mem07006c perform lathe operations - vetres · if the tool thread form is not square to the axis...

MEM05 Metal and Engineering

Training Package

Learner guide

Version 1

Training and Education Support

Industry Skills Unit

Meadowbank

Product code: 5514

MEM07006C

Perform lathe operations

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© TAFE NSW (Training & Education Support Industry Skills Unit Meadowbank)

2012

MEM07006C Perform lathe operations

AcknowledgmentsThe TAFE NSW Training and Education Support Industry Skills Unit, Meadowbank would like to acknowledge the support and assistance of the following organisations and people in the production of this learner guide:

BHP Machinist bookElectricity Commission of NSW (Lathe manual)Fitting and Machining book two NSW TAFEFitting and Machining Ron CulleyHare & Forbes machinery houseIscar AustraliaMitushitshi materialsSeco

Writer:Andrew Gill

Reviewer:Bruce Blackshaw (Sydney Institute)

Project Manager:Stephen DaviesEducation Programs ManagerTAFE NSW

EnquiriesEnquiries about this and other publications can be made to:

Training and Education Support Industry Skills Unit, Meadowbank Meadowbank TAFE Level 3, Building J, See Street, MEADOWBANK NSW 2114

Tel: 02-9942 3200 Fax: 02-9942 3257

© TAFE NSW (Training and Education Support, Industry Skills Unit Meadowbank) 2012

Copyright of this material is reserved to TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank. Reproduction or transmittal in whole or in part, other than for the purposes of private study or research, and subject to the provisions of the Copyright Act, is prohibited without the written authority of TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank.

ISBN 978-1-74236-259-5

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Table of ContentsIntroduction ................................................................................... 9

1. General introduction ............................................................................. 9

2. Using this learner guide ......................................................................... 9

3. Prior knowledge and experience ........................................................... 11

4. Unit of competency overview ............................................................... 11

5. Assessment ....................................................................................... 15

Topic 1: Lathe setup ..................................................................... 17

Safety .................................................................................................. 17

Using the digital readout ........................................................................ 19

Lathe lubrication and maintenance ........................................................... 21

Review questions ................................................................................... 27

Topic 2: Work holding methods .................................................... 31

Lathe chucks ......................................................................................... 31

Face plate turning .................................................................................. 38

Steadies ............................................................................................... 40

Mandrels ............................................................................................... 45


Topic 3: Machining operations ...................................................... 53

Parallel/straight turning ........................................................................... 54

Facing .................................................................................................. 56

Shoulders, corners, undercuts, grooves ..................................................... 58

Boring .................................................................................................. 62

Counterboring........................................................................................ 66

Drilling ................................................................................................. 66

Reaming ............................................................................................... 68

Tapping in the lathe ................................................................................ 71

Knurling in the lathe ............................................................................... 72


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Topic 4: Tapers ............................................................................. 83

Methods of expressing tapers ................................................................... 85


Topic: 5 Screwcutting ................................................................. 101

Thread terms ........................................................................................101

Thread calculations ................................................................................103

Thread calculations ................................................................................104

Thread fits ...........................................................................................105

Thread cutting tools ...............................................................................106

If the tool thread form is not square to the axis thread produced it is said to be

"drunken" or wobbles along the axis of the shaft. ......................................108

Thread cutting in the lathe .....................................................................108

Tracking the thread ...............................................................................112

Method of cutting threads .......................................................................116

Methods used to measure and check the thread ........................................122

Review questions .................................................................................126

Topic 6: Principles of metal chip formation ................................. 135

Factors affecting metal cutting ................................................................135

Effects of cutting conditions for turning ....................................................136

Optimal tool cutting conditions ................................................................140

Cutting tool materials and properties .......................................................146

Grades of carbide inserts ........................................................................149

Chip control mechanisms .......................................................................157

Review questions ..................................................................................166

Suggested practical jobs ............................................................ 173

Job 1: Bearing greaser ...........................................................................174

Job 2: Taper turning .............................................................................178

Job 3: Screwcutting blank ......................................................................183

Job 4: Screwcutting ...............................................................................186

Job 5: Internal screwcutting ...................................................................189

Job 6: Drive shaft .................................................................................192

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Job 7: Screwcut driveshaft and machine circlip groove ..............................195

Job 8: Marking out bearing housing .........................................................198

Job 9: Faceplate turning and boring ........................................................201

Job 10: Manufacture bearing ..................................................................204

Job 11: Flat belt pulley...........................................................................207

Resource Evaluation Form .......................................................... 211

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© TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 17 of 214

Topic 1: Lathe setup

SafetyThe Work, Health and Safety Act 2011 (WHS Act) and WHS Regulations are enforced throughout all Australian States and Territories. This legislation is aimed at providing consistency, certainty and clarity across Australia making it easy to understand workplace health and safety responsibilities. Consequently this act and its regulations requires both employers and employees to take every reasonable step to work safely and responsibly in the workplace.

There are no “short cuts” to working safety, its everyone’s responsibility to manage and minimise potential risks in the workplace, report faulty equipment as well as unsafe environments. Detailed information relating to the WHS Act and regulations can be found on:

• WorkCover Authority of NSW website; www.workcover.nsw.gov.au or on

• Safe Work Australia; www.safeworkaustralia.gov.au

Welding operators must know about the principles governing the welding operation, equipment used and workplace health and safety precautions required. The following points need to be taken into account when working in a welding environment.

Lathe operators must be constantly aware of the safety hazards that are associated with using the lathe and must know all safety precautions to avoid accidents and injuries. Carelessness and ignorance are two great menaces to personal safety. Other hazards can be mechanically related to working with the lathe, such as proper machine maintenance and setup. Some important safety precautions to follow when using lathes are:

• Sign off Safe Operating Procedure (SOP)

• Keep work area clean. Have clean areas for tools and measuring instruments

• Undertake familarisation session PRIOR to any operation of lathe. Have sign off sheet signed by your supervisor prior to commencement

• Make sure all safety guards and switches are installed and working

• Make sure job and accessories are secured before taking a cut

• Know where MSDS are kept. Refer to them

• Know the location of first aid station/location and First Aid Officer

• Report all injuries to your teacher or supervisor

• Do not remove danger tags

• Complete a risk assessment prior to commencement of any operations on the lathe

• Use all necessary Personal Protective Equipment (PPE) – glasses, hair restraint, safety footware, long sleeve shirts and long pants

• Isolate electrical switch prior to removing chuck

• Use the brake correctly

• Always remove chuck key before starting chuck.

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© TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012Page 18 of 214

• Always tighten ALL cam locks or hold on screws before starting chuck

• Do not allow coolant to flow onto the chuck

• Beware of sharp tools in tool post and tailstock

• Do not place items on the lathe headstock

• Use the correct equipment to remove swarf

• Use a chuck board and correct lifting technique when removing chucks.

Lathe safety features

Chuck safety guard

The chuck safety guard protects the operator from projectiles emanating from the rotating chuck; a safety interlock switch stops the chuck from rotating unless the guard is lowered.

Lead screw coversUsed to reduce the chance of entanglement and also reduce leadscrew wear as machining contaminants are kept of the screw thread.

Guard Cover

Travelling chip guardSome lathes have an optional travelling chip guard this guard can be positioned over the tool post and cutting area protecting the operator from flying swarf and coolant spray.

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Feed clutchThe adjustable feed torque clutch enables the operator vary the torque transmitted through the carriage feed mechanism thus reducing the effect of running the tool into the chuck or a shoulder on the job accidentally.

Torque clutch

Emergency stop and BrakeThe emergency foot brake stops the rotating spindle rapidly using an electromagnetic or mechanical brake and also disconnects the electric motor.

Foot brake

Using the digital readout A digital readout (DRO) replaces existing calibrated feed-screw dials with an independent measuring and display device.

Digital read-out units are, due to advancements in technology, becoming more common on lathes and a wide variety of machinery in modern machine shops.

DROs may be fitted on new machine tools as standard accessories or may also be retro-fitted to older existing machinery. The fitting of these units contribute to the elimination of machining errors that may occur due to:

• backlash

• parallax error

• misreading of graduation

• misreading of knob rotation

• miscalculation of dimensions

• screwthread wear.

A major factor contributing to the elimination of errors is that DROs only register the movement of slides, eliminating errors that may occur due to worn machine slides. The use of DROs gives the operator a vast variety of machining and measuring options such as:

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• Working in either metric or imperial and converting from either at any time without the loss of accuracy or datum’s

• The display may be zero-set at any slider position along the beam for incremental comparison measurement

• Cross-slide measurement may be displayed in either diameter or radius and can be switched from either at any time without the loss of position accuracy

• Centre axes datum may be set to zero or a required offset, eliminating the requirement for constant checking of diameters.

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Two axis lathe digital readout

1. Using the 'zero' keys to set datum points

A standard DRO will show an XY position on two displays. Each axis display can be individually zeroed to set a datum point. For example, when threading in the lathe the datum can be set at the outside diameter of the unthreaded bar. The crossslide can now be advanced for each cut until the correct depth of thread is reached. With the datum set at the outside diameter then rapid repositioning is possible because by looking for the reading changing from negative to positive you know the tool is in the metal. The next increment can be added and the cut taken.

2. Using the 'units' key: switching between metric (mm) and Imperial (inches)

The second common facility on a DRO is the ability to display the position in either inches or millimetres. This has uses beyond the obvious one where a drawing is in millimetres, but the machine in inches.

3. Direct Entry key pad:

Allows operator to manually input desired dimension / coordinate.

4. Centre Find Function:

Automatically calculates the centre of the workpiece after the edges are located.

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5. ABS/INC (Absolute/Incremental)

Allows the operator to switch between absolute and incremental display. 'Absolute' display references the work piece zero coordinate you designate. You may choose the absolute centre point of your workpiece or perhaps a corner of your workpiece, the decision is yours. Incremental display references any arbitrary coordinate/position without losing your designated zero point.

For example, to locate a point exactly in the middle of your workpiece you would most likely use 'absolute' display to locate the point. To locate points exactly .78 distant from an arbitrary point somewhere in the middle of your workpiece, you would then switch to 'incremental' display, designate the present position as a zero point, and then simply move your workpiece until .78 was displayed.

6. Using the 'scale' key: radius/diameter key

The Measuring Readout can be used on many different type of machine tool, and the ability to find the halfway point between two positions will be useful. But on a lathe this is not the case; finding half of a diameter or length is not overly useful. Therefore the Measuring Readout allows the 'scale' key to be changed to something more useful for a lathe, that is displaying in either radius (rad) or diameter (dia) dimensions for the X axis. If 'rad' is selected then the display will show the correct distance moved: moving the X axis 2.0 mm will result in the position changing by 2.0 mm.

But if the 'dia' reading is selected then all movements on the X axis are doubled, so moving the X axis 2.0 mm will result in the position display changing by 4.0 mm. This is therefore displaying the change in diameter of the work, not the depth of cut. On a lathe the choice between displaying the depth of cut as the 'rad' or the change in diameter as the 'dia' can be changed by pressing the 'scale' key. Which of these is selected is shown by the illuminated indicators; if both are illuminated then the milling machine 'half' function is selected.

7. Pre-setting a position

Being able to turn and directly display the diameter is of considerable help; but how do you know what the diameter should be? The tool can be advanced to the exact centre-line of the work, and the X axis zeroed to give a datum. This will now give the correct diameter readings with that particular tool. The snag of course lies in the word 'exact'; if the centre datum is out by 0.1 mm, then the diameters will be out by 0.2 mm.

To remove this problem the Measuring Readout allows a position to be pre-set for either axis. The work is set up in the lathe so that a light skim cut can be made; this cut needs to have as good a surface finish as possible. The diameter of this cut, the reference cut, is then measured. With the Measuring Readout in 'dia' mode, the diameter of the reference cut is then entered into the X axis display. Until either the tool or work is changed the X axis will show the diameter being turned.

Lathe lubrication and maintenanceThe engine lathe is a precision machine tool and must be treated with great care. Regular cleaning and maintenance will help to assure that the lathe will maintain its service life and accuracy for many years. The procedures you find within this document should be able to be performed by apprentices or beginning machine tool students. Lathe maintenance that requires more extensive disassembly should only be done by, or under the supervision of, qualified personnel.

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Drive belts

The drive belts supply power from the motor to the spindle. Access to the drive belts is gained by removing the end guards on the headstock. Make sure that all power is locked out before removing any guards.

Drive belts come in matched sets and should only be replaced with a matched set of belts. Visually inspect the drive belts for excessive wear and cracking. If you notice that one or more of the drive belts appear to be excessively worn or cracked, replace the complete set of belts.

Check the belt tension by applying finger pressure to each belt at a point midway between the two pulleys. For correct tension a deflection of about 10 mm should be evident in each belt.

If the amount of deflection is more than 10 mm in any one or more of the belts, the belt tension will need to be adjusted. Adjustment is made by pivoting the motor base using the two adjusting bolts.

Gib adjustment

All lathes employ precision slideways. The saddle, crossslide, and the compound slide all ride along a box slide way or dovetail slide way. After time the parts that ride along the slide ways begin to wear.

To compensate, machine tools are equipped with adjustable parts called gibs that allow you to eliminate space created by wear between the slide ways.

There are two types of gibs, straight gibs and tapered gibs. Straight gibs are adjusted by screws spaced out along the length of the gib. The screws push the gib in to create more contact with the sliding mechanisms.

Tapered gibs use two screws. The screws are located in each end of the tapered gib. One screw acts as an adjustment while the other screw acts as a locking mechanism. Because tapered gibs are wider on one end than the other, they slide in or out creating more or less contact between the sliding mechanisms.

Checking belt tension

Motor base

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mem07006c perform lathe operations - vetres · if the tool thread form is not square to the axis...

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