CHAPTER 1 : LATHE MACHINE By Virag A. Timbadia Lecturer – SBM Polytechnic CHAPTER 1 : LATHE MACHINE

Introduction Definition: Virag A. Timbadia Definition: Lathe is a machine, which removes the metal from a work piece to the required shape & size Principle: A lathe operates on the principle of a rotating work piece and a fixed cutting tool. The cutting tool is feed into the work piece, which rotates about its own Z-axis, causing the work piece to be formed to the desired shape.

Lathe Machine Components Virag A. Timbadia

Lathe Machine Components Virag A. Timbadia

Lathe Machine Components Virag A. Timbadia

Lathe Machine Components Virag A. Timbadia

Classification Lathe Machine Speed lathes Engine lathes Bench lathes Capstan and turret lathes Automatic lathes Computer controlled lathes Tracer lathes Tool Room lathes Special Purpose lathes Wood working Polishing Spinning Belt drive Gear head lathe Virag A. Timbadia Missile Lathe Gap Bed Lathe T-Lathe Wheel Lathe Duplicating Lathe

Speed lathes: High speed lathe with very few ranges of speed and use for wood working, centering polishing and spinning. Engine lathes: This is similar to the speed lathes but the head stock is little robust in construction. Engine lathes have additional mechanisms to produce a wide range of speeds. Bench lathes: This is a very small lathe and is generally mounted over a bench. These lathes are small in size and are generally used for doing small and precision works. Capstan and turret lathes: These are the developments made in engine lathe. These lathes found application in production work. In this lathes the tail stock is replaced by hexagonal turret. Based on the way the turret is mounted they will be classified in to capstan and turret lathes. Automatic lathes: Every operation is automatically done by employing computers. These lathes have high speed, heavy duty and are used for mass production. These lathes produce jobs with minimum tolerances and of very high accuracy.   Tracer lathes: a lathe that has the ability to follow a template to copy a shape or contour. Tool Room lathes: it is more accurately built and a wide range of speeds ranging from very low to very high speeds up to 2500rpm can be generated. This is used for doing precision works like tools dies etc. tool room lathes are costlier when compared to engine lathes of same size. Virag A. Timbadia

Specification 1. The length of bed : Virag A. Timbadia 1. The length of bed : It indicates the approximate floor space occupied by the lathe. 2. The length between centers : It is the maximum length of work that can be mounted between the lathe centers.

Specification BED SWING DIAMETER OVER BED HEIGHT OF CENTRE FROM BED SWING DIAMETER OVER CARRIAGE CARRIAGE 3. The height of centers from the bed : It is the distance between top surface of the bed and the imaginary center line passing through live centre and dead centre. 4. The maximum bar diameter : It is the maximum diameter of work that will pass through the hole of the head stock spindle. 5. The swing diameter of work over bed : It is the largest diameter of work that will revolve without touching the bed. It is twice the height of the centres from the bed. 6. The swing diameter of work over the carriage : It is the largest diameter of work that will revolve over the lathe saddle. It is smaller than the swing diameter over bed. Virag A. Timbadia

Lathe Tools Virag A. Timbadia

Components Lathe Bed & Ways Head Stock Speed Gears Feed Gears Virag A. Timbadia Lathe Bed & Ways Head Stock Speed Gears Feed Gears Thread Chasing Dial (1/2 Nut) Carriage Cross Slide Compound Tail Stock Coolant System

Components BED The bed of the lathe provides the foundation for the entire machine and holds various components like headstock, tailstock and carriage in alignment. Virag A. Timbadia WAY The surfaces of the bed that are finely machined - and upon which the carriage and tailstock slide - are known as "ways".

Components HEADSTOCK The headstock of the lathe contains all of the gearing necessary to change Spindle speed Carriage feed and Threading selections. SPEED & FEED GEARS The lathe “speed” and “feed” charts are affixed to the front of the headstock to allow the operator to make the proper feed and speed selections based on the Virag A. Timbadia

Components Virag A. Timbadia CARRIAGE ASSEMBLY

Components Virag A. Timbadia CARRIAGE OPERATING CONTROL

Components Lead & Feed Screw Single Tool Tool-Post Magnetic Tool Post Virag A. Timbadia Single Tool Tool-Post Apron Msm.

Components Tool Post Compound Virag A. Timbadia Cross Slide Handles

Components Tail Stock Tail Stock Mechanism Cam Lock Handwheel Barrel Virag A. Timbadia Cam Lock Handwheel Barrel

Lathe Accessories Divided into two categories Work-holding, - Supporting, & - Driving Devices Lathe centers, chucks, faceplates Mandrels, steady and follower rests Lathe dogs, drive plates Cutting-tool-holding devices Straight and offset tool holders Threading tool holders, boring bars Turret-type tool posts Virag A. Timbadia

Lathe Centers Work to be turned between centers must have center hole drilled in each end Provides bearing surface Support during cutting Most common have solid Morse taper shank 60º centers, steel with carbide tips Care to adjust and lubricate occasionally Virag A. Timbadia

Removing & Mounting Lathe Centers Live center Use knockout bar pushed through headstock spindle (slight tap) Use cloth over center and hold to prevent damage Dead center Turn tailstock hand wheel to draw spindle back into tailstock End of screw contacts end of dead center, forcing it out of spindle Remove any burrs from lathe spindle, centers, or spindle sleeves Clean tapers on lathe centers and in headstock and tailstock spindles Partially insert cleaned center in lathe spindle Force center into spindle Follow same procedure when mounting tailstock center Check trueness of center Use dial indicator Virag A. Timbadia

Revolving Tailstock Centers Replaced solid dead centers for most machining operations Used to support work held in chuck or when work is being machined between centers Contains antifriction bearings which allow center to revolve with work piece No lubrication required between center and work Types: revolving dead center, long point center, and changeable point center Virag A. Timbadia

Microset Adjustable Center Fits into tailstock spindle Provides means of aligning lathe centers or producing slight tapers on work machined between centers Eccentric slide (dovetail) allows center to be adjusted limited amount to each side of center Self-Driving Live Center Virag A. Timbadia Mounted in headstock spindle Used when entire length of work piece is being machined in one operation Chuck or lathe dog could not be used to drive work Grooves ground around circumference of lathe center point provide drive Work usually soft material such as aluminum

Chucks Used extensively for holding work for lathe machining operations Work large or unusual shape Most commonly used lathe chucks Three-jaw universal Four-jaw independent Collets chuck Virag A. Timbadia

Three-jaw Universal Chuck Virag A. Timbadia Holds round and hexagonal work Grasps work quickly and accurate within few thousandths/inch Three jaws move simultaneously when adjusted by chuck wrench Caused by scroll plate into which all three jaws fit Two sets of jaw: outside chucking and inside chucking

Four-Jaw Independent Chuck Virag A. Timbadia Used to hold round, square, hexagonal, and irregularly shaped work pieces Has four jaws Each can be adjusted independently by chuck wrench Jaws can be reversed to hold work by inside diameter

Collet Chucks Most accurate chuck Used for high-precision work Virag A. Timbadia Most accurate chuck Used for high-precision work Spring collets available to hold round, square, or hexagon-shaped work pieces Each collet has range of only few thousandths of an inch over or under size stamped on collet

Spring Collet Chucks Spring - collet chuck One form: Hand wheel draws collet into tapered adapter Another form: Uses chuck wrench to tighten collet on work piece Can hold larger work than draw-in type | Virag A. Timbadia

Jacobs Collet Chuck Jacobs collet chuck Virag A. Timbadia Jacobs collet chuck Utilizes impact-tightening hand wheel to close collets Wider range than spring-collet chuck

Magnetic Chucks Virag A. Timbadia Used to hold iron or steel parts that are too thin or may be damaged if held in conventional chuck Fitted to an adapter mounted on headstock spindle Used only for light cuts and for special grinding applications

Headstock Spindle Types 1. Threaded spindle nose: Screws on in C.W. direction 2. Cam-lock spindle nose: Held by tightening cam-locks using T-wrench Chuck aligned by taper on spindle nose 3. Tapered spindle Nose: Held by lock nut that tightens on chuck Virag A. Timbadia

Faceplates Used to hold work too large or shaped so it cannot be held in chuck or between centers Usually equipped with several slots to permit use of bolts to secure work Angle plate used so axis of work piece may be aligned with lathe centers Counterbalance fastened to faceplate when work mounted off center Prevent imbalance and resultant vibrations Virag A. Timbadia

Steady rest Used to support long work held in chuck or between lathe centers Prevent springing Located on and aligned by ways of the lathe Positioned at any point along lathe bed Three jaws tipped with plastic, bronze or rollers may be adjusted to support any work diameter with steady rest capacity Virag A. Timbadia

Follower Rest Mounted on saddle Travels with carriage to prevent work from springing up and away from cutting tool Cutting tool generally positioned just ahead of follower rest Provide smooth bearing surface for two jaws of follower rest Virag A. Timbadia

Mandrel Holds internally machined work piece between centers so further machining operations are concentric with bore Several types, but most common are: -Plain Mandrel -Expanding Mandrel -Stub Mandrel -Gang Mandrel Plain Mandrel Stub Mandrel Virag A. Timbadia Gang Mandrel Expanding Mandrel

Lathe Dogs Drives work machined between centers Has opening to receive work and setscrew to fasten the dog to work Tail of dog fits into slot on drive plate and provides drive to work piece Made in variety of sizes and types to suit various work pieces Standard bent-tail lathe dog: Most commonly used for round work pieces Available with square-head setscrews of headless setscrews Bent tail engages in slot on drive plate Virag A. Timbadia

Lathe Dogs Straight-tail lathe dog Driven by stud in drive plate Virag A. Timbadia Straight-tail lathe dog Driven by stud in drive plate Used in precision turning Safety Clamp lathe dog Used to hold variety of work Wide range of adjustment Heavy Duty lathe dog Wider Range than others Used on all shapes

Cutting Tool-Holding Devices Available in three styles Left-hand offset Right-hand offset Straight Each has square hole to accommodate square tool-bit held in place by setscrew Angle of approximately 15º to 30º to base of tool-holder Virag A. Timbadia

Offset Tool holder LH Offset tool holder Offset to the right Designed for machining work close to chuck or faceplate and cutting right to left Designated by letter L RH Offset tool holder Offset to the left Designed for machining work close to the tailstock and cutting left to right Designated by letter R Virag A. Timbadia

Tool holder Straight Tool Holder General-purpose type Used for taking cuts in either direction and for general machining operations Designated by letter S Carbide Tool Holder Has square hole parallel to base of tool holder to accommodate carbide- tipped tool bits Holds tool bit with little or no back rake Designated by letter C Virag A. Timbadia

Cutting-Off (Parting) Tools Virag A. Timbadia Used when work must be grooved or parted off Long, thin cutting-off blade locked securely in tool holder by either cam lock or locking nut Three types of parting tool holders Left-hand Right-hand Straight

Threading Toolholder Virag A. Timbadia Designed to hold special form-relieved thread-cutting tool Has accurately ground 60º angle Maintained throughout life of tool Only top of cutting surface sharpened when becomes dull

Boring Tool holders Held in standard tool post Light boring tool holder Used for small holes and light cuts Medium boring tool holder Suitable for heavier cuts May be held at 45º or 90º to axis of bar Mounted on compound rest of lathe Heavy-duty boring bar holder Three bars of different diameters Virag A. Timbadia

Compound Rest Tooling Systems Virag A. Timbadia Standard, or round, tool post Generally supplied with conventional engine lathe Fits into T-slot of compound rest Provides means of holding and adjusting type of tool holder or cutting tool required Concave ring and the wedge or rocker provide for adjustment of cutting-tool height

Conventional Tool Posts Virag A. Timbadia

Modular (Quick-Change) Tooling Initially developed for CNC machine tools to improve accuracy, reduce tool-change time and increase productivity Benefits realized on conventional lathes with systems designed for these machines Modular tooling system must be rigid, accurate and have quick-change capabilities Basic clamping unit or turret can hold variety of cutting tool modules Principal function is to reduce cost of keeping large tool inventory Tools can be specifically mounted to suit characteristics of work piece More common systems available The Super Quick-Change Tool post The Quadra* Index Tool post The Super-Six Index Turret The Vertical Index Turret Virag A. Timbadia

Super Quick-Change Tool post Virag A. Timbadia Provides fast, accurate, and reliable method of quickly changing and setting various tool holders for different operations Locking system has two sliding gibs forced out against tool holder Handle pulled into lock position Provides rigid, positive lock with zero backlash

Quadra* Index Tool post Virag A. Timbadia Allows four tools to be mounted on turret at same time Each tool locked independently Provides flexibility to use from one to four tools simultaneously Unique indexing system of turret allows it to be set in 24 positions (every 15º)

Super-Six Index Turret Virag A. Timbadia Designed to simplify and increase machining productivity on engine lathes when multi-operation jobs require use of more than one tool Up to six tools for external and internal machining operations Allows height adjustment for each tool Tool changes can be made in less than 1 sec

Vertical Index Turret (VIT) Designed to give highest accuracy, fastest tool change and greatest rigidity of any tool system available for engine lathes Same concept as indexing turrets on CNC lathes Can hold up to six or eight tools Closest to performance of CNC lathes Virag A. Timbadia

Alignment Test Lathe Centers When lathe center aligned Parallel diameters produced Three common methods used to align Aligning tailstock Trial Cut Test Bar and Indicator Leveling of the Machine True Running of Work Piece Virag A. Timbadia

Aligning Tail Stock Aligning centerlines on back of tailstock with each other Only a visual check and not too accurate Loosen tailstock clamp nut or level Loosen one of the adjusting screws, depending on direction tailstock must be moved and tighten other until line on top aligns with line on bottom half Tighten screw to lock both halves in place Make sure tailstock lines still aligned Lock tailstock clamp nut or lever Virag A. Timbadia

Trial-Cut Method Small cut taken from each end of work Diameters measured with a micrometer Take a light cut (.005-.010 in.) to true diameter from section at tailstock end about .250 in. long Stop feed and note reading on graduated collar of cross feed handle Move cutting tool away from work with cross feed handle Bring cutting tool close to headstock end Return cutting tool to same graduated collar setting as at first cut Cut a .500-in (13 mm) length at headstock end and stop lathe Measure both diameters with micrometer Virag A. Timbadia If both diameters not same size, adjust tailstock either toward or away from cutting tool ½ difference of two readings Take another light cut at both points at same cross feed graduated collar setting Measure diameters and repeat.

Test bar and dial indicator Clean lathe and work center, mount test bar Adjust test bar snugly between centers and tighten tailstock spindle clamp Mount dial indicator on tool post or lathe carriage : Indicator plunger should be parallel to lathe bed and contact point set on center Adjust cross-slide : Indicator registers approximately .025 in at tailstock, indicator bezel to 0 Move carriage by hand so indicator registers on diameter at headstock end and note indicator reading If both indicator readings not same, adjust tailstock with adjusting screws until indicator registers same at both ends Tighten adjusting screw & tail stock clamp nut that was loosened Adjust tailstock spindle until test bar snug between lathe centers Recheck indicator readings at both ends and, if necessary, adjust tailstock Virag A. Timbadia

Three Important Elements Rotating Speed It expresses with the number of rotations (rpm) of the chuck of a lathe. When the rotating speed is high, processing speed becomes quick, and a processing surface is finely finished. It is better to set low rotating speed at the first stage. Cutting Depth The cutting depth of the tool affects to the processing speed and the roughness of surface. When the cutting depth is big, the processing speed becomes quick, but the surface temperature becomes high, and it has rough surface. Feed (Sending Speed ) The sending speed of the tool also affects to the processing speed and the roughness of surface. When the sending speed is high, the processing speed becomes quick. When the sending speed is low, the surface is finished beautiful. Virag A. Timbadia

Mechanisms Half Nut Mechanism Cam Slot Guide or Frame Lead Screw Hand Lever Pin Circular Plate Half Nuts Virag A. Timbadia Half Nut Mechanism

Lathe Operations Virag A. Timbadia

Turning Virag A. Timbadia

Straight Turning Virag A. Timbadia

Taper Turning Set Over = L x (D−d) 2L = (D−d) L Methods of Taper Turning By a broad nose form tool By setting over the tailstock center By swiveling the compound rest By taper turning attachment By Combining longitudinal and cross feed in a special lathe 1. 2. Set Over = L x (D−d) 2L = (D−d) L 3. Virag A. Timbadia

Taper Turning 4. 5. Virag A. Timbadia

Facing Virag A. Timbadia

Drilling Virag A. Timbadia

Boring Virag A. Timbadia

Tapping Virag A. Timbadia

Threading Virag A. Timbadia

Knurling Virag A. Timbadia

Reaming Virag A. Timbadia

Radius Forming Virag A. Timbadia

Grooving Virag A. Timbadia

Parting Virag A. Timbadia

Eccentric Virag A. Timbadia

Filing & Polishing Virag A. Timbadia

Filing & Polishing Virag A. Timbadia

Thank - You Virag A. Timbadia