toolbox and on the machine to prevent rust. Newer
compounds that also protect machines that will be unused for some time are BoeShield, developed by the
Boeing company und CRC lubricants. There are also speciality oils that may be purchased for your machine,
way oil for the ways and table of the machine and turbine fluid or 10 wt hydraulic oil for the headstock.
Page 9
BSmithy. Midas 1720 Manual
SECTION FOUR
BASIC PARTS OF THE Midas 1720 CNC
To leam the operations of your machine, you have to know the names and functions of its basic units.
* Bed. The bed is the machine’s foundation. It is heavy, strong, and built for absolute rigidity. The two
ways on the top are the tracks on which the carriage and tailstock travel. To maintain an exact relationship
between toolpoint and workpiece from one end of the machine to the other, the ways must be absolutely true
and accurately aligned to the line of centers and to one other.
* Carriage. The carriage consists of the saddle and apron. It moves by hand or power along the bed,
carrying the cross slide, compound rest, and toolpost. Its function is to support the cutting tool rigidly and move
it along the bed for different operations. It locks into place by tightening the carriage lock under the cross-slide
handwheel.
* Compound rest . Mounted on the cross slide, the compound rest swivels to any angle horizontal to the
lathe axis to produce bevels and tapers. Cutting tools fasten to a toolpost on the compound rest. The calibrations
on the front of the base are numbered in degrees from 60° right to 60° left.
* Cross slide. The T-slotted cross slide moves crosswise at 90° to the lathe axis by manual turning of the
cross-feed screw handwheel. It also serves as the milling table.
+ Drill press and fine-feed clutch. Pushing in the drill press clutch( engages the fine feed. To work the
clutch, release the spring tension by rotating the drill press handles clockwise. Pull the clutch out to use it as a
drill press or push it in to use the fine feed. Use the fine-feed handwheel to move the quill up and down.
* Forward/Off/Reverse switch. This is the main switch used to operate the lathe . It is simply a forward/
reverse switch for the motor. The motor turns counterclockwise for normal lathe operation and clockwise for
normal milling and drilling.
* Gearbox. The gearbox houses the belts that drive the spindle and change gears for the powerfeed.
Select the thread pitch (for threading) or the feed rate (for turning) by changing the four change gears on the
right side of the gearbox.
* Headstock. The headstock , which is secured to the bed, houses the gears that drive the powerfeed and
the taper bearings that secure the lathe spindle.
* Mill belt tensioner . To adjust the lathe belt tensioner, pull the handle forward to tighten the belt, back
to loosen it.
* Lathe spindle. The end of the lathe spindle facing the tailstock( is the spindle nose. The spindle nose,
which has an MT4 taper, rotates the workpiece and drives lathe chucks and other workholding devices. All
attachments (three-jaw chuck, four-jaw chuck, faceplate, etc.) bolt to the spindle flange either directly or via an
adapter plate.
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@Smithy. Midas 1720 Manual
* Leadscrew. The leadscrew which runs the length of the bed, moves the carriage for lathe turning or
thread cutting. It works both manually and under power. You can also use it manually with the mill.
* Locks. Locks on the cross slide, carriage, quill, and tailstock (two), keep them from moving. During
machining, lock all axes except the one you want to move.
* Micrometer control and calibration. Just inside the handles of the tailstock crossfeed, drill press,
compound feed, and leadscrew are collars calibrated in inches. The dial on the compound feed is also calibrated
in millimeters. The compound feed and crossfeed are calibrated in two thousandths, the tailstock in thousandths,
the leadscrew in two thousandths, and the drill press in forty thousandths.
These micrometer dial collars can move independently around the handle shafts. This independent
motion is called float. The Midas 1720 CNC has floating dials on the cross slide, tailstock, and leadscrew. They
let you zero the collars at any point and read the feed travel from that point on the dial for increased accuracy.
* Mill spindle. The mill spindle attaches to the quill, which moves in and out of the head. The quill lock
keeps the quill still when you install or remove tools from it and while milling horizontally. Usually, tools fit
into collets that attach through the spindle via drawbars.
* Half-nut lever. This lever transmits power to the leadscrew when rotated down.
* Power Cross-feed. Pull out on the knob to engage the cross-feed and push in to disengage.
* Powerfeed speed selector . The two-speed selector for powering the leadscrew is on the front of the
headstock. The leadscrew turns twice as fast in the II position as in the I position.
* Tailstock. The tailstock, which provides right-end support for the work, moves along the bed and can
stop at any point on it. It holds centers, drills, reamers, taps, and other tools. To move the tailstock spindle,
which has an MT3 taper, turn the tailstock handwheel. The scale of offset calibrations on the back of the
tailstock is in millimeters.
To offset the tailstock, loosen the four base-locking bolts. To offset to the left, loosen the left adjusting
bolt and tighten the right. To offset to the right, loosen the right adjusting bolt and tighten the left. (Figure 4:1).
4.1 To offset the tailstock loosen the four
bolts at the base of the tailstock.
Page 11
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Smithy. Midas 1720 Manual
SECTION FIVE
UNCRATING AND SETTING UP THE MI-1720CNC
Your machine is a delicate, precision tool with hardened ways and hand-scraped bearing surfaces under the table
and carriage. Any rust spot or battering of the ways, any chips or grit between close-fitting parts, will affect the
accuracy of this tool. Follow these guidelines whenever you use your Smithy machine:
* When you finish working, wipe machined surfaces with a clean, oily rag. Never leave the machine
without this thin film of protective oil over all parts that might rust, especially ground finished parts.
* Never lay wrenches, cutting tools, files, or other tools across the ways of your lathe. The slightest dent
or burr will impair its accuracy.
* Before inserting collars, centers, adapters, or drawbar attachments in either the spindle or tailstock
spindle, wipe them with a clean, oily rag. Also, wipe all internal surfaces carefully with an oily rag on a ramrod.
Chips or dirt on the centers or in the spindle nose can scratch or mar surfaces and interfere with the assembled
part's alignment.
* Lubricate the machine before each use (see Section 5.4).
* Use a good 10W 30 wieght non-detergent oil on your machine.
* Cover your machine to protect it from dust and moisture.
* An old machinist trick is to leave camphor in the toolbox and on the machine to prevent rust. Newer
compounds that also protect machines that will be unused for some time are BoeShield, developed by the
Boeing company and CRC lubricants. There are also speciality oils that may be purchased for your machine,
way oll for the ways and table of the machine with turbine fluid or 10 wt hydraulic oil for the headstock.
5.1 Moving the machine
Moving a machine tool can be dangerous. Improper techniques and methods may cause personal injury and/or
damage the machine. To find a professional to move and site your Smithy machine, look in your local Yellow
Pages under “Machine Tools, Moving and/or Rigging.” If there is no such listing or your community does not
have a rigging specialist, a local machine shop or machinist may be able to provide a referral.
When you pick up the machine at the shipping terminal, bring a crowbar, tin snips for cutting the metal
straps, and a hammer. If there is obvious shipping damage to the crate, you’ll be able to inspect the machine
before signing for it. Note any damage on the bill of lading (shipping document). Fill out the claims forms and
notify both Smithy Co. and the shipping terminal about the damage. Failure to notify both parties can compli-
‘ate and/or invalidate a claims process.
Trucking company terminals usually have forklifts to assist customers. Trucks without canopies and
large vans are the most convenient ways to transport the machines.
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BSmitiry. Mickas 1720 Manual
5.2 Uncreating and Setting Up Your Machine
The machine is assembled, inspected, and ready to goon its stand. It’s wrapped in a water and greaseproof
cover, strongly barced and crated. Your basic tool pack is included in your crate.
The metal bands that encricle the crate are under tension. Wearing eye protection and golves, cut the metal
bands with tin snips. Be careful-the cut edges are sharp. The bands secure the crate top to the base.
After removing the straps, you will need two people to remove the crate cover. With one person standing at
each end, grip the bottom of the crate lid. Lift straight up to remove the crate cover. Do not dispose of your
crate cover you may need it to transport your machine in the future.
Once the crate cover is removed, you will need to remove the machine from the skid and place it on a work
bench. There are four holes located in the bed of the Midas 1720CNC. Place a sturdy 3/4” pipe/rod through
these holes. It is best to use a engine hoist or some other lifting device with the aid of lifting straps/chain to
move your machine from the ground level to a work bench. Be sure to have have some friends or family mem-
bers with you to work as a spotter.
Once your machine is lifted onto a workstation, it is important that you secure it to your workstaion throu ght the
foot pads of your machine.
3.3 Selecting a location
There are several major considerations for selectiong a location for your Smihy.
Operation is from the apron side, so allow at leat 40-48” clearance in front of the machine.
The machine should be on a 20-amp circuit, positioned as close as possible to the power supply. Try not to use an
extension cord. If you must use one, check with an electrician about the proper size.
Provide ample working light over the operator’s shoulder.
Place the machine on a solid foundation-concreate, if possible. If you must put it on a wood floor, make sure it is
adequate. Brace it if necessary to prevent sagging or settling.
Make allowances at the back of the machine tool as well as at it s end and above it for later additions, attachments,
and or accessories. PRovide clearance on the left end for bar stock to be fend through the spindle. If you are
considering placing more than one machine in an area, allow endough floor space to feed long bar stock to ecah
machine.
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BOmitin. Mcas 1720Manual
5.4 Cleaning and lubricating the MI-1720CNC
Smithy machines are shipped with a protective grease coating called cosmoline. Use WD-40 or a noncorroseive
Kerosene to remove the cosmoline.
Once you have your Midas 1720CNC set up and postioned correctly, you ready for lubricating. You must do
this carefully and thoroughly before starting the machine. Use a pressure oil can and a supply of good-quality
SAE NO 10 weight oil..
Apply a ligtht layer of oil to the ways.
To be trorough and complete, follow this routine:
Oiling the Ways
Run the carraige as far to the left as pos-
sible. Put a few drps of oil on the ways.
Run the carriange to the extreme right and
repeat. You may want to use the waylube
an special oil formulated for the ways.
Oiling the Millhead Quill
Using your mill handles or your fine feed
crank lower the millhead down. Apply and
*hin layer of oil to the quill and work it up
and down a few times to spread the oil.
Place a few drops of oil here and use the drill
press handles to move the quill up and down to
work the oil.
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BSmithy. Midas 1720 Manual
Smithy machines are shipped with a protective grease coating. Use a non-corrosive kerosene to remove
the cosmolione.
Once you have the Midas-1720CNC set up and
postioned correctly, you are ready for lubricating. You
must do the caarefully and thoroughly before starting
the machine. ;USe a pressure oil can and a supply of
good-quality SAE 10 weight oil.
The be thorough and complete follow this routine.
Oiling the carriage
Lubricate the oil buttons in the cross-feed table.
There are two buttons on each side of the crossslide a
table (Figure 5:1). Using your oil can, oil each of these Figure 5:1
buttons.
Oil buttons on each side of the table
While oiling the buttons on your crosslide table, put a
few drops of oil on the compound and crosslides feed-
screws. Also the compound angle toolpost has two oil
buttons that should be oiled as well.
Oiling the Tailstock Oil buttons on tailstock
4
There are three oil buttons on top of the
tailstock that need to oiled. (Figure 5:2)
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@ Smithy. Midas 1720 Manual
5.5 Setting Lathe Speeds on the MI-1720CNC Figure 5:3
Setting Lathe RPM)
Changing belt positions on the MI-1720CNC changes A-F 160
speeds. Your machine comes with two v-belts, one long
one and one shorter belt. Use the longer belt between A-E 300
the lathe spindlepulley and the middle pulley. The
shorter belt is placed the motor pulley and the middle A-D 375
pulley. Use the the chart at the left to place your belts
and determine your lathe speeds. Remember, always B-F 470
make sure your motor is disengaged before changing
your belts. C-F 600
B-E 870
C-D 1360
5.6 Setting Mill Speeds on the MI-1720CNC
The mill changes speed in the same manner that the lathe does, by changing the belts. To set mill speeds, use
the two v-belts that come with your machine and use the chart below to determine the desired mill speeed.
Setting Mill/Dril Speeds (RPM)
| LL
B | ] E
| C 1] | | | G |
| D ] | H |
I |
Motor Middle Spindle
A-I B-1 A-H C-1 A-G D-I B-H A-F
120 200 310 350 400 450 530 600
B-G C-H B-E D-G C-F D-F C-E D-E
660 900 1380 1450 1670 2140 2350 3000
Figure 5:4
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®Smithy. Midas 1720 Manual
3.7 Adjusting belt tension on the MI-1720CNC
The MI-1720CNC has two belt tensioners installed by the factory, one for the millhead and one for the pulley
box. You will see a “L-shaped lever” positioned at the top of the millhead motor. To losen the tensiton, turn
the lever counter-clockwise.
On the back side of your machine there a handle directly above the lathe motor on the pulley box. Turn this
counter clockwise as far as it will go to losen the belts in the pulley box.
«Mill Belt Lathe Belt
. Tensioner
Figure 5:5 a Figure 5:6
5.8 Adjsuting the Gibs
The Midas has a tapered gib on the crossfeed and the straight gibs o n the carriage, the compound tool
post and the tailstock. Gib adjustment effects the tool rigidity and accuracy of the cuts.
As the gibs tighten, the effort it takes to move the controls increases. Adjsut the gibs according to the
Work you are doing and personal preference. Wha is importatnt is to adjust them evenly. The tigher the
gib, the more accurate it will be. Removing and polishing the gibs also improves the accuracy.
Crossfeed
The crossfeed gib is located under the crossfeed table and to the right. There is a screw at the rear of the
gib to lock it into place and a screw at the front of the gib to move it in and out (tighten or loosen).
Loosen the rear screw and then use the front screw to tighten or lossen the gib as desired. Check the
crossfeed for desired movement. Tighten the rear screw to lock the gib into position.
Carriage and Tailstock
The carriage and tailstock each have two gib adjustment points. Each point contains a locking set screw
and an adjusting set screw. Remove the locking set screw from each ajustment point. Tighten the
ajusting screws all the way, locking up any lateral movement. Then back the screws off 1/8” to /4” of a
turn and check the movement.
The effort to move the carriage or tailstock should be the same in both directions. If it is not, the gib is
not adjusted evenly. If there is more resistance felt moving to the right., the right gib is tighter than the
left and visa versa. As you work with the adjustments, you will feel the differerence even gib tensions
makes on the ease of movement.
When everything is set, reinstall the locking set screws to hold the ajustments in place.
Compound Tool Post
There are two gib adjustment screws on the tool post. They extend out the side of the tool post and are
locked inplace with a jam nut. Adjustment procedure is the same as the carriage and the tailstock.
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Smithy. Mas 1720Marua
5.9 Removing Backlash
Some backlash on the crossfeed and longfeed is normal, but to keep it to a minimum the thrust bearings on
each feed screw must be kept tight. The bearings are held in the proper position by two spanner nuts. The nuts
for the crossfeed are located on the front end of the screw under the crossfeed dail (M18717). The handle and
dial must be removed to asjust these nuts. The nuts for the longfeed are Icoated in the transmission box (part
NO. M10144) just below the powerfeed engagement lever. They may be accessed from under thetransmission
box.
Adjusting the spanner nuts to assure minimum backlash is the same for both screws. Using a pin punch,
loosen the outside locking nut and then the inside adjusting nut. Using the pin punch, slowly tighten the inner
adjusting nut until a light drag is felt on the screw when it is rotated. Tighten the outer locking nut with the
punch while frequently checking the ease of rotation of the screw. If the rotation of the screw becomes tight,
the adjusting nut has turned with locking screw. This can be corrected by loosening the adjustment nut slightly.
5.10 Running in the MI-1720CNC
Though all Smithy machines are run at the factory and again before shipping, it wise to put your machine
through a break-in run before puttin it to work. After oiling the machine, check the belts to make sure the
tensionis correct. Do not plug your machine in yet.
Follow these steps:
Make sure that the Forward/Off/Revesr switch for the lateh mtor and the mill motor are both in the off position.
If not already installed, screw the red stop button into the end of the stop switch. Pushing the red button in will
kill all power to the machine. The red button will stay in until it is reset. To reset the switch, turn the red
button clockwise until it pops out about 1/2 inch into the operation position.
Close the door on the end gearbox. The machine will not operate with the door open.
Plug the machine into a grounded 20-amp circuit.
Start the mill motor by placing the mill switch into “1” position. After a few minutes, switch the mill motor
“O” (Off) and allow the motor to stop. Repeat the procedure in the “2” position then turn the mill motor off.
Caution
This machine is equipped with power crossfeed and longitudinal feed.
Caution must be taken to not run the power feeds past their limits of travel. As part of normal operation
procedures, run each axis through the entire length of the proposed machining operation before engaging any of
the power feeds to assure there is sufficient travel to accomplish the desired task. Failure to do so could result
in running one of the power feeds to the end of its mechanical limits. This is what is know as a “CRASH”. A
crash can cause damage to the work piece and severe damage to the machine. Remember that becoming
familiar with your machine is the best safety insurance you can have.
Page 19
Smithy. Midas 1720 Manual
Place powerfeed selector in position III, the slowest speed.
Make sure all other powerfeed controls are in the disengaged position: Powerfeed engagment lever moved to
the right, half nut lever pushed down, and the crossfeed button pushed in.
Manually place the longfeed and the crossfeed in the center of their travel.
Start the lathe motor by placing the lathe switch into the “1” position.
Engage the powerfeed by moving the engagement lever to the left until the leadscrew starts to trun. Pull the half
nut handle up to the activate the longfeed, push it back down to disengage. Pull the crossfeeed button out to
activate the longfeed, push it back dwon to disengage. Pull the crossfeed button out to activate the crossfeed,
push it back down to disengage.
NOTE: If the crossfeed screw turns but there is no table movement, pull the table toward the operator
slightly while the power crossfeed is engaged. There is a void spot in the crossfeed thread to prevent the
table from being ran too far back (crashing the table). Some early machines did not have this safety
feature. Instructions are available through Smithy Company to modify the crossfeed screw on such
machines.
Turn the lateh switch to “O” and all wthe lathe to stop. Place the lathe switch to “2” amd repeat the powerfeed
run-in test.
During the run-in, try all the controls. Get a feel for your machine before starting to work.
Page 20
@ Smithy. Midas 1720 Manual
SECTION SIX
TURNING
The lathe rotates a workpiece against a cutting edge. With its versatility and numerous attachments, accessories,
and cutting tools, it can do almost any machining operation.
The modern lathe offers the following:
* The strength to cut hard, tough materials
* The means to hold the cutting point tight
* The means to regulate operating speed
* The means to feed the tool into or across, or into and across, the work, either manually or by engine
power, under precise control
* The means to maintain a predetermined ratio between the rates of rotating works and the travel of the
cutting point or points.
6.1 Turning speeds
When metal cuts metal at too high a speed, the too! burns up. You can machine soft metals like aluminum at fast
speeds without danger or trouble, but you must cut hard steels and other metals slowly.
You must also consider the diameter of the workpiece (Figure 6.1). A point on a 3"-diameter shaft will
pass the cutting tool three times as fast as a point on a 1"-diameter shaft rotating at the same speed. This is
because the point travels a tripled circumference. For work in any given material, the larger the diameter, the
slower the speed in spindle revolutions needed to get the desired feet-per-minute (fpm) cutting speed.
Lathes cut threads in various numbers per inch of material threaded, according to the operator's needs.
The Midas 1720 CNC cuts metric threads and inch threads standards.
In thread cutting, the carriage carries the thread-cutting tool and moves by rotating the leadscrew . The
basic principle is that the revolving leadscrew pulls the carriage in the desired direction at the desired speed. The
carriage transports the toolrest and the threading tool, which cuts the screw thread into the metal being ma-
chined.
The faster the leadscrew revolves in relation to the spindle, the coarser the thread. This is because the
threading tool moves farther across the revolving metal with each workpiece revolution.
The lathe spindle holding the workpiece revolves at a selected speed (revolutions per minute, or rpm)
according to the type and size of the workpiece. The leadscrew, which runs the length of the lathe bed, also
evolves at the desired rpm. There is a definite and changeable ratio between spindle and leadscrew speeds.
Figure 5.4 shows belt positions for various speeds.
Page 21
BSwithy. Midas 1720 Manual
6.1 Cutting Speeds for Various Diameters
FPM 50 | 60 | 70 | 80 | 90 | 100 | 110 | 120 | 130 | 140 | 150 | 200 | 300
DIAM RPM
1/16" | 3056 | 3667 | 4278 | 4889 | 5500 | 6111 | 6722 | 7334 | 7945 | 8556 | 9167 12229 | 18344
1/8" 1528 | 1833 | 2139 | 2445 | 2751 | 3056 | 3361 | 3667 | 3973 | 4278 | 4584 | 6115 | 9172
3/16" 1019 | 1222 | 1426 | 1630 | 1833 | 2037 | 2241 | 2445 | 2648 | 2852 | 3056 | 4076 6115
1/4" 764 | 917 | 1070 | 1222 | 1375 | 1538 | 1681 | 1833 | 1986 | 2139 | 2292 | 3057 4586
5/16" 611 733 | 856 | 978 | 1100 | 1222 | 1345 | 1467 | 1589 | 1711 | 1833 | 2446 | 3669
3/8" 509 | 611 713 | 815 | 917 | 1019 | 1120 | 1222 | 1324 | 1426 | 1528 | 2038 | 3057
7/16" 437 | 524 | 611 698 | 786 | 873 | 960 | 1048 | 1135 | 1222 | 1310 | 1747 | 2621
1/2" 382 | 458 535 | 611 688 764 | 840 | 917 | 993 | 1070 | 1146 | 1529 | 2293
5/8" 306 | 367 | 428 | 489 | 550 | 611 672 | 733 | 794 | 856 | 917 | 1223 | 1834
3/4" 255 | 306 | 357 | 407 | 458 | 509 | 560 | 611 | 662 | 713 | 764 | 1019 | 1529
7/8" 218 | 262 | 306 | 349 | 393 | 426 | 480 | 524 | 568 | 611 655 874 1310
1" 191 229 | 267 | 306 | 366 | 372 | 420 | 458 | 497 | 535 | 573 764 1146
1-1/8" 170 | 204 | 238 | 272 | 306 340 | 373 | 407 | 441 475 | 509 679 1019
1-1/4" 153 183 | 216 | 244 | 275 306 | 336 | 367 | 397 428 | 458 612 918
1-3/8" | 139 | 167 | 194 | 222 | 250 | 278 | 306 | 333 | 361 389 | 417 556 834
1-1/2" | 127 153 178 | 204 | 229 | 255 | 280 | 306 | 331 357 | 382 510 765
1-5/8" | 117 | 141 165 | 188 | 212 | 235 | 259 | 282 | 306 | 329 | 353 470 705
1-7/8" | 102 | 122 143 | 163 | 183 | 204 | 224 | 244 | 265 | 285 | 306 408 612
2" a5 115 134 153 172 191 210 | 229 | 248 267 | 287 382 573
2-1/4" 85 102 119 | 136 | 153 | 170 | 187 | 204 | 221 238 | 255 340 510
2-1/2" 76 91 107 122 137 153 168 | 183 | 199 214 | 229 306 459
2-3/4" 69 82 97 111 125 | 139 | 153 | 167 | 181 194 | 208 278 417
3" 64 76 89 102 115 127 140 | 153 | 166 178 191 254 371
Cutting Speeds
Figure 6.2 Al 24 | 30 | 36 | 42
Cutting Speeds for the Travel I 0.2 | 0.257 0.30 To35
MI-1720CNC A Do cl —
H | 0.1 | 0.12 | 0.15 [0.175
nm MM [II] 0.05 | 0.063 | 0.075 |0.088
Sor Travel |I {0.008 | 0.010|0.012 | 0.014
120T Per
| > Rev II [0.004 | 0.005 |0.006 | 0.007
INCH |IIl0.002 |0.0025/0.003 b.0035
Page 22
Table provides exact
speeds (rpm). It does
not take machine
speed limitations into
account. Determine
the desired rate of
speed and find the
closest speed
available on your
machine.
®Smithy. Midas 1720 Manual
* The means to hold the cutting point tight
* The means to regulate operating speed
* The means to feed the tool into or across, or into and across, the Work, either manually or by
engine power, under precise control
* The means to maintain a predetermined ratio between the rates of rotating works and the travel
of the cutting point or points.
6.2 Gear ratios
The lathe lets you use various indicated gear combinations to cut the desired number of threads per
inch (tpi), or the metric equivalent, or to advance the tool a specified amount each revolution (feed
rate expressed as inches per revolution [ipr]).
The MI-1720CNC has pick-gear gearboxes (Figure 14.1); gears are picked and placed to change the
gear ratios. The gearbox mechanism determines the leadscrew’s rotation rate in relation to the
spindle’s for threading, turning, and facing. To change the fee rate, replace the gears per Figure 6.2.
Page 23
@Smithy. Midas 1720 Manual
SECTION SEVEN
METAL CUTTING THEORY
7.1 Tool sharpness
Instead of being the all-important factor in determining tool performance, keenness of the cutting edge is
just one of many factors. On rough or heavy cuts, it is far less important than strength,
because a false cutting edge or crust usually builds up on the tool edge, and though the edge dulls, its angle
often increases the cutting tool's efficiency by increasing its wedging action. Cutter shape is usually more
important than edges, which generally are rough-ground and usually must be honed for fine finishing cuts
or work in soft, ductile materials like brass or aluminum.
Lack of clearance, which lets a tool drag on the work below the cutting edge, is a brake on the lathe,
greatly reducing pressure on the cutting point and interfering with tool performance more than edge dull-
ness. At the same time, excessive clearance weakens a tool because of insufficient support to the cutting
edge. Such an edge will break off if you use the tool on hard materials.
Clearance requirements change with almost every operation, but there are certain standards for all
aspects of the cutting tool. You must not only provide clearance from the cutting edge; there must also be
end and side clearance. To help the chip pass with minimum resistance across the top of the tool, it should
often have top rake as well. You determine the shapes and rakes to which you'll grind your tools by the
toolholder you use. The MI-1720CNC have a four-sided turret toolpost that accommodates four high-
speed-steel (HSS), carbide-tipped, or indexable carbide turning tools.
7.2 Heat
The energy expended at the lathe’s cutting point converts largely into heat, and because the energy ex-
pended is great, the heat is intense. Before today’s HSS, carbide, and ceramic tools, this heat created a
serious machining problem. Machining could be done only under a steady flow of coolant, which kept the
tool from heating to its annealing point, softening, and breaking down.
With HSS, vou can usually cut dry unless a small lathe is running at extremely high speeds on continu-
ous, heavy-duty production work. HSS tools are self-hardening even when red hot. They do not dissipate
the heat, however, or in any way prevent the workpiece from heating up. Because steel expands when
heated, it is a good idea, especially when working on long shafts, to check the tightness of the lathe centers
frequently and make sure workpiece expansion does not cause centers to bind.
Page 24
7.3 Cutting Speeds and Feeds for High-Speed-Steel Tools
Low-Carbon | High-Carbon | Alloy Steel Aluminum Cast Bronze
Steel Steel Annealed {| Normalized Alloys Iron
Speed (sfm)
Roughing 90 50 45 200 70 100
Finishing 120 65 60 300 80 130
Feed (ipr)
Roughing 0.010-0.202 | 0.101-0.020 | 0.010-0.020 | 0.015-0.030 | 0.010-0.020 | 0.010-0.020
Finishing 0.003-0.005 | 0.003-0.005 | 0.003-0.005 | 0.005-0.010 | 0.003-0.010 | 0.003-0.010
OSmitiy. Midas 1720 Manual
In everyday lathe operations like thread cutting and knurling, always usa a cutting oil or other
lubricant. On such work, especially if the cutis light and lathe speed low, dipping a brush in oil
occasionally and holding it against the workpiece will provide sufficient lubrication. For continuous,
high-speed, heavy-duty production work, however, especially on tough alloy steels, using a cutting
oil or coolant will increase cutting efficiency. It's essential if you're using a non-HSS cutting tool.
When you use coolant, direct it against the cutting point and cutter. Consider installing a coolant
system if you don't have one.
Figure 7.3 lists cutting speeds and feeds for HSS cutters so you can set up safe rpm rates. The
formula is as follows:
rpm = CS x 4 / D”
where CS = cutting speed in surface feet per minute (sfm) and D” = diameter of the workpiece in
inches.
To use this formula, find the cutting speed you need on the chart and plug that number into the
CS portion of the formula. After calculating the rpm, use the nearest or next-lower speed on the lathe
and set the speed.
If you were to make a finish cut on a piece of aluminum 1" in diameter, for example, you would
see the desired sfm per Figure 7.3 is 300. Then
rpm =300sfm x4 / 1
rpm = 1200 / 1
rpm = 1200 or next slower speed.
For high-carbon steel, also 1" in diameter,
rpm =50sfmx4/1
rpm = 200 / 1
rpm = 200 or next slower speed.
,_ The four-turret toolpost lets you mount up to four different tools at the same time. You can install
all standard-shaped turning and facing tools with 1" or smaller shanks. The centerline is approxi-
mately 5/8" above the bottom of the turret. Smithy also offers quick-change tool sets that greatly
speed up lathe operations. Contact a Smithy technician for details.
Page 25
®Smity Midas 1720 Manual
SECTION EIGHT
GRINDING CUTTER BITS FOR LATHE TOOLS
8.1 High-speed-steel cutters
The advantage of HSS cutter bits is you can shape them to exact specifi-
cations through grinding. This lets you grind a stock shape into any Г Pale
form. Stock shapes come in an assortment of types, including squares, —
flats, and bevels. Many shops buy their cutters as ready-ground or > 1 Angleof
ready-to-grind bits or blades. Side — Keenness
Clearance
3-10°
Ready-to-grind bits and blades are of specially selected HSS, cut to 8.1 Keenness angles vary from
length and properly heat-treated. They are fine tools in the rough and 60° to 90°.
generally superior to HSS shapes sold by the pound.
In grinding HSS cutter bits, you have five major goals:
* A strong, keen cutting edge or point
* The proper cutting form (the correct or most convenient shape
for a specific operation)
* Front clearance away from the toolpoint Front Clearance
3-15°
* Clearance away from the side of the tool (side rake) 8.2 The edge weakens if front
clearance is too great.
* Free chip movement over the tool and away from the cutting
edge.
Keenness angles can vary from 60° for mild softness to 90° for hard steels and castings (Figure 8.1).
Front clearance must always be sufficient to clear the work. If it is too great, however, the edge
weakens and breaks off (Figure 8.2). Side and back-rake requirements vary with the material used and
operation performed. Back rake is important to smooth chip flow, which is needed for a uniform chip
and good finish, especially in soft materials. Side rake directs the chip flow away from the point of
cut.
Grind cutters on a true-surfaced, good-quality, medium-grit grinding wheel (preferably an 8", 46—
60A-grit or 68A-grit Carborundum
wheel) at 6000 or 6500 rpm. When
starting with an unground cutter Cutter bit
bit, the procedure (Figure 8.3) is |
usually to (1) grind the left-side
clearance, (2) grind the right-side
clearance, (3) grind the end form or
radius, (4) grind the end clearance,
and (5) grind the top rake, touching
in a chipbreaker. If you are honin 1. Left-side 2. Right-side 3. End clearance 4 Radius 5. Top rake
the cu tting edge (for fine Finishing clearance clearance a op
or machining soft materials), draw
Grinding
wheel
8.3 Grinding sequence for an unground cutter bit.
Page 26
B8mithy. Midas 1720 Manual
the cutter away from the cutting edge across the oilstone
(Figure 8.4).
Oilstone
8.2 Materials other than steel
As pointed out earlier, when grinding HSS cutters, we
determine cutting angles primarily by strength require-
ments, not keenness requirements. Angles and rakes for
general industrial shop use are established. In machining
steel, the softer the steel, the keener the angle of the cutting
edge. For soft steels, angles as acute as 61° are possible 8.4 When honing, draw the cutter away from
(Figure 8.5). the cutting edge across the oilstone.
The same general rule applies to cast iron. Chilled or
very hard cast iron requires tools with cutting-edge angles
as great as 85°. For ordinary cast iron, you obtain greatest
efficiency with a more acute cutting edge—approximately
71° (Figure 8.6).
8.3 Bits for turning and machining brass
Brass tends to pull or drag when machined. It’s best to 8.5 With soft steels, 61° angles are possible.
machine it on dead center with the top rake in the hori-
zontal plane of the lathe centers. Softer than steel, brass needs less support for the cutting edge. Brass
cutters require an almost flat top angle and can gain greater angle keenness only in increased side and
end rakes. It is often advisable to hone the cutting edges of cutters used to machine brass.
Note: All roundnose cutters are ground with flat tops and equal side rakes because they are fed
across the work, to both right and left.
8.4 Special chip craters and chipbreakers
When grinding cut-off blades, and occasionally on other
cutter bits where the material's extreme hardness or
toughness makes it difficult to control the chip leaving the
work, it sometimes helps to grind a smooth, round crater 7
just behind the cutting edge. This serves as a chip guide
and starts the chip curling smoothly (Figure 8.7). 8.6 With cast iron, a 71° angle is most efficient.
8.5 Using a center gauge to check V-thread forms
It may be convenient to grind a standard cutter bit for thread cutting, especially for cutting standard
60° V-threads. When grinding an ordinary square cutter into a thread-cutting tool, take care to ensure
a true thread form. The easiest way is to use an ordinary center gauge for a standard V-thread tool or
a special thread gauge for special thread forms.
To grind a cutter for an ordinary V-thread, grind first the left side of the tool, then the right side, to
30°. Be careful to grind equally from both sides to center the toolpoint. Then test for true form by
inserting the newly ground point in the closest-sized V in a standard center gauge (Figure 8.8). Exam-
ine the gauge and cutter before a light. When the cutter is ground perfectly, no light streak shows
between tool and gauge. Use a grinding chart for other rakes.
Page 27
® Smithy. Midas 1720 Manual
8.6 Acme or other special threads
Thread gauges are available for all standard threads. Before grinding
such cutters, ascertain the correct pitch angle of the particular thread
profile. For example, the pitch of an acme thread is 29” to a side, and
the toolpoint is ground back square to an exact thread profile that
requires a different end width for each thread size.
Thread forms must be accurate if threads are to fit snugly and
smoothly. Every resharpening of this type of cutter requires
regrinding the entire form. Itis far better, when doing any amount of
threading, to use a threading tool with a special form cutter. Sharpen-
ing such cutters requires only flat, top grinding, which does not alter
8.7 A crater starts the chip curling
the cutting profile.
smoothly.
8.7 Carbide-tipped cutters and cutter forms
Carbide is a compound of carbon and a metal. In cutting п
tools, it is usually carbon and tungsten. The hardness of я
carbide cutting materials approaches that of diamond.
While carbides permit easy machining of chilled cast
iron, hard and tough steels, hard rubber, Bakelite, glass,
and other difficult or “unmachinable” materials, its
primary use in industry is for long production runs on
ordinary steels. On such work, carbide-tipped tools що
permit higher ing speeds and much longer runs 8.8 Insert the point into the nearest-sized V in the
center gauge.
between resharpenings. The cutting gag
edge of carbide tools stands up 10
to 200 times as long as the edge of : ati
; 8.9 Carbide Types and Cutting Tool Applications
HSS tools (Figure 8.9). JP 9 PP
Application Use Grade
The advantage of carbide is that | |
it tolerates much higher heat than Cast irons Roughing cuts Ci
HSS or other alloys so you can run Nonferrous, nonmetallic, General purpose C-2*
at higher speeds. The disadvantage high-temperature alloys
is that it is more brittle than HSS 200 and 300-series Light finishing C-3
and must have adequate support in stainless steels Precision boring C-4
the toolpost to prevent vibration Roughing cuts C-5
and breakage. General purpose С-6*
Alloy steels Finishing cuts C-7
400-series stainless, Precision boring C-8
high-velocity
*C-2 and C-6 are the most commonly used carbides.
Page 28
Smithy. Midas 1720 Manual
SECTION NINE
SETTING UP LATHE TOOLS
After selecting a cutter, insert it in the toolholder. Allow the cutter bit to project just enough to provide the neces-
sary clearance for the cutting point. The closer the cutter is to the toolpost, the more rigid the cutting edge. Allen-
head capscrews hold the tool in the toolpost. To assure maximum
rigidity, don’t let the tool extend too far beyond the end of the toolpost
turret.
9.1 Cutting-tool height
After inserting the cutting tool into the toolpost, adjust the height of
the cutting edge in relation to the lathe center. Insert a center in the
tailstock. Then run the tool and center together. The cutting edge on
the tool should meet the point on the center. It may be necessary to use
shims, which can be of various thicknesses and materials (Figure 9.1).
Many seasoned machinists use
pieces of old hacksaw blades
as shims. If the toolbit is too
Figure 9.1 Placing shims under the high, shim the back of the
tool can correct tool height. toolbit. If it’s too low, shim the
entire tool.
9.2 Turning tools
For general turning operations, set the point of the cutter bit slightly above
the centerline of the work. In steel, the harder the material, the less above
center (Figure 9.2, top). Exceptions are soft brass, aluminum, and materi-
als that tend to pull or tear. When machining these materials, set the cutter
on dead center (Figure 9.2, bottom.)
When cutting toward the headstock on most turning and threading opera-
tions, swing the compound rest to hold the shank of the toolholder at an
angle. The angle should be approximately 29-1/2° left of perpendicular to Figure 9.2 The harder the steel
the line of centers, except for extremely heavy, rough-forcing cuts close to (top) the less above center you
the limits. For such work, use a straight-shanked
tool held perpendicular to the line of lathe centers in
the right side of the toolpost. The tool will tend to
swing out of the cut rather than hog into the work if
you reach a stalling point (Figure 9.3)
9.3 Threading tools
Threading tools should always engage the work on
dead center. Any deviation above or below will
affect the thread profile (Figure 9.4).
Figure 9.3 The tool will swing out of the cut (left)
rather than hog into the work (right) if you reach a
stalling point. Note the tool is in the right-hand side.
Page 29
®8mithy. Midas 1720 Manual
Page 30
9.4 Cut-off, thread-cutting, and facing tools
For cutoff, thread cutting, and facing, feed the cutter to the
work on dead center (Figure 9.5). For the beginner, the average
feed should not exceed 0.002 inches per revolution (ipr).
9.5 Boring and inside threading tools
For boring and inside threading, the cutter point engages the
work on dead center (Figure 9.6). For greater cutting efficiency,
9.4 Threading tools engage the workon position the bar while parallel to the line of lathe centers suffi-
dead center. ciently below center to give the cutter a 14-1/2° approach
angle. For internal threading, grind the top face of the cutter to
compensate for this angle, giving a flat, true-form top face.
Some machinists prefer to position the tool slightly above center when boring. With the bit above
center, if a tool chatters it deflects down into empty space instead of into the workpiece.
Chip Curve
un
O
9.5 Feed the cutter on dead center for
cutoff, thread cutting, and facing.
9.6 For boring and inside threading, the cutter pointis at
dead center.
SSmithy. Midas 1720 Manual
SECTION TEN
SETTING UP WITH CENTERS, COLLETS, AND CHUCKS
Before setting work up on centers, make sure the
spindle and tailstock centers align accurately. Do this by
inserting a cen-ter into the nose spindle and inserting the
tailstock center into the tailstock ram. Then move the
tailstock toward the headstock until the centers touch (Figure
10.1). You can cor-rect any lateral alignment error by adjust-
ing the tailstock set-over screws (Figure 4.8).
10.1 When aliani indle and tailstock For most turning operations, work is held in the lathe
centers moy a Listo ck on the between the lathe centers by means of holes drilled in the
headstock until the centers touch. ends of the stock to be machined. Your machining accuracy
depends primarily on how precisely you locate these holes at
the center of the bar or block. Locating these holes is called centering.
10.1 Centering
You can improve centering greatly by first squaring or facing the ends of the workpiece (Section
12.1). This gives you a true cross section in which to locate the centering holes. First, chuck the stock
in the appropriate chuck. Let the stock protrude about an inch. Place a right-hand side tool (or a
straight turning tool with a facing cutter) in the toolpost. Carefully adjust the cutting edge so it is
exactly on center, then tighten it into the toolpost. If you don’t do this, a small tit or projection will
remain in the center of the stock and perhaps cause the center drill to run off center.
Start your lathe on the slowest speed. Bring the tool into the cutting position against the center of
the workpiece. Feed the tool from the center of the stock outward, toward yourself, using the hand
crossfeed. One or two light cuts is usually enough to true up an end roughened by the hacksaw. After
facing one end, reverse the work and face the opposite end.
You can center on round stock (Figure 10.2) with calipers, dividers, or special centering instru-
ments (Figure 10.3). Centering square or rectangular stock is done by scribing lines from opposite
corners. The intersection of these lines is the center (Figure 10.4).
After locating the center of each end, drive a starting depression for the drill into the stock with a
center punch. Check centering accuracy by placing the workpiece between the spindle and tailstock
centers. Revolve the headstock slowly against the tip of a tool or a piece of rigidly held chalk. The
chalk should touch just the high spots (Figure 10.5). If the center is off 0.002" or
more, correct the
position of the
center by
repunching at an
angle.
Next, drill and
countersink the
centers to conform
10.2 Centeri 10.3 Use centering instruments 10.4 C to the profile of the
‚се Lentering on 10. \ trur .4 Centering on square This i
round stock. include calipers and dividiers. or rectangular stock. lathe centers. This is
Page 31
Smithy. Midas 1720 Manual
77
LP." пе
0 Too shallow >
Chalk
Compound
> |
Correct depth 1
4
10.5 When you revolve the headstock against a piece of chalk, the
chalk should just touch the high spots.
Too deep Г
best done with a combination center drill / countersink held in the |
tailstock arbor chuck. The centers now will take the lathe centers
without play or chatter. 10.6 The correct depth of center
is illustrated above. If it's too
If a combination drill is not available, you can drill centers with a deep (bottom), only sharp outer
ии \ edges will contact the center,
small drill and countersink them with a drill of sufficient diameter
ground to a 60° point. A 60° taper is standard for lathe center points.
Correct center depth is given in Figure 10.6. Take care to get an accurate 60° countersink in the center
(Figure 10.7).
10.2 Mounting work between
centers
Remove the chuck from the lathe, bolt
the faceplate to the spindle flange
(Figure 10.8), and put in both head-
stock and tailstock centers. Fasten a Lathe
lathe dog (Figure 10.9) to one end of A pon B C
the work. For ease of operation, use a
live or rotating center in the tailstock 10.7 Counterbore centers with a drill to a 60° point so they fit the lathe
end so you won't need lubrication. centers (A). Too obtuse (B) or too acute (C) a counterbore will give
Before starting the lathe, make sure the insufficient bearing, prevent accuracy, and destroy the lathe centers.
centers don’t hold the workpiece too
tightly. Heat may cause the workpiece to expand, so watch for binding. Adjust the tailstock center so
the work turns freely but without end play.
If, after partially machining the workpiece, you find you must
machine the stock under the lathe dog, remove the workpiece from
the lathe and place the lathe dog on the machined end. Then turn
this new tailstock center end of the shaft down to the desired
diameter or form.
10.3 Using a clamp dog
Standard lathe dogs drive round, or near-round, shapes. Rectangu-
lar or near-rectangular stock requires clamp dogs. In a properly
made clamp dog, the underface of the heads of tightening screws
are convex and fit into concave seats, while the holes in the upper E. | u
bar are elongated. This design allows a firm grip of off-square 10.8 Bolt the faceplate to the spindle
shapes without bending the screws. Top and bottom bars should flange.
Page 32
BSmithy. Midas 1720 Manual
Faceplate also have V-notches to give a firm grip on triangular or other
: odd-shaped stock. You can use clamp dogs or special V-jaw
dogs also to hold highly polished round bars.
10.4 Using faceplates
For work setup, faceplates serve two purposes. First, they
drive workpieces held between centers. Second, they hold
workpieces shaped so you can’t chuck them or mount them on
centers.
N НЕ
saab TN Faceplates for driving workpieces on centers are generally
10.9 Fasten a [athe dog to one end small. They're notched and slotted to receive the tail of the
of the workpiece. lathe or clamp dog, bolt drive, or other driving tool (Figure
10.9). Faceplates for holding workpieces (irregularly shaped
casting, machine, or die parts, for example) are usually larger and of varied design. They may be
T-slotted, drilled all over, or slotted and drilled. Workpieces mount on such faceplates with T-slot or
standard bolts, strap clamps, angle plates, or other standard setup tools.
Note: Before starting to machine work set up on centers,
check to see the lathe dog tail is free in the faceplate slot so it a
won't lift stock off its true line of centers, as in Figure
10.10. Also, be sure lathe centers fit closely into the center
holes to eliminate side play but not so tightly they bind. If
you're working on a long workpiece, check it frequently to
be sure the center does not bind. Also, balance unbalanced
setups with counterweights to overcome any “throw” as the
work revolves (Figure 10.11).
Jai of lathe dog
10.5 Setting up work on a mandrel 10.10 Make sure the lathe dog tail is free in the face-
plate slot so it won't lift off the true line of centers.
You can machine cylindrical or bored pipe work or
cored castings too long to fit in a chuck by mounting them first
on a mandrel (Figure 10.12). Then mount them between centers. 4
The solid mandrels, which are driven into the hole of the work-
piece, must be tight enough to turn the workpiece against the tool | Ш
without slippage. Oil them lightly before driving them into the TT
workpiece. Otherwise, the workpiece may freeze to the mandrel,
making it impossible to remove the mandrel without damaging
both workpiece and mandrel. When removing a mandrel, drive it U?
back out of, instead of through, the hole.
10.11 Counterweights can help with
You can purchase hardened steel mandrels, which have a unbalanced setups.
slight (0.003") ground taper and an expanding collar, to facilitate
mounting and demounting (Figure 10.13). Mandrels with compressible ends for holding single or
ganged pieces are also available. When a workpiece is mounted on a mandrel, machine it as you
would a solid shaft. You can drill eccentric centers in mandrel ends to permit eccentric turning.
10.6 Steady rests and follow rests
Rests are for setting up (1) work that is relatively long in proportion to its diameter or (2) work whose
dead end must be left free for boring or other operations. You can also use rests to machine slender
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@Smithy. Midas 1720 Manual
Page 34
shafts that are apt to spring out of alignment from the thrust of
Workpiece the tool. The purpose of a rest is to support the workpiece and
( maintain it in accurate alignment for machining. Rests are
classed as steady rests or follow rests.
Steady rests. Steady rests mount on the lathe bed (Figure
10.14). Clamped over the ways, they provide three bearing
Mandrel surfaces. These surfaces bear down lightly but rigidly against
the surface of the shaft and keep it from moving out of the line
10.12 Mount workpieces too long for of the lathe centers. You can place a steady rest anywhere along
a chuck on a mandrel. the bed where it will best support and steady the workpiece
without interfering with the operation.
To set up a steady rest, first center the work in the chuck and true it
up. Then slip the steady rest into position and tighten it to the bed. With
the bearing jaws clearing the work, close the top of the rest and tighten
the locking screw. Now, with the lathe running, adjust the three bearing
jaws to touch, but not push, the workpiece. Finally, test again for align-
ment, making sure the axis of the workpiece coincides with the axis of
the lathe. Otherwise, the end will not be square and the surfaces and
boring will be untrue. The tips of the jaws are bronze and require lubri-
cation.
10.13 Hardened steel mandrels
Follow rests. Long or slender shafts that are apt to spring out of have a slight ground taper and
alignment by the thrust of the cutting tool often require a follow rest expanding coltar.
(Figure 10.15). Follow rests mount on the carriage of the lathe and move with the tool, backing up the
workpiece opposite the point of the tool thrust. They have two adjustable supporting jaws, one hold-
ing the work to keep it from climbing up on the tool and the other behind the work to counter the
thrust of the tool.
Note: Take great care in adjusting the jaws of rests, as they must form a true axial bearing for the work and
let it turn freely but without play.
10.7 Setting up work in a chuck
Chucks usually hold work that is too short to hold conveniently between centers or work requiring
machining at, into (boring or inside threading), or across its end.
While it is possible to set up such work on a faceplate, the conve-
nience of chucks has made them part of every complete lathe. Lathe
chucks come in many types and sizes and hold workpieces of
diameters approaching the swing of the lathe.
For ordinary use, there are two standard types of headstock
chucks. The four-jaw independent lathe chuck has four holding jaws
that can operate independently and adjust to hold round, square,
eccentric, or odd-shaped work (Figure 10.16). The three-jaw univer-
sal geared scroll chuck holds only round or near-round work with
three, six, nine, 12, or other multiple-numbered sides. It always
holds work concentrically. The three-jaw chuck has the advantage of
being self-centering—all jaws move in or out together (Figure 10.17).
10.14 Steady rests mount on the
lathe bed and provide three bearing
surfaces.
10.8 Mounting work in a four-jaw independent lathe
chuck
For small-diameter, short work, insert jaws in the chuck with high
ends to the center. This gives the maximum gripping and tool
clearance (Figure 10.18). For large-diameter work, insert the jaws
in the chuck slots with the high steps of the jaws to the outside of
the chuck (Figure 10.19).
To place work in a chuck, follow these steps:
* Adjust the chuck jaws to the approximate opening to receive
the work. Roughly center them by matching the nearest concen-
tric ring on the chuck face with the corresponding mark on the
jaws.
* Place the work in the chuck and grip it. Turn up the opposing jaws
a uniform number of turns with the key provided. This will hold the
Work in position. Then bring in the other pair of opposing jaws the same
Way.
* Revolve the spindle slowly with your left hand while holding a
piece of chalk until the chalk touches the high point (the nearest surface)
of the work (Figure 10.6).
MSmithy. Midas 1720 Manual
10.15 Follow rests mount on the lathe
carriage and move with the tool.
10.16 Four-jaw independent
* Guided by the chalk marks, readjust the jaws until a chalk line will 'athe chucks hold round,
carry completely around the work. Then tighten all the jaws securely. Square, eccentric, or odd-
shaped workpieces.
For greater accuracy, after roughly centering the stock using chalk, set
a dial indicator at the back of, and square to, the stock. Make sure you can see it clearly. Rotate the
chuck by hand. Looking at two opposing jaws, determine which side is higher Align the higher side
with the dial indicator, loosen the opposite jaw, and tighten the higher jaw. Do the same with the
other two jaws. Repeat the process until you have located the stock within necessary tolerances.
When making several identical pieces, after completing each workpiece release only two adjoin-
ing jaws, leaving the others to hold the center. The jaws of the four-jaw independent chuck are revers-
ible. You can insert them with high steps to the inside or outside.
O
<>
O
10.17 Three-jaw universal 10.18 For short, small-diameter
geared scroll chucks hold round workpieces, insert the jaws with high
or near-round work. ends to the center.
1
|
mu
10.19 For large-diameter workpieces,
insert the jaws with the high steps of
the jaws to the outside.
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®Smithy. Midas 1720 Manual
Page 36
Never leave the chuck key (wrench) in the chuck while the chuck is on
the spindle. Any movement of the spindle can crash the key into the
ways, seriously damaging the ways, spindle, and chuck. Turning
on the lathe with the key in the chuck can seriously damage your
lathe. The key can also be thrown when the lathe starts, causing
damage and/or injury. Never let your hand leave the chuck key
unless you are picking it up or storing it.
Never remove a chuck or heavy faceplate without first laying a
board across the ways to protect them in case the chuck falls when
it comes off the spindle nose. Or use a chuck cradle to ease chuck
removal and installation. 10.20 A serial number is stamped in
the #1 slot of the three-jaw chuck.
10.9 Mounting work in a three-jaw universal chuck
Slot #1 Slot #3
Work is set up in a three-jaw universal chuck as in a four-
jaw independent chuck, with these exceptions:
* On three-jaw chucks, the key moves all the jaws at
once.
* You need not center or check for concentricity
because these chucks center automatically.
* Jaws are not reversible. Each chuck comes with two
sets of jaws. One is for setups with high steps toward the
inside (inside jaws), the other for mounting in the chuck
with high steps to the outside (outside jaws).
. . . , 10.21 With the slot for the #1 jaw in
* When installing the chuck jaws on a three-jaw chuck, the 12:00 position, the slot for the #2
install them in numerical order and counterclockwise jaw is at 8:00 and the slot for the #3
rotation. jaw is at 4:00.
Each jaw is stamped with a serial number and jaw number (#1, #2, or #3). The slots in the chuck
are not numbered, but there is a serial number stamped at the #1 slot (F igure 10.20). With the #1 slot in
the 12:00 position, the #2 slot is at 8:00 and the #3 slot at 4:00 (Figure 10.21).
To install the jaws, first insert the #1 jaw into the #1 slot and turn the key until it engages. Then
put in the #2 jaw and engage it, then the #3 jaw.
10.10 Collets and collet attachments
To hold small-diameter work, whether bar stock fed through the hole
in the spindle or small pieces of semifinished parts, collet attachments
are preferable to standard chucks (Figure 10.22) for several reasons:
* They have much faster release and grip actions.
* They center the work automatically and accurately.
i
{
|
X
—_
10.22 Collet attachments are best
for small-diameter work.
* They grip even small pieces and pieces with a short hold firmly.
BSmithy. Midas 1720 Manual
* They are housed within the spindle nose for maximum tool clearance, making it possible to
machine, thread, or cut off close to the spindle.
While chucks are universal tools that hold a range of stock sizes and shapes, collets are special
tools. There is a collet for every size and shape of workpiece.
Made with extreme accuracy, hardened, and ground, standard split collets are slotted so their jaw
ends compress inwardly to grip the workpiece. This is done by pulling the collet jaw's externally
tapered shoulder into a matching taper-bored adapter sleeve. The adapter sleeve connects the lathe
spindle's MT5 taper to the collet's MT3 taper. A drawbar holds the collet in place.
10.11 Toolpost grinders
A fully equipped lathe has a toolpost grinder, a small, independently operated grinding head with an
integral electric motor that mounts as a unit in the toolpost T-slot of the compound rest. (For lighter
work, some are held in the toolpost.) You can maneuver it as you would any other cutting tool.
Toolpost grinders come with wheels of different shapes, sizes, and grits for grinding different
materials and surfaces. They also come with arbors and mounted wheels for grinding internal sur-
faces. You can use them to grind or polish surfaces; to grind lathe centers, arbors, taper sockets, leader
pins, gauges, valve seats, and other close-fitting parts; and to sharpen tools.
Page 37
Smithy. Midas 1720 Manual
SECTION ELEVEN
LATHE TURNING
11.1 Rough turning
In turning a shaft to size and shape where you have to cut away a lot of stock, take heavy, rough cuts to get
the work done in the least time. With the MI-1720cnc use a transverse powerfeed for heavy cuts—from right
to left toward the headstock so the thrust is against the head-stock or the chuck. Use a right-hand turning or
roundnose cutter.
Remember caution must be taken to not run the powerfeed past their limits of travel.
As part ofthe notrmal operation, procedures, run each axis through the entire length
of the proposed machining operation before engaging the powerfeed to assure there
is suficient travel to accomplish for the desired task. Failure to so so could result in
running the power feed to the end of its mechnical limit. This is what is known as
a “CRASH”. A crash can cause damage to the work piece and severe damage to the
machine.
After selecting a cutter, place it into the left side of the turret . The cutter’s point should be just above or on
the line of the centers. The greater the diameter of the work, the higher the cutter can be. Adjust the height by
placing shims under the cutter and raising or lowering it (Figure 9.1).
With the tool properly positioned, tighten the Allen capscrews. Next, run the carriage to the right end of
the workpiece with the hand crank. Make sure the lathe is set to feed toward the headstock. Now determine the
depth of the cut. Move the tool to the desired depth till it just touches the stock and zero the cross-feed dial.
Start the lathe. Run the crossfeed in by hand to take as heavy a cut as is consistent with the power of the
drive or the amount of metal to remove.
Say, for example, you need to reduce a diameter by a known number of thousandths of an inch. If you zero
the collar and watch the movement of the dial, you’ll know the depth of the feed from the zeroing point. Note:
The dial gives a good approximation, but for exact measurements, use a measuring instrument.
To reduce the diameter, advance the tool only half as many thousandths on the dial. This is because the
tool takes off an equal amount from both sides as it cuts a continuous strip around the work. For example, to
reduce the diameter of a shaft 0.005", you advance the tool only 0.0025", or
1-1/4 calibrations.
Engage the tool before setting the floating dial. The tool must be moving in the direction you want to go
before you set the dial to zero to compensate for the backlash.
For a screw to move, there must be some play in the thread. When backing the cutting tool away from the
cut, move the feedscrew enough to take up the backlash before setting the collar or when drawing the tool
from the cut.
Engage the longitudinal feed by moving the powerfeed engagement lever left and then pulling the half nut
lever up. Always cut deeply enough to reach below the scale on oxidized bars or iron castings. Hard, oxidized
surfaces dull tools rapidly.
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BSmithy. Midas 1720 Manual
11.2 Finish turning
After you've rough-turned the workpiece to approximate finished size (within 1/32"), replace your
cutter bit with a freshly ground, keen-edged cutter. Make one or
more light finishing cuts across the machined machined surface.
Check the diameters carefully with a caliper or micrometer to
be sure you are working to proper dimensions. Remember: the
diameter will reduce twice the thickness of the cut.
For rough turning, most machinists prefer a deep cut and a
comparatively fine feed, but the reverse is true for finishing cuts.
They usually use a very light crossfeed and a coarse transverse
feed with a cutting edge wider than the feed per revolution. In TE
Figure 11.2, the left-hand tool illustrates the first roughing cut and ne Roughing (left) and finishing (right)
the right-hand tool shows the following finishing cut.
Cutting too!
11.3 Turning to shapes
Other turning cuts, machining shapes, corners, fillets, etc., are done the same way. The main difference
1s in selecting cutter bits and maneuvering the cutting point by means of various cutting tools.
Left-hand Right-hand
turning turning
Turning with a roundnose cutter
>
Left-hand y ,
facing ) ан: Right-hand *
Finishing cut facing
Left-hand Y Parting or | 4
corner cutting off Î 1 Right-hand
a corner
Special-form cutter
11.3 You can do other turning cuts with different cutter bits and cutting tools.
11.4 Maching Square Cornors
To machine an accurate cornor, follow these steps:
Page 39
B8mithy. Midas 1720 Manual
Page 40
* Set the compound rest perpendicular to the line of the centers
and insert a right or left-hand corner tool.
* Using the longitudinal feed, turn a small diameter to finish up to
the shoulder.
* With the compound rest, feed the tool the amount needed to
finish the work to the length, taking the last facing cut across the
shoulder away from the center.
11.5 Finishing and polishing
After machining, you'll want a smooth, polished surface free of
machine marks. You'll obtain the best results with a toolpost grinder.
If you don't have one, use a file.
With a file, take full, biting strokes across the revolving workpiece
at a slightly oblique angle. Do not drag the file back across the work-
piece; instead, lift it clear for each return stroke. Use a clean, dry file
and keep the workpiece clean, as well. Wipe the workpiece dry and
clean if you've used coolant or cutting oil. Never hold the file station-
ary while the workpiece is revolving (Figure 11.4).
For an even finer file finish, rub railroad chalk into its teeth. This
provides additional lubrication and absorbs filings. Do not use black-
board chalk.
11.4 With a file, take full strokes at
an oblique angle; never hoid the
file still.
N
11.5 You can polish a workpiece
with an abrasive cloth and oil.
After filing off the machining marks, polish the workpiece with emery or other abrasive cloth.
Keep the lathe turning at high speed and spread a few drops of oil on the workpiece. Don't stop
moving the cloth (Figure 11.5).
11.6 Taper turning
There are two ways to turn a taper: with the compound rest and by setting over the tailstock. In both
methods, the cutter must engage the work on dead center if the taper is to be accurate.
Compound rest. Tapers cut with the compound rest are usually
short, abrupt angles, such as centers, bevel gear blanks, and die parts
(Figure 11.6). In general, these are not considered taper turning,
which applies to machining longer, more gradual tapers.
Setting over the tailstock. Cutting tapers by setting over the lathe
tailstock involves misaligning the lathe centers. The lathe centers
move from their position parallel to the tool's transverse travel,
giving the desired degree of taper (Figure 11.7). The tailstock has a
set-over scale calibrated both forward and backward from the
straight turning or zeroing point for measuring set-over distances.
To offset the tailstock, loosen the two base-locking bolts (Figure
4.8). To offset to the right, loosen the right adjusting bolt and tighten
the left. To offset to the left, loosen the left adjusting bolt and tighten
the right.
Figure 11.2 Tapers cut with the
compound rest are usually short,
abrupt angles.
You can turn long, gradual tapers
by setting over the tailstock, but take
care. Your computations must be nearly un
perfect, because an error will spoil your J
work.
The distance of tailstock setover
needed to machine any given taper
depends on three factors:
B8mithy. Midas 1720 Manual
* The differential between the 11.7 In setting over the tailstock, the lathe centers move from their
finished diameters of the extreme ends Parallel position with the tool’s transverse travel.
of the taper
The length of the taper in relation to its extreme diameters, if the entire shaft is to be tapered
The ratio between the length of the tapered portion to the entire length of the shaft (or work
between centers when you're tapering only part of the shaft.
When the taper extends
the entire length of the
workpiece, tailstock setover
should equal half the dif-
ference between the fin-
ished diameters of the ends
(Figure 11.8). When a taper
extends only part of the
length of the shaft, divide
the total shaft length by the
length of the portion to be
tapered. Then multiply the
resulting quotient by half
the difference between the
extreme diameters of the
finished taper.
Notes: (A) Because most
11.8 Tailstock setover should be half the difference between the finished diameters
of the ends, or O=T" x L"/2, where T= taper per inch and L=length of work in
inches.
drawings give the taper in inches per foot of length, it may be easier to convert all dimensions to inches. (B) Be
sure to zero the tailstock before resuming straight turning.
11.7 Boring a tapered hole
Boring a tapered hole involves setting the compound at the desired degree of taper and feeding the
tool with the compound rest. Make sure the compound rest is set at half the degrees of the angle of
the completed taper hole. You can also use a taper attachment to bore a tapered hole.
Page 41
B8mithy. Midas 1720 Manual
SECTION TWELVE
LATHE FACING AND KNURLING
Before removing your work from the centers, face or square up the ends. On accurate work, especially where
shoulders, bevels, and the like must be an accurate distance from the ends, do the facing before turning the
shank. This also cleans the ends and machines the workpiece to accurate length.
When diameters are large, it’s best to face with a special side tool that has a long, thin blade with a wide
cutting edge. If you don’t have one, use a right or left-hand facing cutter. Feed the tool from the center outward
to avoid marring the lathe center (Figure 12.1).
12.1 Facing across the chuck
When facing a stub-end workpiece held in the headstock —
chuck, the same rules apply. Chuck the stock, letting it pro-
trude about an inch. Place a right-hand side tool (or a straight
turning tool with a facing cutter) in the toolpost. Carefully
adjust the cutting edge so it is exactly on center, then tighten it
into the toolpost. If you don’t do this, a small tit or projection
will remain in the center of the stock and perhaps cause the
center drili to run off center.
— —
Start your lathe on the slowest speed. Bring the tool into
cutting position against the . Do not start with a heavy feed 121 With a facing cutter, feed the tool from the center
because the sfm increases rapidly as the cutter moves through |
increasing peripheries. One or two light cuts is usually enough
to true up an end roughened by the hacksaw. After facing one end, reverse the workpiece and face the opposite
end.
If you must finish the ends of the shaft, use a half-center (Figure 12.2). This lets you extend the tool across
the entire face of the work.
To use the powerfeed for facing, place the powerfeed selector into position III before the lathe is turned on.
Once teh cutter has been positioned as per the above paragraph, move the leadscrew lever to the left and pull
the crossfeed. Push the button in at the endo of the cut to stop the cutter travel.
12.2 Knurling
Strictly speaking, knurling is not a machining operation because
no metal is cut. It is a forming operation in which patterned
knurls are pressed into the work, depressing and raising the
surface of the metal into a pattern. As with all other forming i |
operations, your work can be no better than the pattern, your — 3
knurling no better than the knurls. Be sure the knurls are sharp, |
clean-cut (preferably hob-cut), and properly hardened.
To make a true, uniform knurl, maintain uniform pressure on
both knurls. Select a self-centering knurling tool that equalizes
pressure on the knurls automatically and is strong enough to
withstand end and side thrusts. Operate the lathe at the slowest
speed (160 rpm).
Page 42
12.2 With a half-center you can extend the tool
across the entire face of the work.
BSmithy. Midas 1720 Manual
Knurling exerts extreme thrust against centers and bearings. You can
lessen this thrust materially by feeding the knurling tool at a slight angle
off from perpendicular to the line of the workpiece. This engages the
right side of the knurl first (Figure 12.3).
Place a few drops of oil on the workpiece and knurling tool. Start the
rolls of the knurling tool from the right-hand scribe line and feed them
in until the knurl reaches a depth of 1/64". Then stop the lathe and
inspect the work. If the knurl is not clear-cut, adjust the tool in or out as
needed.
Use plenty of oil, lubricating both knurl and workpiece. Then start
the lathe and engage the automatic feed, moving the knurls across the
portion to be knurled. When you reach the left scribe line, force the tool
into the work another 1/64", reverse the lathe without removing the
tool, and feed it back to the starting point. Feed both ways using the
automatic longitudinal feed. Once across, each way, usually makes a angle of g the a Da Sight
line of the workpiece.
Page 43
B8mithy. Midas 1720 Manual
Page 44
SECTION THIRTEEN
CUTTING OFF OR PARTING WITH A LATHE
You can cut off in a lathe only when holding one end of the work rigidly, as in a chuck. It is not
practical for long workpieces held between centers because the workpiece is not supported closely
with a rest and the free section is long enough to sag and pinch the blade. Cutting off requires a tight
lathe without excess play in the spindle, compound, carriage, or toolpost. Looseness will almost
certainly cause chatter. Cutting off also requires a narrow cutting edge with ample (5-10°) side clear-
ance, which should feed into the work slowly to prevent hogging in. Once considered a difficult,
costly operation, cutting off became much simpler with development of narrow tools with special cut-
off blades (Figure 13.1).
The toolpost should hold the cut-off tool as close to the
workpiece as possible, with the top of the blade on dead
center and exactly perpendicular to the line of centers.
Extend the blade only far enough to pass through the work-
piece, just beyond its center. The tool should feed to the
workpiece on exact center, slowly and evenly with the cross-
feed. If the tool hogs in and the spindle stops rotating, turn
off the motor and reverse the spindle by hand before backing
the tool out with the crossfeed. 13.1 Specially designed tools like this one
make cutting off easier.
Always set up the workpiece to cut off as close as pos-
sible to the headstock. If you must make a parting cut on a long shaft or on work between centers,
don’t complete the cut in the lathe. Finish the parting with a hacksaw and return it to the lathe for
facing. Slow the spindle speed until you have a good feel for cutting off. Although lubricants and
coolants are not essential on small-diameter workpieces, use them amply on deep cut-off work.
®Smithy. Midas 1720 Manual
SECTION FOURTEEN
LATHE DRILLING AND BORING
You can lathe drill on the MI-1720CNC in two ways, holding the drill stationary and revolving the
workpiece, or holding the workpiece stationary and 7
revolving the drill. Holding the drill sta-tionary in a
tailstock chuck gives a straighter hole (Figure 14.1).
Without changing setup and recentering, the work is ready
for any succeeding operations, such as boring and internal
threading.
„ан
In all lathe drilling operations, keep the drill sharp and sm
properly ground. This is essential for obtaining a straight, 14.1 Holding the drill stationary in the tailstoc
accurate hole. chuck gives a straighter hole.
With HSS drills, operating speeds are not as critical as with carbon-steel drills. High speeds can
quickly “burn” a carbon-steel drill. The number-of-feet-per-minute rule applies to drills even more than
to other cutting edges because there is practically no air cooling of the point after it enters the hole.
The larger the drill, the greater the number of peripheral feet cut per revolution. That is why you
should use a slower drilling speed. If no drilling speed data are available, it’s generally safe to run
drills under 1/4" diameter at up to 750 rpm and drills up to 1/2"
diameter at 500 rpm, with larger drills at proportionately slower
speeds.
With the workpiece in the headstock and the drill in the
tailstock chuck, feed the drill into the workpiece by advancing |
the tailstock ram. Do this by turning the tailstock handwheel. 14.2 A tool with a smooth-ended bar won't
Make a locating center for the drill point, or even a countersunk mar the workpiece.
center for large diameters, to keep the drill from creeping.
14.1 Reaming
When a hole must be accurate to 0.002" or less, drill it slightly undersized (0.010" to 1/64" on small
diameters and 1/64" to 1/32" on holes 1" to 2" in diameter).
Then ream it either by hand or in the lathe.
Lathe reaming is usually done with solid reamers held in
a tailstock chuck or with a taper shank that fits the tailstock
ram in place of the tailstock center. Use slow speeds and
feed the reamer slowly and evenly into the workpiece. Be
sure the reamer teeth are free of burrs and chips.
14.2 Boring
Boring is internal turning, or turning from within. The
diameter of the opening to be bored is often much smaller 14.3 Chamfer a starting cut in the opening of
than its depth. Boring tools must therefore have relatively the hole.
small diameters and still support a cutting edge projected at considerable distance from the toolpost or Pages
compound rest.
BSmithy. Midas 1720 Manual
Page 46
Boring tools consist of an extremely stiff, strong bar
with a formed cutting end or a way to hold an HSS cutter
or carbide insert. There are many sizes and types of
boring bars. Choose the one that will give the stiffest
possible bar at every depth and diameter and the greatest
choice of cutters and cutter angles (ask a Smithy techni-
cian about the Smithy boring head combo package, #K99-
125).
It is also wise to select tools with smooth-ended bars
without a projecting nut or hardened edge that might mar
the work (Figure 14.2). Most boring tools have only one
cutting edge. There are double-end cutters, however, and
they offer advantages in special instances. In grinding 14.4 The cutting edge engages the workpiece
cutters, allow sufficient end rake to provide clearance along a line in the mounted plane of the lathe
from the internal diameter. centers.
Except with cored castings, pipes, or tubing, begin by
drilling a hole large enough to admit the end of the boring bar.
Because the holes in cored castings often deflect boring bars
from their true axis, you may want to chamfer or turn out a
starting cut in the opening of the hole to be bored with a turn-
ing tool (Figure 14.3) before introducing the boring tool.
With the boring toolholder set up (in the toolpost or toolpost
T-slot, depending on the type), select the largest-diameter
boring bar whose cutter the bore will accept. Extend the bar
from the holder just enough to reach the full depth to be
machined and still allow tool clearance. Except when using the
adjustable boring tool (usually for very-large-diameter work),
feed the bar into the hole, parallel to the hole's axis. The cutting
edge engages the work along a line in the mounted plane of the
lathe centers with the bar positioned to give the cutter a top
rake of approximately 14° from the radius at the cutting point
(Figure 14.4). This takes into consideration the ground angle (top
rake) of the cutter itself.
For straight longitudinal cuts, you can hold the cutter close
up, therefore more rigidly, if it's at a 90° angle to the bar. For
machining ends of a bar, however, you need a boring bar that
holds the cutter at an angle or angles so the cutter extends
beyond the end of the bar (Figure 14.5). For maximum visibility,
position the cutting edge at the near side, parallel to the
centerline.
The rules that apply to external turning apply to boring as
well, except—as noted earlier—where the rake angles differ.
The rake angles are governed by cutter type and bore diameter.
Feeds must be lighter to keep the tool from springing. This is
especially true when enlarging out-of-round holes, when you
take several small cuts rather than one heavy cut.
14.5 To machine ends of a bar, use a
boring bar that angles the cutter so it
extends beyond the bar.
à Center
gauge
- - CHEF LE
to correct cutter alignment error
when squaring the cutter with the
workpiece.
After the last finish cut, it is common to reverse the feed
and take one last, fine cut with the tool coming out of the
work. This last cut, taken without movement of the cross-
feed, avoids a slightly undersized hole because you compen-
sate for any spring in the bar.
14.3 Cutting internal threads
Internal thread cutting is like external thread cutting, except
you have the clearance restrictions and tool problems of
boring. You use the same toolholders, but the cutters have
thread forms and are fed at thread-cutting ratios of feed to
spindle revolutions.
Another difference between boring and inside
threading is the cutting angle at which the cutter
approaches the workpiece. As with external thread
cutting, the internal threading tool must engage the
work on dead center and be held so the cutter
coincides with the workpiece’s center radius.
In squaring the cutter with the work, use a
center gauge (Figure 14.6) or thread gauge. Internal
cutters require greater end and side clearance, and
cutter length is also restricted because internal
thread cutters must have enough end clearance that
the cutter lifts clear of the thread for removal (Figure
@Smithy. Midas 1720 Manual
14.7 There must be enough end clearance
for the cutter to lift clear of the thread.
14.8 Use different clearances between nut and screw
for different thread types.
14.7). Before cutting an internal thread, bore the workpiece to the exact inside diameter.
Because the feed of successive cuts is toward, not away from, the operator, the thread-cutting set
is reversed. Also, you must take lighter cuts because of the cutter’s extension from the toolpost. Take
an extra finishing cut without changing the setting of the compound rest.
14.4 Cutting special-form internal threads
You can cut internal forms in all the thread forms used for external threads. There is only one factor
that calls for special attention in cutting special-shaped internal threads: the difference of clearances
between the nut and screw recommended for different thread types (Figure 14.8). If you don’t have
recommended clearances, it is safe to cut a nut thread (internal thread) 0.005" to 0.010" per inch larger
in the screw’s outside diameter.
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@ümithy. Midas 1720 Manual
SECTION FIFTEEN
CHANGING GEARS
To change geras on the MI-1720CNC, follow these steps. You will need a 17 mm wrench
and a5mm allen wrench.
Remove the nuts from A and D gear shafts, loosen the B/C gearshaft by turning it counter
closckwise with the allen wrench. This lets the shaft slide freely along the bracked for easy
gear removal.
Adjusting Bolt
Figure15.1 SlideB/C gearshaft until theC gear meshes
with the D gear
Slide the B/C gearsahft until the C gear meeshes proberly with the D gear and tighten in with the
allen wrench. (Figure 15:1).
Place the selected A gear on tha gearshaft and replace the nut and washer.
Swing the bracket assembly untl the A and B gears mesh. Hold the bracke assembly in place and
tighten the bolt. Make sure the gears turn smoothy before engaging the powerfeed. You may need to make
some adjustments.
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Smithy. Midas 1720 Manual
SECTION SIXTEEN
CUTTING THREADS ON
THE MIDAS 1720CNC
16.1 Threading terms
Before beginning to cut threads, it’s useful to learn the major terms used in thread cutting:
* Pitch. Metric pitch is the distance from the center of a thread to the center of the next thread. To
measure pitch in inches, measure an inch on a bolt and count the threads.
* Pitch diameter. This is the diameter of an imaginary cylinder superimposed on a straight screw
thread, the surface of which would make an equal width of the thread and the spaces cut by the cylin-
der.
* Lead. The lead is the distance a screw thread advances axially
(as through a nut) with one complete revolution. The lead and pitch
of a single thread are identical, but they differ on multiple threads
(the lead of a double thread is twice its pitch; of a triple thread,
three times its pitch).
Because screw-thread cutting is so generally a part of machine
work, anyone interested in building things of metal should master it.
Threading requires patience and skill. Before attempting to cut a
thread on a workpiece, cut a few practice threads on odd bits of
steel, iron, and aluminum. 16.1 Check dead center with a credit
card.
Built for thread cutting, the MI-1720CNC cuts stan-
dard internal and external threads, as well as special
threads. You may cut coarse or fine threads in a great
range of threads per inch, in V or square shapes, in estab-
lished profiles like Unified National, acme, and metric.
You can cut single threads or multiple threads that run
concurrently along the shaft. You determine the type of
thread by how you'll use the screw. Each thread form
requires a different-shaped tool to cut or chase it.
For most work, beginners use the Unified National
Standard, which is a V-form thread slightly flat on top and a
at the root. Screw threads are usually referred to by pitch igure 16.2 \ e compound perpendiculat
numbers, such as 18 or 24, meaning 18 or 24 threads per to the line of centers, rotate it 29.5 degres to
inch (tpi). The MI-1720CNC cuts standard threads in the right.
pitches from 4 to 120 tpi and metric threads from 0.75 to
6 mm. (See Figure 16:9)
Because the lathe spindle, which carries the work, connects by gearing to the leadscrew, which
moves the cutting tool along the lathe bed, a ratio exists between spindle speed in revolutions per
minute and cutting tool movement in inches. When you change the gearing, you change this ratio. For
this reason you can cut screw threads of various pitches by changing both the pick-off gears at the head
of the lathe and the speed selection lever.
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®Bmithy. Midas 1720 Manual
Thread charts on the front of your machine show both inch and metric measurements. The inch chart
shows the tpi from 4 to 120. The metric shows the distance from thread crest to crest from 0.075 to 6 mm.
For right-hand threads, start the threading or chasing tool at the right end of the workpiece and feed it toward the (
headstock. For left-hand threads, reverse the leadscrew’s rotation direction and feed the threading tool from left to
right.
With practice, you can grind cutters to almost any profile.
It 1s difficult, however, to sharpen such cutters without alter-
ing the cutting form, and almost every resharpening requires a
complete regrinding of profile and clearance angles.
y
After turning the work to be threaded to the outside Workpiece |
diameter of the thread and setting the gears for the desired
thread, put a threading tool in the toolpost. Set it exactly on
the dead center of the workpiece you'll be threading.
To make sure your cutter is on dead center, place a credit
card or shim between the cutter point and workpiece (Figure
16.1). When the tool is on dead center, the credit card or shim
will remain vertical. With a credit card, there is no possibility 16.3 Using a center gauge, set the threading tool perpen-
of chipping the cutter as the workpiece and cutter come dicular to the work piece.
together.
Set the compound perpendicular to the line of centers and rotate it 29-1/2° to the right (Figure 16.2). Place the |
thread gauge on the point of the threading tool and feed the tool toward the work-piece (Figure 16.3). Adjust the
tool so the edge of the gauge is exactly parallel to the workpiece. A slip of white paper held below the gauge will
help check the paralle] of the gauge to the shaft and the fit of the toolpoint in the V of the gauge. Placing the
threading tool perpendicular to the surface of the workpiece assures a true-form thread.
16.2 Cutting right-hand threads
Now you are ready to cut right-hand threads. First, advance
the tool so it just touches the workpiece and turn the com-
pound calibration back to zero. Then, using the compound
feed, feed in the too! 0.002". Next, turn on the lathe and
engage the powerfeed lever by carefully turning it one-quarter
turn to the left. Do not force it, and do not disengage it until
you are completely done.
It is best to take a light, scratch cut first without using
cutting fluid. After the tool runs the desired length, turn off the
lathe and back the tool out of the work. Then reverse the
motor to return the tool to the starting position. Using a screw-
pitch gauge, check the thread pitch. The benefit of taking the
light cut is that you can correct any mistakes you might have
made.
16.4 Chamfer the end of the thread to protect it from
damage.
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@Smithy. Midas 1720 Manual
16.3 Using the Threading Dial
The threading dail performs the
function of idicating the proper time to
engage the half-nuts so that the cutting
tool will enter the same groove of the
thread of each successive cutting pass.
This allows the half-nut to be disengaged
resulting in an easier method of
threading. Atthe end fo each consecutive
pass the half-nut can be disengaged and
the carriage can be moved back to the
start of the thread without stopping the
spindle or reversing the motor.
Disengage the half-nut, back the cutter
away from the workpiece and move the
cutter back to the beginning of the thread
with the hand wheel. Turn the cutter the
desired amount and you are ready fo the
next threading pass. The threading dial
is marked with lines numbered 1,2,3,4,5 and 6 and a single reference line on the houseing of the dial (Figure 16.5).
The indicator table (Figure 16.6) on the front of the trheading dial show the selection for the different thread
pitches. Find the desired thread pitch under the “TPI” column and engage the half-nut at the proper numbeers
shown on the “SCALE” column of the table. “1-6” means the half-nut can be engaged on any of the numbered
lines 1 through 6. “1,4” means that the half nut can be engage on 1 or 4 only. For any thread pitch not listed on the
chart, cut a test thread and engage the half nut on 1 or 4 only. If the test cut in not successful, the thread dial can not
abe used and the instructions from the previous section should be followed. Cutting of metric threads cannot be
done with the trhead dial.
Figure 16:5 Note numbers on top of
the threading dail when cutting threads.
INDICATOR SCALE
TPI| SCALE |TPI | SCALH TPI | SCALE |TPI BCALE
8 | 14 12 | 1-6 |20 | 1,4 32 11,4
9 | 1-6 14 | 1,4 |22 | 1,4 40 |1,4
10 | 1,4 16 | 1,4 | 24 | 1-6
11 | 14 18] 1-6 |28 |1,4
Fiqure 16.6 Threading Dial Indicator Scale
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B8mithy. Midas 1720 Manual
Page 52
It's time to take the real cut now, so apply the
appropriate cutting fluid to the work. Feed the À
compound feed in 0.005—0.020" for the first run, il
depending on the pitch of the thread you have to | | |
cut. If you are cutting a coarse thread, start by \
taking a few heavy cuts. Reduce the cut depth for | |
each run until it is about 0.002" at the final run. = —
Zero the cross-feed calibration, then make the Single Thread Double Thread Triple Thread
second cut. 16.7 When cutting multiple threads, increase the lead to make
room for succeeding threads.
Continue this process until the tool is within
0.010" of the finished depth. Brush the threads regularly to remove chips. After the second cut, check the thread
fit using a ring gauge, a standard nut or mating part, or a screw thread micrometer It is best to leave the piece in
the chuck and not remove it for testing.
After returning the workpiece to the setup, continue taking 0.001-0.002" cuts. Then check the fit between
each cut. When you thread the nut, it should go on easily but without end play. When you have the desired fit,
chamfer the end of the thread to protect it from damage. To chamfer is to take a 45° cut off the end of the bolt
(Figure 16.4).
16.4 Cutting multiple threads
Cut multiple threads (Figure 16:7) one at a time exactly as you cut single threads, except increase the lead to
make room for succeeding threads (a double lead for a double thread, a triple lead for a triple thread, etc.). After
completing the first thread, remove the work from the centers without loosening the lathe dog. Then put it back
in the lathe with the tail of the lathe dog in the correct slot to index the work for the next thread. This work
requires a faceplate with accurately positioned slots, uniformly spaced and equal in number to the number of
threads to be cut.
16.5 What not to do when cutting threads
Do not disengage the powerfeed engagement lever. Do not shift the
powerfeed speed lever. If you are cutting between centers, don’t
remove the lathe dog until the thread is finished and tested, and
don’t disturb the spindle while the work is off the centers.
When you think the thread is finished and ready for testing, and
only if absolutely necessary, remove the
16.8 When cutting a thread on a taper, set
the threading tool at 90° to the axis of the
taper.
BSmkthy. Midas 1720 Manual
workpiece from the center, leaving the lathe dog attached. Then test the thread. If it does not fit |
properly and you have to remove another chip or two, place the workpiece back in the centers exactly
as it had been. Then remove the chips and test again. Repeat until you are finished. |
16.6 Finishing off a threaded end
After cutting a thread and before removing the threading tool, chamfer the end. This improvesits
appearance and removes sharp corners and burrs. It also aids the screw as it engages a nut or
threaded hole.
16.7 Cutting threads on a taper
Cut threads on a taper the same as on a straight shaft, except in the setup of the tool. Set the threading
tool at 90° to the axis of the taper, rather than at 90° to its surface (Figure 14.8).
Figure 16:9 Threading Charts
Sl =n —
A— a MIDAS 1720 CNC
УМУ ` THREAD CHART FOR
INCH THREADS
127 To
— [AT] 24 [27 ]30 [33 ] 36 Tas Taz Tas Too
11 4145 [3 6 165177 370
10 N 72 || sio | 10 | 1 | 12 | 13 | 14 Г 16120
Inch m| 16 | 18 | 20 | 22 | 24 | 26 | 28 | 321 40
_ I 18 24 30
D — 24 [Tr 27 | 30 | 33 ae HS 60
I 54 | 60 | 66 72 | 78 84 | 96 120
mm
A mm 7 MIDAS 1720 CNC
VA THREAD CHART FOR
METRIC THREADS
1277 ——
A 36 42 48 60 72
120T — N I 0.75 1 1.25 1.5
nn ch II 15 1.75 2 2.5 3
24T—| | TI 3 3.5 4 5 6
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DSmithy. Midas 1720 Manual
Page 54
SECTION SEVENTEEN
MILLING
In milling, one or more rotating cutters shape a workpiece held by a vise or other fixture. The cutters mount on
arbors or at the end of the spindle on collets or adapters.
Machinists use mills to machine flat surfaces, both horizontal and vertical, and to make shoulders, grooves,
fillets, keyways, T-slots, and dovetails. They can also make curved and irregular surfaces and machine accurate
holes. Its variety of machining operations and high metal-removal rates rank the mill in importance with the
lathe.
The millhead rotates 180 degrees. A quill that moves in and out of the head carries the spindle.
You can move the table horizontally in two directions by turning the cross-slide and long-feed handwheels
The cross-slide handwheel turns the table longitudinally (at right angles to the spindle axis); the long-feed hand
crank moves it transversely (parallel to the spindle axis).
To rotate millhead, loosen dual locks located on front of machine and push in the desired direction.
Remmeber you millhead swivels 180 degrees, do not force it past its mechanicals stops. (Figure 17:1).
Figure 17:1 Millhead Rotated 90 Degrees
BSmilley. Midas 1720 Manual
Drawbar
(
17:1 Holding Milling Cutters
There are several ways to hold milling cutters:
in arbors, with collets and special holders, and
in adapters. Arbor
Arbors
Arbors come in different sizes and lengths, with
one end tapered to fit the bore in the end of the
machine spindle. The arbor of the MI-1720CNC, which has an MT3 taper, is driven by the friction
between the arbor and spindle. The arbor stays in place by means of a drawbar
screwed into the end of the arbor from the top of the spindle (Figure 17. 1).
17:2 The arbor stays in place via a drawbar.
Take good care of your arbors. Store them in a rack or bin. If you won’t be
using them for several days or longer, oil them to prevent rusting, especially in
damp weather.
Collets and holders
Straight-shank end mills fit into spring collets (Figure 17.2) or end mill holders _ |
(Figure 17.3). Their precision-ground shanks go into the mill spindle. When you Into the mile fit \
tighten a spring collet, its hole reduces in size and the collet grips the end mill straight-shanked end mills.
shank evenly. Tighten the end mill securely with the setscrew against the flat
surface of the end mill, or it may slip out and damage the workpiece, the cutter, or you.
Adapters
Adapters mount various types and sizes of cutters on the spindle. Arbor
adapters mount face mills on the spindle. Collet adapters mount end mills on
the spindle. Taper-shank end mills mount in adapters that have holes with
matching tapers. If the taper shank on the tool is smaller than the hole in the
adapter, put a reducing sleeve into the adapter. Shell end mill adapters come
in different sizes to accept different-sized shell end mills.
17:4 End mill holders also receive
straight-shanked end mills.
To remove arbors or adapters held with a drawbar, follow these steps:
* Loosen the locknut on the drawbar about two turns.
* Hit the end of the drawbar with a dead blow hammer, releasing the arbor or adapter from the
spindle hole.
* Hold the arbor or adapter so it won’t fall out of the spindle when the drawbar is removed.
* Unscrew the drawbar and remove the arbor or adapter.
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MBmiliy. Midas 1720 Manual
Your machine includes a tapered drift for removing tapers. Follow these steps:
* Remove the drawbar.
* Extend the mill spindle to expose the outer taper drift slot.
* Rotate the spindle to align outer and inner taper drift slots. You will be able to see the end of the
adapter through both slots.
* Insert the drift in the slot.
* Holding the adapter with one hand, use a nonmarring hammer (rubber, dead-blow, or brass) to
drive the drift into the slot. The taper on the tool will release and the adapter drop out.
Cutters mounted in the spindle must fit accurately. There are two ways to make sure they do. For
small cutters, fit the shank of the arbor that carries the cutter directly into the taper hole at the end of
the spindle. A drawbar holds the arbor in place. For large cutters, bolt the cutter directly to the end of
the spindle.
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BSmithy. Midas 1720 Manual
17:2 Miling Cutters (
Choose milling cutters for the type of cut, the number of parts, and the material. Rake angles depend
on both cutter and work material. Clearance angles range from 3° to 6° for hard or tough materials to
6° to 12° for soft materials.
To determine the number of teeth you want, consider the following:
* There should not be so many teeth that they reduce the free flow of chips.
* The chip space should be smooth so chips don’t clog.
* Don’t engage more than two teeth at a time in the cut.
End Mill Cutters
17:5 Two-flute end mills have two
End mill cutters cut on their ends and sides. They are either solid (cut from teeth that cut to the center of the
a single piece of material) or shell (separate cutter body and shank). They mill.
have two, three, four, or more teeth and may do right or left-handed cutting.
Their flute twist or helix may also be right or left-handed. Solid end mills have straight or tapered
shanks; shell end mill adapters have tapered shanks.
End mills machine horizontal, vertical, angular, or irregular surfaces in making slots, keyways, (
pockets, shoulders, and flat surfaces.
* Two-flute, or center-cutting, end mills (Figure 17:5) have two teeth that cut to the center of the
mill. They may feed into the work like a drill (called plunge milling), then go lengthwise to form a slot.
Teeth may be on one end (single-ended) or both ends (double-ended).
* Multiple-flute end mills have three, four, six, or eight flutes and may be
single or double-ended. Multiple-flute mills are center-cutting or noncenter-
cutting. Don’t use noncenter-cutting end mills for plunge milling.
* Geometry-forming end mills form particular geometries. They include
ball end mills, roughing end mills, dovetail end mills, T-slot cutters, keyseat
cutters, and shell end mills.
Ball end mills (Figure 17:7) cut slots or fillets with a radius bottom, round
out pockets and bottoms of holes, and do diesinking and diemaking. Four-
fluted ball end mills with center cutting lips are available. fro Bal en amills Cut slots or
Roughing end mills remove large amounts of metal rapidly with minimum
horsepower. They have three to eight flutes. Also called hogging end mills, they have wavy teeth on
their periphery that pro-vide many cutting edges, minimizing chatter.
T-slot cutters cut T-slots. After machining a groove for the narrow part of the T-slot with an end or
side mill, finish up with the T-slot cutter.
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MBmitiy. Midas 1720 Manual
Page 58
Keyseat cutters cut keyseats for Woodruff keys (shaped like a half circle).
Shell end mills (Figure 17:7), which mill wide, flat surfaces, have a hole for mounting on a short
arbor. The center of the shell is recessed to provide space for the screw or nut that fastens the cutter to
the arbor. The teeth are usually helical, and diameters are as large as 6".
Insert-type end mills use replaceable HSS or carbide inserts. Small
end mills use two inserts; larger end mills, three or more.
Face milling cutters start in size at 2" and have inserted teeth on the
periphery and face. Most of the cutting takes place on the periphery.
They are similar to, but larger than, shell end mills.
Plain milling cutters
17:7 Shell end milts mill wide,
Plain milling cutters have teeth only on their periphery. Used to mill flat surfaces and mount on
plain, flat surfaces, they may combine with other cutters to produce arbors.
various shapes. They are cylindrical and come in many widths and
diameters.
* Light-duty plain cutters for light cuts and fine feeds come in two forms. Narrow ones have
straight teeth parallel to the cutter axis. Wide ones have helical teeth at a 25° angle. Features include
ease of starting cuts, little chatter, and good surface finishes.
* Heavy-duty plain cutters, or coarse-tooth cutters, come in larger widths and have larger and fewer
teeth. Strongly supported cutting edges and wide flutes provide strength and space for heavy chip
removal. The helix angle of their teeth is 25° to 45°.
* Helical plain milling cutters have even fewer and coarser teeth with a helix angle of 45-60” or
greater. These cutters are for wide, shallow profiling cuts on brass or soft steel.
Side milling cutters
Similar to plain milling cutters, side milling cutters also have teeth on
one or both sides (Figure 17:8). The teeth on the periphery do most of
the cutting; those on the sides finish the side of the cut to size. They cut
grooves or slots and often work with other cutters to mill special shapes
in one operation.
* Plain side milling cutters have straight teeth on the periphery and
both sides. Side teeth taper toward the center of the cutter, giving side 17:8 Side milling cutters are sim-
. ilar to plain milling cutter, but they
relief or clearance. have teeth on one or both sides.
* Half side milling cutters have helical teeth on the periphery and
one side. These cutters do heavy-duty face milling and straddle milling where teeth are needed on only
one side. The side teeth are deeper and longer for more chip clearance.
* Staggered-tooth side milling cutters are narrow cutters with teeth alternating on opposite sides.
There is less dragging and scoring and more space for chip removal. These cutters do heavy-duty
keyway and slotting cuts.
MSmbiry. Midas 1720 Manual
Slitting saws
Slitting saws do narrow slotting and cut-off operations.
* Plain slitting saws are thin, plain milling cutters with only
peripheral teeth. The teeth are fine, and the sides taper slightly
toward the hole, giving side relief.
* Slitting saws with side teeth are like side milling cutters and are
for deeper slotting and cut-off operations normally done with plain
slitting saws.
17:9 Flycutters take light face
cuts from large surface areas.
* Staggered-tooth slitting saws have peripheral teeth with alternate right and left-hand helix and
alternate side teeth. They are for 0.2" and wider cuts and may do deeper cuts with standard feeds.
* Screw-slotting cutters are plain slitting saws with fine-pitch teeth that cut slots in screwheads.
Their sides are straight and parallel and offer no side relief.
Angle milling cutters
Angle milling cutters, for such operations as cutting V-grooves, dovetails, and reamer teeth, come as
single and double-angle cutters.
* Single-angle cutters have one angular surface. Teeth are on the angular surface and the straight |
side, and they usually have 45° or 60° angles. |
* Double-angle cutters machine V-grooves. Those with equal angles on both faces usually have an
included angle of 45°, 60°,
or 90°.
Form-relieved cutters
Formed-tooth cutters machine surfaces with curved outlines. You can sharpen them without changing
the tooth outline. Concave cutters mill convex half-circles; convex cutters cut concave surfaces.
Corner-rounding cutters round outside corners. Gear cutters cut gear teeth. Fluting cutters cut
flutes in reamers and milling cutters. Formed-tooth cutters come in right and left-hand styles and
various special shapes.
Flycutters
With one or more single-point toolbits or cutters, flycutters (Figure 17:9) perform end milling even
though they’re not end mills. They take light face cuts from large surface areas. You must grind the
toolbit properly to get correct rake and clearance angles. Grind toolbits for flycutters as you grind lathe
tools (Section Seven).
You can also use flycutters for boring. Note: When the tool revolves, the cutting tool becomes
almost invisible, so be careful.
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17:3 Using cutting fluid
Cutting fluids get rid of heat generated by the friction of the milling cutter against the workpiece. They
also lubricate the interface between the cutting edge and the workpiece and flush chips away. You can
apply fluid in a stream (flood) or as a mist.
We recommend cutting fluids for steel, aluminum, and copper alloys. With cast iron and steel,
however, they tend to reduce the life of carbide tools, leaving tiny cracks along the cutting edge.
Follow the advice of tool manufacturers to avoid tool failure. Materials such as cast iron, brass, and
plastics are often machined dry. You can use compressed air to cool tools and clear chips away. When
doing so, wear a face mask and protective clothing (Figure 20.6), and be careful to keep cast-iron dust
from getting between the lathe and carriage ways.
17:4 Tool grinding
Sharpen cutting tools when they become dull, or extreme forces may build up at the cutting edge of the
teeth, causing chipping or fracture. Dull cutters are also inefficient, and regrinding very dull cutters
shortens their life considerably.
The form of the cutting edge and the clearance back of the cutting edge (land) affect cutter opera-
tion significantly. The angle formed by the land and a line tangent to the cutter at the tooth tip is the
primary clearance. The angle between the back of the land and the heel of the tooth is the secondary
clearance. Check both clearances and the rake.
Some cutters are sharpened on the periphery by grinding the land at a suitable angle. They include
cutters with straight or spiral teeth, angular cutters, side milling cutters, face mills, end mills, and
reamers.
You sharpen others by grinding the front faces of their teeth. Formed or relieved cutters, for ex-
ample, have profiles that must be preserved. This category includes all sorts of formed cutters as well
as cutters used for milling various regular and irregular shapes.
BSmithy. Midas 1720 Manual
17:5 Speeds and Feeds for Millling
Milling cutting rates vary according to the machinability of the material being cut; whether cutting
fluid is used and, if so, what kind; the type, size, and material of the cutter and the coarseness of its
teeth; and the amount of metal being removed. Cutting speed for milling is the distance the cutting
edge of a tooth travels in one minute. If cutting speed is too high, the cutter overheats and dulls. If it's
too low, production is inefficient and rough.
There is no exact right cutting speed for milling a particular material (Figure 21.1). Machinists
usually start with an average speed, then increase or decrease it as appropriate. For light cuts, use the
upper end. Use the lower end for heavy cuts and when you don’t use cutting fluid.
Determining rpm. To set the spindle speed, you have to know the cutter rpm (revolutions per
minute). For inch measurement, use the following formula:
rpm = 12 x CS (fpm) / D” x x
where CS = cutting speed, fpm = feet per minute, D” = diameter of the cutter in inches, and x = 3.14.
For metric measurement, use this formula:
rpm = CS (mpm) x 1000 / D (mm) x x
where CS = cutting speed, mpm = meters per minute, D (mm) = diameter of the cutter in millimeters,
and x = 3.14. You can use an rpm chart for selected diameters of cutting tools at different cutting |
speeds.
To change speeds, set the belts according to Figure 5.3.
Feeds
Set the direction of feed before you begin milling. Up milling, or conventional milling, is when the
direction of feed is opposite to the direction of cutter rotation. Down milling, or climb milling, is
when the direction of feed is the same as the direction of cutter rotation.
Up milling. In up milling, forces on the workpiece tend to pull it out of the vise or fixture holding
it, so fasten it securely. These forces also push the workpiece away from the cutter, which eliminates
backlash. Up milling is advised for milling cast iron, softer steels, and other ductile materials. In
general, it's how you should perform milling operations.
Down milling. Down milling usually produces good surface finishes because chips do not sweep
back into the cut. Setups are more rigid, an advantage when cutting thin workpieces held in a vise or
workpieces held in a magnetic chuck. Down milling also produces straighter cuts. We recommend
down milling when using carbide cutters because there is less wear on the cutting tool. In general,
however, avoid it because of the backlash problems associated with it.
Feed rates. Your feed rate should be as high as your machine, cutting tool, workholding method,
and workpiece can tolerate while giving a good finish. Feed rate is usually given in inches per minute
Page 61
BSmithy. Midas 1720 Manual
Page 62
17.10 Recommended Cutting Speeds for Milling (fpm)
Material
Brinell High-Speed-Steel | Carbide
Hardness Cutters Cutters
Free-machining low-carbon 1111 100-150 120-160 400-600
steel resulphurized 1112 150-200 120-180 400-900
Free-machining low-carbon — 10L18 100-150 100-225 250-500
steel leaded 12L14 150-220 110-250 250-600
Plain low-carbon steels 1006 100-125 80-150 300-600
1026 125-175 80-140 250-500
Plain medium-carbon steels 1030 125-175 80-140 250-500
1095 175-225 60-110 225-400
Plain high-carbon steels 1060 125-175 70-120 250-450
1095 175-225 60-110 225-400
Tool steels Wi-W7 150-200 80-120 300-350
H20-H43 200-250 40-85 175-300
D1-D7 200-250 30-60 100-200
Stainless steel 302 135-185 70-100 225-350
430F 135-185 100-140 350-450
Gray cast iron ASTM class 20
Through scale 110-160 140-200 350-700
Under scale 130-225 400-800
Aluminum Cold-drawn
wrought alloys 500-800 1000-1800
Aluminum Casting alloy
(as cast) 600-1000 1200-2000
Brass 360 free-cutting,
cold-drawn 300-500 600-1000
Bronze 220 commercial
annealed 80-140 180-275
Feed direction
—— — — >
Feed direction
Down
milling
17:4 In up milling (left), the workpiece feeds into the cutter in the opposite
direction of the cutter's revolutions. In down milling (right), the workpiece
feeds into the cutter in the same direction as the cutter is turning.
BSauktiey. Midas 1720 Manual
(ipm). You determine feed rate by the speed of the cutter in rpm and the number of teeth in the cutter. (
There are many factors to consider in selecting the feed per tooth, and there is no easy formula to
follow. Here are several principles to guide you:
* Use the highest feed rate conditions allow
* Avoid using a feed rate below 0.001" per tooth
‘* Harder materials require lower feed rates than softer materials
* Feed wider, deeper cuts more slowly than narrow, shallow cuts
* Slower feed rates gives a better surface finish
* Never stop the feed before finishing the cut.
If you know the feed in inches per tooth, use this formula to calculate table feed rate in inches per
minute (ipm): |
ipm = ipt 5 N 5 rpm
where ipt = inches per tooth, N = number of teeth in the milling cutter, and rpm = spindle speed of the {
milling machine.
Page 63
®Smithy. Midas 1720 Manual
Page 64
17:6 Common milling operations
Milling flat surfaces
One way to mill a flat surface is by plane milling (Figure 17.11).
Adjust the milling cutter vertically to give the needed depth of
cut while the workpiece is held on the table and slowly feed it
horizontally. Every tooth on the periphery of the cutter removes
a chip every revolution. Milling wide, flat surfaces this way is
called slab milling.
Another way to mill flat surfaces is by face milling. In this
method, the cutter teeth operate at right angles to the cutter axis. [J tA a
Inserted-tooth face-milling cutters (Figure 17:12) face-mill large 17.11 One way to mill a flat surface is by
surfaces. plane milling.
Bevels and chamfers are cut at an angle to the main work-piece
surface. A bevel cut (Figure 17.13) goes from side to side, completely
removing the perpendicular edge. A chamfer removes only part of the
perpendicular edge.
To cut bevels and chamfers, either move the workpiece into an
angular cutter or hold the workpiece at the desired angle while moving
it into a plain cutter or end mill. You may hold the workpiece in a vise or
in a fixture held in a vise.
Squaring a workpiece 17:12 Inserted-tooth face-
milling cutters face-mill large
To square the ends of a workpiece, use the peripheral teeth of an end surfaces.
mill. If you want to remove a lot of material, use a roughing end mill
first, then finish to size with a regular end mill.
Plunge cutting is efficient for removing material quickly on low horsepower. Plunge the end mill
a predetermined width and depth, retract it, then advance and plunge it again repeatedly. The maxi-
mum cutting force is in the machine’s strongest (axial) direction.
Milling a cavity
After laying out the outline of the cavity to cut, rough it out to
within 0.030" of the finished size before making finish cuts. Use a
center-cutting end mill for the starting hole.
Tapping
Drill a hole. Then remove the drill bit and put a tap into the chuck.
By turning the chuck slowly by hand with slight downward pres-
sure, you can get a perfectly threaded hole.
17.13 Abevel cut goes from side t
side, completely removing the
perpendicular edge.
BSmithy. Midas 1720 Manual
SECTION EIGHTEEN
WORKHOLDING
The most common ways to hold a workpiece during milling are to secure it directly to the table via clamps or
hold it in a vise (Figure 18.1). If you're making many similar workpieces, you may make a special fixture to
hold them. Whatever method you use, hold the workpiece securely so it won’t shift during machining and
support it adequately to avoid swing.
18.1 Mounting to the table
If you need to align the workpiece to the table, place it against stops that exactly fit the table’s T-slots. Another
way 1s to measure in from the edge of the table to the workpiece. Be sure the table and workpiece are clean and
free of burrs. Another method is to use the face of the spindle plate, chuck or taistock as a quick reference
surface.
18.2 Using a vise
Vise sizes are designated by the width of the vise jaw in inches or millimeters. Plain and swivel vises range.
from 3 to 10" (76 to 254 mm). Tilting and universal vises range from 3—4" to 5" (76-102 mm to 127 mm).
The bases of many vises are fitted with keys—small steel blocks that fit into the milling table T-slot for
quick alignment of the vise. Before mounting a vise, make sure the bottom is clean and smooth. If there are any ,
nicks or burrs, remove them with a honing stone. Set up the workpiece securely and correctly, and fasten the
vise tightly to the table.
Plain vises have a flanged base with slots that lets them bolt to the table with the jaw faces either parallel
to, or at 90° to, the longitudinal table travel. Swivel vises have a swivel base that bolts to the table. They're
marked with degree graduations that let you position their jaws at any angle without moving the base. Universal
vises tilt up or sideways, or swivel. They hold workpieces machined at a double or compound angle. Tilting
vises are like universal vises except they do not tilt sideways.
Using special fixtures. Clamp both workpiece and fixture securely in place. Be sure they are clean.
Watch them carefully during machining; a loose fixture or workpiece can be disastrous.
18.3 Dividing heads
Also called indexing heads, dividing heads attach to the table to hold workpieces between centers for machining
surfaces, grooves, or gear teeth at precise distances apart.
The main parts of a dividing head are its head and tailstock. The tailstock holds the outer end of the
workpiece. The head is more complex. When you turn its handle, a spindle rotates through a precisely machined
gearing system. A chuck can attach to the spindle face, which is set at 90° to the handle (Figure 18.2). An
indexing plate is set in from the handle. By counting how many turns of the handle it takes to turn the workpiece
a certain number of degrees, you can make cuts at different angles. This is how to cut gears. |
Page 65
BSmithy. Midas 1720 Manual
Page 66
18.4 Rotary tables
A rotary table (Figure 18.3) is a precision worm and wheel unit that lets
you cut gears, precision holes, and curved slots. Rotary tables mount
vertically or horizontally to the table. T-slots secure the workpiece. A
typical rotary table is graduated in degrees and fractions.
18.3 Rotary tables let you cut
gears, precision holes, and
The index plate on the rotary table has several circles of equally curved slots.
spaced holes into which the index crankpin fits. Although the hole
circles are spaced equally, the number of holes varies in different circles,
so you can get many different numbers of circumference divisions. You can buy sets of index plates for
even more circumference divisions. Contact a Smithy technician for more information.
DSmithy. Midas 1720 Manual
SECTION NINETEEN
TROUBLESHOOTING
19.1 Powerfeed and thread cutting
Powerfeed does not move carriage
Cause
* Carriage locked
* Speed selector not engaged
* Leadscrew lever not engaged
* Gears not meshing or teeth missing
* Half-nut fully engaged
* Sheard Pin on left enf of leadscrew
Cut is not smooth
Cause
* Tool dull
* Tool not on center
* Tools not mounted tightly in post
* Cross-slide gibs to bed and base loose
* Gibs in toolpost loose
* Tool turret not tight
* Feed rate too fast
* Gears loose
Thread is not smooth
Cause
* Tool dull
* Tool not centered
* Tools not mounted tight in post
* Cross-slide gibs to bed and base loose
* Gibs in compound loose
* Tool turret not tight
* Gears loose
Tool is not cutting “on thread”
Cause
* Half nut not engaged at proper time
Solution
Unlock carriage
Select speed I or II or III
Move lever to the left
Check gears and mesh
Keep half nut engaged
Replace Pin
Solution
Sharpen or replace tool
Center tool (shim, if needed)
Remount tools *
Adjust gibs |
Adjust gibs in toolpost
Tighten toolpost
Install correct gears
Tighten gears and posts
Solution
Sharpen tool
Center tool
Remount tools
Adjust gibs
Adjust gibs
Tighten toolpost
Tighten gears and posts
Solution
Check chart (Figure 16.6)
Page 67
Simbiry. Midas 1720 Manual
19.2 Carriage/milling table
Powerfeed doen't move table
Cause
e Carriage
* Speed Selector not engaged
* Leadscrew lever not engaged
* Gear not meshing or teeth missing
Horizontal movement in cross-slide table
Cause
* Carriage gib improperly adjusted
* Table gib improperly adjusted
Vertical movement in cross-slide table
Cause
* Carriage gib improperly adjusted
* Table gib improperly adjusted
Carriage moves smoothly in only one direction
Cause
* Debris on way or gib
* Burr on gib
* Gib improperly tensioned
Solution
Unlock Carriage
Select Speed I, II or III
Move lever to the left
Check and adjsut gears
Solution
Adjust carriage gib
Adjust table gib
Solution
Adjust carriage gib
Adjust table gib
Solution
Remove debris
Remove burr with fine file
Loosen gib and re-tension
Cross-slide handivheel turns during cutting operations
Cause
e Cross-slide nut worn
* Carriage locks not tight
e Gibs too loose
Too much backlash in the cross slide
Cause
* Loose screw holding crossfeed nut
® Worn brass nut
* Loose spanner nuts
Page 68
Solution
Replace brass nut
Tighten carriage locks
Readjust gibs
Solution
Tighten screw,
Replace nut
Adjsut Spanner Nuts
19.3 Lathe turning
Cut is rough
Cause
* Tool dull
* Tool not ground properly
* Tool at wrong angle
* Tools not held tightly
* Wrong cutter for material
* Cutting speed incorrect
Work has unwanted taper
Cause
* Work improperly aligned
* Debris in spindle, setup, or tools
* Offset tailstock incorrectly positioned
* Spindle out of alignment
Machine vibrates
Cause
* Work mounted wrong
* Speed too high
* Too much pressure at tailstock
Work stops turning but machine continues to run
Cause
* Work not mounted securely
* Tools forced into work
* Belts slipping
Diameter of work is not consistent
Cause
* Too much flex in workpiece
* Too much flex in compoun rest,
crosslide, or carriage
Mámbiy. Midas 1720 Manual
Solution
Sharpen or replace tool
Regrind tool
Correct tool position
Tighten toolholder
Use correct cutter
Increase or reduce speed
Solution
Realign centers on work
Clean and reset setup, work, or tool
Correct position of tailstock
Tighten taper bearings to return to
alignment, replace spindle bearings
Solution
Remount work
Reduce speed
Reduce pressure and increase
lubrication
Solution
Remount work
Reduce force on tools
Tension belts, use belt dressing, or
replace belts
Solution
Use a follow rest
Tighten gibs, clean ways
Page 69
@fmitiy. Midas 1720 Manual
Too much backlash in compound
Cause Solution
* Loose spanner nuts Tighten Spanner Nuts
* Worn nut Replace nut
Machine slings oil from behind the chuck or in belt box
Cause Solution
e Oil reservoir overfilled Check oil level
* Worn oil seal Replacefelt in seal
19.4 Milling
Tool chatters
Cause Solution
* Gibs too loole on cross slide, cnpoung Readjsut Gibs
Or carriage
® Unused feeds nto locked Lock all axes but the one moving
* Milhead not locked Lock millhead
* Quill too loose Tighten guill lock
* Tool not on center Center Tool
* Improper tool shape, too dull Reshape, sharpen, or replace tool
Deph of cut is not consistent
Cause Solution
* Quill moving Lock Quill
e Setup Wrong Make sure setup is parallel to table
19.5 Drilling
Hole is off center or bit wandres
Cause Solution
* Bit Dull Use Sharp Bit
* Bit not mounted correctly in check Remount Tool
* Bit Bent Replace Bit
*C huck loose in spindle Remount chuck and arbor and remount
* Drawbar not secured Tighten Drawbar
* Debris on Spindle Clean debris and arbor and remounmt tool
Page 70
* Bit bent
* Chuck loose in spindle
* Drawbar not secured
* Debris on spindle
* Bearings loose or worn
* Cutting too fast
* Incorrect bit
Entrance hole is out of round
Cause
e Bit dull
® Incorrect drill bit
Bit turns erratically or stops
Cause
* Bit fed into work too fast
® Belts slipping
Chuck is difficult to tighten or loosen
Cause
* Chuck sticking
¢ Debris in chuck
Chuck wobbles
Cause
e Chuck loose on arbor
* Drawbar not tight
19.6 Drive system
Turn on machine and nothing happens
Cause
* End Door Open
* Machine unplugged
* Loose electrical connections
@Smlthy. Midas 1720 Manual
Replace bit
Remount chuck on arbor
Tighten drawbar (
Clean debris and arbor and remount |
tool
Tighten or replace bearings
Reduce speed
Use correct bit
Solution
Use sharp bit
Use correct bit
Solution
Reduce feed rate
Reduce feed rate, re-tension belts
Solution
Apply lubricant
Clean chuck
Solution
Clean arbor and remount
Clean spindle and replace drawbar
Solution
Close and latch door
Plug in machine
Tighten wiring connections
Page 71
Smithy. Midas 1720 Manual
Page 72
SECTION TWENTY
PARTS LISTS WITH SCHEMATICS
Diagram 1:0
Diagram 2:0
Diagram 3:0
Diagram 4:0
Diagram 5:0
5:1
5:2
Diagram 6:0
Diagram 7:0
Diagram 8:0
8:1
8:2
Diagram 9:0
Diagaram 10:0
Diagram 11:0
Diagram 12:0
Diagram 13:0
Diagarm 14:0
Lathe Bed and Tailstock
Headstock
Control Panel and Pulley Box
Lathe Idler Pulley
Millhead
Mill Quill and Spindle
Mill Idler Pulley
Mill Fine Feed/Drill Press
Crossfeed and Apron
CNC Mount (Y Axis)
CNC Mount (Z Axis)
CNC Mount (X Axis)
Tailstock
Threading Dial
Leadscrew Cover
Steady Rest
Follow Rest
Wiring Diagram
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