LatheMachine

INTRODUCTION-Accurate and versatile machine-Operations>Turning, tapering, form turning, threading, facing, drilling, boring, knurling, screw thread and cutting taper turning.-The main function of a lathe is to remove metal from a job to give it the required shape and size.-The job is securely and rigidly held in the chuck or in between centers on the lathe machine and then turn it against a single point cutting tool which will remove metal from the job in the form of chips.

Lathe Size

kra07228_4501L

big lathes 1

Parts of the Lathe

kra07228_4502L

Lathe Bed

Lathe Bed 1-The bed is a heavy ,rugged casting made to support the working parts of the lathe

Headstock

-The headstock is clamped on the left hand side of the bed.-The headstock spindle, a hollow cylindrical bar supported by bearings, provides a drive through gears or pulleys from the motor to work holding devices.

Lathe Headstock

Quick-Change Gearbox-Contains number of different-size gears-Provides feed rod and lead-screw with various speeds for turning and thread-cutting operations>Feed rod advances carriage when automatic feed lever engaged>Lead screw advances the carriage for thread-cutting operations when split-nut lever engaged

Lathe Gear Mechanism

Top ViewCarriage

Lathe Carriage 2

Cross-slide-Mounted on top of saddle-Provides manual or automatic cross movement for cutting tool-Compound rest (fitted on top of cross-slide)>Used to support cutting tool>Swiveled to any angle for taper-turning>Has graduated collar that ensure accurate cutting-tool settings (.001 in.) (also cross-slide)

Cross Slide Mechanism

Apron-Fastened to saddle-Houses gears and mechanism required to move carriage or cross-slide automatically-Locking-off lever inside apron prevents engaging split-nut lever and automatic feed lever at same time-Apron hand wheel turned manually to move carriage along lathe bed

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Automatic Feed Lever-Engages clutch that provides automatic feed to carriage-Feed-change lever can be set for longitudinal feed or for crossfeed>In neutral position, permits split-nut lever to be engaged for thread cutting>Carriage moved automatically when split-nut lever engaged

Tailstock-Upper and lower tailstock castings-Adjusted for taper or parallel turning by two screws set in base-Tailstock clamp locks tailstock in any position along bed of lathe-Tailstock spindle has internal taper to receive dead center>Provides support for right-hand end of work

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Setting Speeds on a Lathe-Speeds measured in revolutions per minute>Changed by stepped pulleys or gear levers-Belt-driven lathe>Various speeds obtained by changing flat belt and back gear drive-Geared-head lathe>Speeds changed by moving speed levers into proper positions according to r/min chart fastened to headstock

Types of lathe chuck

LATHE MACHINE PROCESS

Facing process Parallel process

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Drilling process Knurling process

Knurling-Process if impressing a diamond-shaped or straight-line patter into the surface of the workpiece>Improve its appearance>Provide better gripping surface>Increase workpiece diameter when press fit required

G:\kra07228_ch53\kra07228_5301.jpg-Diamond- and straight-pattern rolls available in three styles>Fine>Medium>Course

Knurling Tool-Toolpost-type toolholder on which pair of hardened-steel rolls mounted

G:\kra07228_ch53\kra07228_5302L.jpg>Knurling tool with
one set of rolls in
self-centering head

G:\kra07228_ch53\kra07228_5302L.jpg>Knurling tool with
three sets of rolls
in revolving head

Grooving-Done at end of thread to permit full travel of nut up to a shoulder or at edge of shoulder for proper fit-Also called recessing, undercutting, or necking-Rounded grooves used where there is strain on part

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Thread Terminology-Screw thread>Helical ridge of uniform section formed on inside or outside of cylinder or cone-External thread>Cut on external surface or cone-Internal thread>Produced on inside of cylinder or cone

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G:\kra07228_ch55\kra07228_5502L.jpgRight-hand thread>Helical ridge of uniform cross section onto which nut is threaded in clockwise direction>When cut on lathe, toolbit advanced from right to left

G:\kra07228_ch55\kra07228_5502L.jpgLeft-hand thread>Helical ridge of uniform cross section onto which nut is threaded in counterclockwise direction>When cut on lathe, toolbitadvanced from left to right

TOOL BIT ANGLES

Safety Precautions-Always wear approved safety glasses-Rollup sleeves, remove tie and tuck in loose clothing-Never wear ring or watch-Do not operate lathe until understand controls-Never operate machine if safety guards removed-Stop lathe before measure work or clean, oil or adjust machine-Do not use rag to clean work or machine when in operation>Rag can get caught and drag in hand-Never attempt to stop a lathe chuck or driveplate by hand-Be sure chuck or faceplate mounted securely before starting>If loose, becomes dangerous missile-Always remove chuck wrench after use>Fly out and injure someone>Become jammed, damaging wrench or lathe-Always remove chips with brush>Chips can cause cuts if use hands>Chips become embedded if use cloths-Always remove sharp toolbit from toolholder when polishing, filing, cleaning, or making adjustments