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Lathe Operations

Lathe OperationsNMS60C000102 Page 1

NMS60 Lathe Operations

08/05/2011


TABLE OF CONTENTS

Course Objectives............................................................................................................2

Lesson 1 Objectives.........................................................................................................2Lathe Safety ..........................................................................................................3Lathe Components...................................................................................................5Lathe Accessories....................................................................................................6Lathe Cutting Tools..................................................................................................8Cutting Speeds and Feeds........................................................................................9

Lesson 2 Objectives.......................................................................................................11Mounting and Aligning Lathe Centers.....................................................................12Facing Between Centers.........................................................................................12Machining Between Centers...................................................................................13Knurling, Grooving & Form Turning........................................................................16Turning Tapers .....................................................................................................17Cutting Threads.....................................................................................................19

Lesson 3 Objectives ..........................................................................................................21Machining in Three-Jaw Chuck....................................................................................22Machining in Four-Jaw Chuck .....................................................................................23Facing, Grooving and Cutting off Work in a Chuck.......................................................23Drilling Holes Using a Lathe........................................................................................24Reaming and Boring Using a Lathe.............................................................................24Tapping an Internal Thread Using a Lathe...................................................................25


COURSE TERMINAL OBJECTIVE

Given various machine operations on the lathe, the Maintenance Mechanic will describe how to safely and properly operate the lathe applying Palo

Verde standards and expectations. Mastery will be demonstrated by successfully completing a written examination with a score of 80% or

better.

LESSON TERMINAL OBJECTIVE

Given a Lathe machining operation, the Maintenance Mechanic will explain the basic safety rules for the operation of the lathe and identify the

component parts of the lathe. Mastery will be demonstrated by successfully completing a written examination with a score of 80% or better.

LESSON 1 ENABLING OBJECTIVES

EO01 State the basic safety precautions for using a lathe.

EO02 Describe the component parts of a lathe and their functions.

EO03 Describe the various lathe accessories and their functions.

EO04 Describe the types of lathe cutting tools.

EO05 Identify the methods of determining the proper cutting speeds, feeds, and depth of cut.


EO01 State the basic safety precautions for using a lathe.

LATHE SAFETY

General Shop Rules

1. No horseplay

2. Understand the lathe controls

3. Not understanding what will happen when a lever or switch is turned can be extremely dangerous. This is evident in the following event.

Plant: PickeringTitle: Machine Shop Accident on Lathe (Reference: SCR P-1998-01727)Summary: A Mechanical Maintainer assigned to a "Machining for Fitters" course was polishing the surface finish of a project he was completing. The project was a fireplace poker approximately 24 inches in length with a composite material laminated handle. After polishing the handle he noticed chuck marks on the ½-inch diameter shaft and decided to polish the shaft to remove the marks. The piece was re -chucked with approximately 19 inches extending from the chuck unsupported. The lathe was started with a speed of 840 RPM but the Maintainer decided that he should increase the speed to 1500 RPM to improve the polishing process. Following speed adjustment, the lathe was restarted and immediately the project piece became unbalanced and bent at approximately 45 degrees striking the Maintainer in the chest and jamming itself against the lathe bedway. The shaft began slipping in the jaws of the chuck producing a loud noise, which alerted the instructor who switched off the lathe.

4. Be sure that you can stop the machine immediately. Conduct Two Minute Drill to familiarize yourself with lathe controls.

Safety Guards-Do not operate the machine unless the safety guards are installed properly. Be sure to stop the lathe when you are measuring work or cleaning, lubricating or adjusting the machine.

When cleaning your work, do not use a rag to clean work in a lathe while the machine is operating.

Stopping the lathe-never attempt to stop a coasting lathe by hand as there are many projections (drive plate or chuck) that will injure your hand seriously.

Mounted work-Ensure that the chuck or faceplate is mounted securely before starting the lathe. If an accessory comes off the machine during operation it will act like a missile.


Keep these following rules in mind regarding the Chuck Wrench:

Ensure the chuck wrench is removed from the chuck prior to starting the lathe.

Keep your hand on the chuck wrench at all times when it is in the chuck.

If the wrench were in the chuck when the lathe was started it could either fly off like a missile or jam between the chuck and lathe bed damaging the chuck, lathe bed, spindle and wrench.

Take the following action prior to starting the Lathe. Move the carriage to the furthest position of the cut to ensure that the tool will not incidentally contact the work. Also, turn the spindle by hand one complete revolution

to ensure there are no obstructions.

When working around a stopped lathe remove the tool bit to prevent serious cuts to hands and arms.

LATHE DESCRIPTION

It operates on the basic principle of the work being held and rotated on its axis while the cutting tool is stationary and advanced along the lines of a desired cut.

Lathe Size and Capacity is determined by the largest work diameter that can be swung over the lathe ways and generally the maximum distance between centers.


EO02 Describe the component parts of a lathe and their functions

Typical Lathe (page 350)

Component parts of a lathe

Bed- Top section is the machined ways and is used to guide and align the major parts of a lathe.

Headstock is clamped on the left side of lathe bed. The headstock spindle is a hollow, cylindrical shaft supported by bearings and provides drive from motor to work-holding devices such as live center, faceplate, or chuck. It is driven by belt and pulley or gearbox.

The Quick change gearbox provides feed rod and lead screw with various rates of feeds.

Half-nut or Split-nut lever has synchronous engagement for thread cutting.

The Carriage consists of the saddle, crosslide and apron.

The Tailstock provides support for the right end of work and contains the Tailstock spindle, which has an internal taper.

Lathe Care and Maintenance

Clean the lathe after each use. Lubricate the lathe by applying a coat of oil on ways and other sliding surfaces and grease in grease fittings. Cover ways with paper when filing, grinding, or polishing to prevent abrasives or fine particles from damaging precision surfaces. Do not over tighten clamps as this can cause undue wear on components. Use proper wrenches for adjustments that must be made. Ensure spindle is stopped before changing gears. Trying to change gears while the spindle is still spinning may result in damage to the gearbox. Check oil reservoirs for proper levels and fill as needed. Machine must be level to ensure that the lathe runs true. Do not abuse machine by hammering or forcing mechanisms.


EO03 Describe the various lathe accessories and their functions


Lathe Accessories (page 358)

Work holding, supporting, and driving devices include the following:

Centers- 60 degree with Morse taper shank and they require periodic lubrication.

Revolving dead center (Live Center) - No lubricant needed as they have sealed bearings.

Microset adjustment. (these are for O.D. grinders) - Permit limited amount of adjustment to each side of center.

Self-driving live center has grooves to provide drive and is used in head stock to enable a continuous cut.

Chucks

Three-jaw Universal chuck is used for holding round or hexagonal shaped stock. It grasps the work quickly within a few thousandths of an inch.

Four-Jaw Independent chuck can be used to hold round, square, hexagonal and irregular-shaped workpieces.

Spindle Noses may be: Threaded-Clockwise, Tapered- which uses a Lock Ring, and the Cam-lock spindle nose.

Spring collet chucks are accurate but have a limited range.

Jacobs Chuck uses Rubber-Flex collets which gives it the ability to hold a wider range of work diameters.

Magnetic chucks are for light cuts only.

Faceplates have slots for bolts to secure a workpiece that is too large of such a shape that it cannot be held in a chuck or between centers.

Steadyrest - supports long work. (see picture at right)

Follower rest - prevents work springing away and is mounted on carriage.

Mandrels are used to hold internally machined workpieces between centers.

The following Lathe Dogs may be used to drive work that is being machined between centers.

Standard bent-tail dog is the most commonly used dog for round workpieces.

Straight-tail dog is driven by a stud in the drive plate and is used in precision turning.


Safety-clamp dog is useful where you don’t want the work marred by the setscrew of the other dogs.

Clamp dog is the most versatile of the dogs and is best for odd-shaped workpieces.

Cutting Tool Holding Devices (page 364)

Tool Holders

Right -hand offset used for machining close to chuck - right to left

Left -hand offset is used for machining close to tailstock - left to right and facing.

Straight is for general machining operations.

Carbide Toolholder holds tool bit so that there is little or no back rake.

Cut-off (Parting) used when work needs to be grooved or parted.

Boring Bars are held by tool holders that fit the Aloris tool post.

Tool Posts- Primarily we use Aloris tool posts here at Palo Verde and are of the Quick-change/Dovetailed variety.

Turret-type holds more than one tool at a time.


EO04 Describe the types of lathe cutting tools

LATHE CUTTING TOOLS

Lathe toolbits are generally made of four materials.

High speed steel

Cast alloys (stellite) (replaced by carbides)

Cemented carbides and Ceramics

Lathe toolbits should possess the following properties: they should be hard, wear-resistant, withstand high temperatures and withstand shock.

Cutting Tool Nomenclature (page 213)

Base is the bottom of the tool shank. Cutting edge is the leading edge of the toolbit that does the cutting. The face is the surface against which the chip bears as it is separated from the work and the flank is the surface of the tool which is adjacent to and below the cutting edge. The nose is the tip of the cutting tool formed by the junction of the cutting edge and the front face. The nose radius is the radius to which the nose is ground. Small radius is for rough cuts and a large radius is for finish cuts. The point is the end of the tool that has been ground for cutting purposes and the shank is the part of the toolbit that is held in the toolholder.

Toolbit Angles and Clearances (pages 214-215)

Side cutting edge angle is the angle that the cutting edge forms with the side of the tool shank. The end cutting edge angle is formed by the end of the cutting edge and a line at right angles to the centerline of the toolbit. The side relief angle (clearance) is the angle ground on the flank of the tool below the cutting edge. The end relief angle (clearance), which is ground below the nose of the toolbit, permits the cutting tool to be fed into the work. Side rake angle is the angle at which the face is ground away from the cutting edge. The back (top) rake is the backward slope on the top of the toolbit and helps chips to escape easily and makes the tool cut better.

Grinding a General-Purpose Toolbit

Dress the face of the grinding wheel prior to grinding toolbit. Grip toolbit firmly and support hands on the grinder. Grind the side cutting edge angle and the side relief angle. Keep the toolbit moving across the grinding wheel as this speeds the grinding process and prevents grooving of the grinding wheel. Keep the toolbit cool. Grind end cutting edge and end relief angle. Grind side rake and nose radius. Hone cutting edge slightly as this will extend the life of the toolbit.


EO05 Identify the methods of determining the proper cutting speeds, feeds, and depth of cut

CUTTING SPEEDS AND FEEDS

Speeds - The rate at which a point on the work circumference passes the cutting tool. These are expressed in Feet per minute.

Converted to RPM to adjust machine.

This is not convenientRPM = CS X 12 DORThis is convenientRPM = CS X 4 D

Feed - The distance a cutting tool advances for each revolution of the workpiece.

Roughing cut - Coarse Feed

Finishing cut - Fine Feed

General Guidelines:

Speed and feed are inversely related

Lower speeds for harder materials

Higher speeds for harder toolbit materials

Lower speeds for roughing cuts

Higher speeds for finishing cuts

Lower speeds for long cutting edges

Lower speeds for castings

Cutting fluids serve the following purposes:


Cools the toolbit and work

Lubricates chip bearing surface of toolbit

Better surface finish

Aids removal of chips

Protects equipment

Protects operator from dust

Cutting fluids may be of the following types:

Soluble oil and water emulsions

Straight cutting oils

Chemical cutting oils(Synthetics)


LESSON 2 TERMINAL OBJECTIVE

Given the lathe operation of “machining between centers”, the Maintenance Mechanic will describe the various methods used and tooling required to

safely and properly operate the lathe machining between centers.


EO01 Describe the methods of mounting and aligning lathe centers

EO02 Describe the process of facing between centers

EO03 Describe the various processes of machining between centers

EO04 Describe the processes of knurling, grooving, and form turning on a lathe

EO05 Describe the process of turning tapers on a lathe

EO06 Describe the processes of thread cutting on a lathe


EO01 Describe the methods of mounting and aligning lathe centers

MACHINING BETWEEN CENTERS

Work is generally turned for some portion of its length then reversed. Live centers must run absolutely true.

When mounting lathe centers, inspect and remove any burrs and thoroughly clean tapers and centers. Do not attempt to clean taper while machine is running. Partially insert center in lathe spindle then force center in taper with quick snap.

This is the same method for tailstock (dead) center.

Check live (headstock) center for trueness with a dial indicator.

Removing centers

A knockout bar that is pushed trough the headstock spindle is used to remove a live center. The Tailstock (dead) center is removed by backing the handwheel of the tailstock.

Alignment of Centers can be accomplished by aligning the centerlines on tailstock with each other. This is only a visual check and not too accurate. The trial cut method, where a small cut is taken from each end of the work and the diameters are measured with a micrometer is more accurate but takes longer. Using a parallel test bar and dial indicator is the fastest and most accurate.

EO02 Describe the process of facing between centers

FACING BETWEEN CENTERS

Work mounted between centers can be machined, removed and re-set up while maintaining accuracy. When setting up toolbit, move toolpost to left side of compound rest. Set the cutting tool point to center of live center and tighten toolpost securely.

When mounting work, check live center for trueness and clean center points and tapers. Adjust tailstock to project 2-1/2 to 3 ". Loosen the tailstock clamp.

Fit lathe dog on left-hand end of work and leave it loose. Apply suitable center (high pressure grease) lubricant to right-hand end of the work. Place the lathe dog in the drive/face plate slot and slide the tailstock up to the other end. Tighten tailstock clamp. Adjust lathe dog and tighten setscrew. Turn drive plate by hand to check clearance. With tail of dog in slot, tighten tailstock handwheel and tighten tailstock spindle handwheel/ lever. Check the center tension. The part should rotate easily by hand in the drive dog slot. Turn lathe by hand to check clearance.

Facing Operation


The purposes of facing are:

Provides true, flat surface, square with work axis

Provides accurate surface from which to take measurements

Cut work to required length

A. Process

With the toolpost to left side of compound rest, set right-hand toolbit height to point of lathe center. Clean centers and tapers and mount work between centers. Set facing toolbit pointing left. Set lathe to the correct speed. Start lathe and bring toolbit as close to center as possible. Move carriage to left until toolbit just touches the work. Feed with crossfeed handwheel - cut from inside out. Continue this until cut is complete.

EO03 Describe the various processes of machining between centers

MACHINING OPERATIONS BETWEEN CENTERS

Parallel turning in a lathe is done for two reasons: to cut work to size and to produce a true diameter. The minimum number of cuts should be two (2). Roughing cuts may be (0.020" - 0.030") and finishing cuts may be (0.003" - 0.005"). The setting of the depth of cut should be done after a trial cut has been taken to establish exactly how much needs to be removed.

Move toolpost to left-hand side of compound rest and center toolbit. Tighten toolpost. Start lathe and take very light cut - .005" and true diameter for 1/4". Disengage the tool and back the cutting tool off the end of work. Stop the lathe and measure diameter and calculate the amount to be removed. Set graduated collar for the amount to be removed.

For rough turning, accuracy and surface finish not important and 0.020" to 0.030" cuts are recommended until diameter is taken to within .003" to .005" of final diameter.

Finish turning produces smooth surface and cut work to final diameter size.

Filing can be done after you turn your work to within .003" of final size. Cover lathe ways with paper. Mount work properly and move carriage out of the way. Disengage lead screw. Use mill or long angle lathe file and apply light pressure. Release pressure on return stroke. 30 - 40 strokes/minute is a common rate of filing. Too much pressure results in out of roundness. Clean file frequently and rub chalk or soap stone on file teeth to prevent clogging.


Polishing in Lathe

Using a piece of emery cloth a minimum of 12" long - 1" wide use 2 hands, one on each end of the emery cloth. In case it catches it will pull loose without pulling you into it. LET IT GO!


Plant: Fitzpatrick (USA): Injury Due to Lathe Accident (Reference: INPO OE9559) On November 21, 1998 at James A. Fitzpatrick, while performing polishing of a valve plug using a lathe, an individual’s glove/sleeve became entangled around the plug stem. The worker was pulled onto the lathe wrapping his arm around the stem causing severe personal injury. Co-workers secured the lathe, notified the Control Room, and assisted the individual by unwinding him from the lathe and making him comfortable until the Fire Brigade arrived.

Select type and grade of abrasive cloth depending on what you need to accomplish.

Aluminum oxide - ferrous metals

Silicon Carbide – nonferrous

Set the lathe at high speed and disengage lead screw. Remove toolpost and toolbit holder to reduce chance of injury. Lubricate center or use revolving center. Roll sleeves above the elbows and tuck in clothing. Start lathe and hold cloth on work. Don't allow long end to wind around the work. Move back and forth along the work until desired finish is obtained.

TURNING SHOULDERS

When turning more than one diameter on a piece of work, the change from one diameter to another is known as a shoulder.

Three types of shoulders:

Square

Filleted

Beveled

TURNING A SQUARE SHOULDER

Lay out shoulder position from finished end of the work. Position toolbit at this point and take a marking cut. With a turning tool, rough and finish to within 1/16". Set up end facing tool and chalk small diameter and just touch chalk mark with the toolbit.

*Note reading on graduated collar.

Face the shoulder square using hand feed and return to reading for successive cuts.

Machining a Filleted Shoulder

The purpose for a filleted shoulder is to strengthen the shoulder. Lay out length of shoulder with a center punch or marking cut. Rough and finish cut to length minus radius to be cut. Mount correct radius toolbit and set it to center. Lathe speed one-half of turning speed. Coat the small diameter near the shoulder with chalk or layout dye. Start the lathe and bring toolbit in to touch chalk. Feed cutting tool sideways with carriage handwheel until shoulder is cut.


MACHINING A BEVELED SHOULDER

Shoulders are beveled at angles from 30 to 60 degrees and the most common is 45 degrees. To make a beveled shoulder, turn large diameter to size and lay out position of shoulder along the length of the workpiece. Rough and finish cut the small diameter (minus the length of the bevel). Mount side cutting tool and set it to center of the lathe center point. Use a protractor and set tool to desired bevel angle. Chalk small diameter and set lathe speed one-half of normal cutting speed. Just touch the chalk and feed the carriage handwheel by hand. Apply cutting fluid and continue until bevel is correct size.

For large beveled angles, set compound rest to desired angle and install point cutting tool. Machine the bevel by feeding compound rest by hand.

EO04 Describe the processes of knurling, grooving, and form turning on a lathe

KNURLING, GROOVING, AND FORM CUTTING

Knurling – The forming of diamond-shaped or straight lined patterns into the surface of work for gripping purposes.

Process

Mount the work between centers and mark the area to be knurled. Lathe speed the lowest to start (one-quarter the speed required for turning) and increase as needed. Set carriage feed .015 - .030". Install and center knurling toolbit. Start lathe and check tracking. Move to start of knurling - end of work piece so that only half of the roller face is on work. Force knurling tool approx. 0.025" into work and start lathe. Check pattern without backing tool away. The most common problem is that tool is not centered. Restart lathe with automatic carriage feed engaged and apply cutting or lubricating oil to the knurling rolls. Knurl to proper length and depth. If pattern is not pointed - reverse lathe feed and take another cut.

Grooving

Also called recessing, undercutting and necking is often done at the end of a thread to permit full travel of the nut up to a shoulder, or at the edge of a shoulder to ensure a proper fit of mating parts.

Three common shapes of grooves are:

Round

Square

V-shaped


To machine a groove, grind toolbit to desired size and shape. Then layout the location of groove and set lathe speed to one-half normal cutting speed. Mount the workpiece and set the toolbit to center height. Position the toolbit on work where groove is to be cut. Start lathe and just touch work - zero collar. Calculate depth of cut and feed toolbit slowly with crossfeed handwheel. Apply cutting fluid to the point of the cutting tool. If chatter should develop – reduce spindle speed. Stop lathe and check groove depth.

Form Turning is used to form irregular shapes or contours on a workpiece and can be accomplished by one of these following methods: Freehand, Form-turning tools, special attachments and hydraulic tracer attachment.

Freehand turning is most difficult lathe operation to learn as coordination of both hands is required.

Form turning tools are used for smaller radii and contours. The shape and radius is ground on a toolbit and used to form contours on the workpiece. To produce a good finish by this method, work is turned slowly with cutting fluid added.

Templates and followers used when only a few pieces of special form are required.

Hydraulic tracer attachment may be used when many duplicate parts having several radii or contours that may be difficult to produce are required. The cross-slide is controlled by hydraulic pressure. A stylus follows template and controls oil pressure and the template is duplicated.

EO05 Describe the process of turning tapers on a lathe

TURNING TAPERS ON A LATHE

A taper is defined as a uniform change of diameter measured along its axis. Tapers are expressed in terms of taper per foot, taper per inch, or degree of taper.

Self-holding tapers, when seated properly, remain in position because of the wedging action of the small taper angle. The most common forms are the Morse, the Brown and Sharpe, and 3/4" per foot machine taper.

Steep Tapers (self-releasing) have a 3 1/2" taper per foot (tpf) and was formerly called the standard milling machine taper.

TPF Calculation is as follows:

Where D = large diameter and d= small diameter,

tpf = (D-d) x 12 length of taper


Three Methods of Turning a Taper are:

Tailstock offset

Taper attachment

Compound rest

Turning a taper using the Tailstock offset method is normally used when no taper attachment is available.

Calculation for using this method is as follows:

offset = D - d x L 2 x l

Loosen tailstock clamp and offset the tailstock the required amount. Set up cutting tool as for parallel cutting. Starting at small diameter - take successive cuts until taper is .050" - .060" oversized. Check taper for accuracy using a taper ring gage if necessary. Finish turn to correct size.

Taper Attachments provide several advantages. Lathe centers remain in alignment and setup is simple - no time is lost aligning centers. Length of workpiece is not as important and tapers can be produced between centers, in a chuck, or in a collet. Internal tapers can be turned by this method. Also, a wider range of tapers may be produced.

There are two types of taper attachments. With the plain taper attachment, the depth of cut is made with compound rest feed handwheel. With the telescopic taper attachment, the depth of cut is set by crossfeed handle.

Taper turning using compound rest or slide can be accomplished but you may have to calculate taper in degrees if it is not given. Set compound rest for taper and set cutting tool at right angle to the taper to be cut. Tighten toolholder securely. Move carriage to start of taper and then lock the carriage. Rough turn the taper by feeding compound rest handwheel. Check taper for accuracy and readjust the compound rest setting if necessary. Finish turn to size.

Checking tapers can be done by scribing lines exactly 1 inch apart and then carefully measuring the taper at these points with a micrometer. A taper ring gage is used to check external tapers while a taper plug gage is used for internal tapers. Taper micrometers measure tapers quickly and accurately while the workpiece is still in the machine.


EO06 Describe the processes of thread cutting on a lathe

THREAD CUTTING ON A LATHE

Threads may be defined as a helical ridge of uniform section formed on the inside or outside of a cylinder or cone. Threads are used for several purposes:

Fastening such as screws, bolts, studs and nuts

Accurate measurement as in a micrometer

Transmit motion like the lead screw on the lathe

Increase force as in a screw jack


Lathe Parts integral to cutting threads are:

Thread chasing dial which indicates when half-nut lever should be engaged

Half-nut lever which is also called the split-nut lever is engaged so that the toolbit follows the same course so as not to damage the threads.

To Set-up machine for threading, set speed to about ¼ the speed used for turning. Set quick change gear box for required pitch in threads per inch (tpi). Engage the lead screw. Secure a 60 degree threading toolbit in the toolholder and check the angle with a thread center gage. Set compound rest at 29 – 29 ½ degrees to the right for right hand thread, or to the left for left hand thread. Center the cutting tool to proper height. Mount the work as desired for your particular application. Set the toolbit at right angles to the work. Arrange apron controls to allow half-nut lever to be engaged.

Thread cutting is one of the more interesting operations to be performed on the lathe and it requires that the machinist pay close attention to the equipment and controls. Prior to cutting threads, check major diameter of the work for size. Start the lathe and chamfer the end to just below the minor diameter of the thread. Mark the length to be threaded by cutting a light groove at this point with the threading tool while the lathe is revolving. Move carriage to right hand end of work. Turn crossfeed handle until tool is close to work - leave handle in 3 o'clock position and set collar to zero. Turn compound rest until tool lightly touches work. Move carriage to the right past work and feed the compound rest for .003" cut. Engage half-nut at proper mark on dial and take trial cut. At end of cut, back off crossfeed handle and disengage half-nut lever. Stop the lathe and check thread for accuracy using a thread pitch gage.

After each cut, turn the carriage handwheel to bring toolbit to start of thread and return crossfeed handwheel to zero. Apply cutting fluid and take successive cuts until crest and root are the same width. Remove any burrs with light filing. Check thread with master nut and take further cuts if needed.

Checking Threads can be done in one of six ways, depending on the accuracy required.

Master nut

Thread micrometer

Three wires

Thread roll - snap gage

Thread ring - plug gage Thread pitch gages

Optical comparator


LESSON 3 TERMINAL OBJECTIVE

Given a Lathe machine operation using a "chuck", the Maintenance Mechanic will describe the various methods used and tooling required to

safely and properly operate the lathe using a chuck.


EO01 Describe the methods of mounting and machining work in a three-jaw chuck.

EO02 Describe the methods of mounting and machining work in a four-jaw chuck

EO03 Describe the process of facing, grooving, and cutting off work held in a chuck.

EO04 Describe the process of drilling holes using a lathe.

EO05 Describe the process of reaming and boring using a lathe.

EO06 Describe the process of tapping an internal thread using a lathe.


EO01 Describe the methods of mounting and machining work in a three-jaw chuck

MOUNTING AND REMOVING LATHE CHUCKS

Lathe chucks have adjustable jaws and work is generally shorter than work held between centers. If work is longer than three times its diameter, the end should be supported.

Mounting and Removing Chucks

Depending on the machine, set lathe to slowest speed and shut off power. Remove drive plate and live center and clean surfaces of the spindle nose and the mating parts of the chuck. Place chuck cradle (or block of wood) in front of spindle and place chuck in cradle. Slide cradle close to spindle nose and mount chuck.

There are three types of chuck attachment.

Threaded chucks should thread on freely by hand. Do not jam (slam) the chuck on as this may damage the threads.

Tapered chucks use a lock ring that is secured with a spanner wrench.

Cam-Lock lathe chucks have holes in the spindle that receive the cam-lock studs on the chuck. Registration lines on the spindle nose will indicate when the spindle is ready to receive the chuck and also when the chuck has been secured.

When removing a chuck, set lathe at slowest speed and stop the motor. Place cradle under chuck and remove chuck onto cradle. Use caution as lathe chucks are heavy and pinch points exist in this evolution.

THREE-JAW UNIVERSAL CHUCK

Assembling Jaws in a Three-Jaw Chuck. Two sets of jaws are usually supplied; one set for outside gripping and one set for inside gripping. These jaws are not interchangeable between chucks.

Clean jaws and jaw slides in the chuck. Turn the chuck key clockwise until the start of the scroll thread just shows on the back edge of Slide 1.Insert Jaw 1 into Slide 1 and press down while turning chuck wrench clockwise. After scroll thread engages, continue to turn until scroll thread is back of Slide 2 and insert Jaw 2 and continue until you are able to insert Jaw 3 in the same manner. Some three-jaw chucks use jaws that are fastened to master jaws with cap screws. These jaws can be reversed for inside gripping.

When mounting work, clean the chuck jaws and use the proper size chuck wrench and open jaws to proper size. Place work in chuck with no more than three times diameter extending out. Tighten jaws (all jaws move simultaneously)-Do not over tighten.

EO02 Describe the methods of mounting and machining work in a four-jaw chuck


THE FOUR-JAW INDEPENDENT CHUCK

All four jaws move independently and works well to hold odd-shaped work. Before mounting work, measure diameter of work and adjust jaws to approximate size using index line on face of chuck. Set work in chuck and snug up jaws.

True up work by one of following methods:

Chalk method - Start lathe and lightly touch chalk to diameter of work. Stop lathe and check chalk for high spots

Surface Gage Method- Place surface gage on lathe bed and adjust point of scriber to just touch work. Revolve lathe by hand to find low spot then loosen jaw nearest low spot and tighten opposite jaw. Repeat until work is true.

Dial Indicator Method (preferred) - Mount work and true approximately. Mount an indicator on a stationary part of lathe and bring indicator point against work until it registers. Turn lathe by hand and note highest and lowest readings. Loosen at lowest and tighten at highest until work is moved halfway between them. Continue to adjust these two readings until the indicator registers the same. Repeat with opposite set of jaws until indicator reads the same on any point. Rotate lathe by hand and check readings.

EO03 Describe the process of facing, grooving, and cutting off work held in a chuck

FACING, GROOVING, AND CUTTING OFF IN A CHUCK

Facing is done to obtain true, flat surface or cut the work to length. True up the work in the chuck. Have at least an amount equal to the diameter projecting from chuck jaws. Set compound rest at 90 degrees, if many shoulders are to be cut or 30 degrees to the right, for single surface is to be faced. Set facing toolbit to center height and pointing approx. 10 degrees to left. Lock the carriage and set the depth of cut on the compound rest, twice the amount to be removed if the compound rest is at 30 degrees and the exact amount to be removed if the compound rest is at 90 degrees. Use the normal cutting speed and feed tool by hand until it touches. Automatic feed to center of face. Make one or more rough cuts then finish cut from middle out. Projections left in middle if cutting tool is not set at center.

Cutting Off Work

Mount work with cutoff point as close to jaws as possible. Mount cut-off tool on left side of compound rest – center cutting tool. Place cutter as close to the toolpost as possible to avoid chatter and extend cutting blade half the diameter plus 1/8”. Set speed at one-half cutting speed. Start lathe and feed tool by hand. Keep steady feed and apply cutting fluid. Do not use cutting fluid on cast iron.

When grooving or cutting off deeper the ¼” – sideways movement of cutting tool prevents jamming. Just before cut is complete – remove burrs by light filing.

EO04 Describe the process of drilling holes using a lathe

DRILLING ON A LATHE

Center drilling creates a V-shaped shallow hole that acts as a guide for regular drill.


For regular drilling, mount work true in lathe chuck and set lathe to proper speed for material to be drilled. Check the tailstock to make sure it is in line. Spot the hole with a center drill then mount twist drill in tailstock spindle, drill chuck or drill holder. Start lathe and drill to desired depth - apply cutting fluid frequently. Use graduations on tailstock or measuring instrument to check hole depth. Back drill out often to remove chips.

EO05 Describe the process of reaming and boring using a lathe

REAMING AND BORING ON A LATHE

Steps in making a true hole:

Drill

Bore

Ream

Boring - The purpose of boring is to ensure that the hole is on location and is done by enlarging and truing a hole with a single point cutting tool. Special diameter holes can be produced. To accomplish this mount work, face, center drill, and drill hole 1/16" undersized. Select and mount boring bar and center toolbit. Set speed (normal cutting) and medium feed. Start lathe and touch work with toolbit. Take light trial cut and stop lathe and measure for accuracy. Determine amount to be removed and leave .010" -.020" for finishing cut. Set depth of cut, start lathe and take rough cut. Make finishing cut with fine feed.

Reaming is used to obtain an accurate sized hole. Drill and bore prior to reaming. With work mounted in chuck, center drill, drill and bore to .010" undersize. Mount machine reamer in drill chuck or drill holder. Speed is one-half normal cutting speed. Bring reamer close and lock tailstock. Start lathe, apply cutting fluid, and slowly feed reamer into bore with tailstock handwheel. Occasionally pull reamer out to clear chips and allow cutting fluid access. Never turn a reamer backwards for any reason as this will damage the reamer.

When hole is reamed, remove reamer from bore and stop the lathe. Clean and store reamer properly.


EO06 Describe the process of tapping an internal thread using a lathe

TAPPING A HOLE ON THE LATHE

Tapping is used to produce internal threads. The point of tailstock dead center is placed on shank end of tap to guide it and provide support. Tap handle is always turned by hand.

Process:

Mount work in chuck, face, and center drill. Select proper sized tap drill and set lathe to proper speed. Drill hole to required depth then chamfer edge of hole slightly. Stop lathe and lock spindle. Place tapered tap in hole and support tap shank with point of tailstock center. With the tap wrench handle, turn the tap, keeping the dead center snug against the shank by turning the tailstock handwheel. Back the tap out occasionally to break chip. Remove taper tap and finish tapping the hole with bottoming or plug tap. Check thread.

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