GOVT . POLYTECHNIC MEHAM Prepared by :- Jagdeep Sangwan

LATHE MACHINE

INTRODUCTION Lathe is one of the oldest important machine tools in the metal working industry. A lathe operates on the principle of a rotating work piece and a fixed cutting tool. A rope wound round the work with its own end attached to a flexible branch of tree and other end being pulled by man caused job to rotate intermittently. With its further development a strip of wood called “lath” was used to support the rope and that is how the machine came to be known as “lathe”. The cutting tool is feed into the workpiece, which rotates about its own axis, causing the workpiece to be formed to the desired shape. Lathe machine is also known as “the mother/father of the entire tool family”.

HISTORY The Lathe Machine is one of the oldest and most important machine tools. As early as 1569, wood lathes were in use in France. The lathe machine was adapted to metal cutting in England during the Industrial Revolution. Lathe machine also called “Engine Lathe” because the first type of lathe was driven by a steam engine.

INVENTOR OF CENTRE LATHE Henry Maudsley was born on an isolated farm near Gigghleswick in North Yorkshire and educated at University Collage London. He was an outstandingly brilliant medical student, collecting ten Gold Medals and graduating with an M.D. degree in 1857.

7. COMPUTER CONTROLLED LATHE TYPES OF LATHE 1. ENGINE LATHE 2. BENCH LATHE 3. TRACER LATHE 4.TOOL ROOM LATHE 5. AUTOMATIC LATHE 6. TURRET LATHE 7. COMPUTER CONTROLLED LATHE

Engine Lathe :- This term ‘engine’ is associated with the lathe owing to the fact that early lathes were driven by steam engine. It is also called centre lathe. The most common form of lathe, motor driven and comes in large variety of sizes and shapes.

CONTINUE… Belt Driven Lathe Motor Driven Lathe Gear Head Lathe Engine lathes are classified according to the various designs of headstock and methods of transmitting power to the machine. Belt Driven Lathe Motor Driven Lathe Gear Head Lathe The power to the engine lathe spindle may be given with the help of a belt drive from an overhead line shaft but most modern machines have a captive motor with either a cone pulley driven or an geared headstock arrangement.

Bench Lathe :- A bench top model usually of low power used to make precision machine small work pieces. It is used for small w/p having a maximum swing of 250 mm at the face plate. Practically it consists of all the parts of engine lathe or speed lathe.

Tracer Lathe :- A lathe that has the ability to follow a template to copy a shape or contour.

Tool Room Lathe:- A tool room lathe having features similar to an engine lathe is much more accurately built and has a wide range of spindle speeds ranging from a very low to a quite high speed up to 2500 rpm. This lathe is mainly used for precision work on a tools, dies, gauges, and in machining work where accuracy is needed. This lathe machine is costlier than an engine lathe of the same size.

Automatic Lathe :- A lathe in which the work piece is automatically fed and removed without use of an operator. It requires very less attention after the setup has been made and the machine loaded.

CONTINUE… Once tools are set and the machine is started it performs automatically all the operations to finish the job. After the job is complete, the machine will continue to repeat the cycles producing identical parts. An operator can maintain five or six such a types of lathes at a time simply look after the general maintenance of the machine and cutting tools.

Turret Lathe :- Turret lathe is the adaptation of the engine lathe where the tail stock is replaced by a turret slide(cylindrical or hexagonal). Tool post of the engine lathe is replaced by a square cross slide which can hold four tools.

CONTINUE… It has heavier construction and provides wider range of speeds. The saddle carrying the turret head moves along the whole length of the bed. Much longer jobs can be machined. Turret head directly mounted on the saddle. The front tool post can carry 4 tools and rear tool post may have 1 or 2 tools. Turret may have4 to 6 tools. More than one tool may be set to operate simultaneously. There is no lead screw.

Computer Controlled Lathe :- A highly automated lathe, where both cutting, loading, tool changing, and part unloading are automatically controlled by computer coding. E.g. CNC Lathe M/C.(Computer Numerical Control Machine)

CNC LATHE M/C

LATHE MACHINE

Shear Pins and Slip Clutches VARIOUS PARTS OF LATHE Lathe Bed Head Stock Quick change gear box Carriage Cross Slide Apron Tail Stock Automatic Feed Lever Feed of an Engine Lathe Shear Pins and Slip Clutches

1.Lathe Bed:- This is heavy rugged casting made to support the working parts of lathe and also guide and align major parts of lathe. Made to support working parts of lathe. On top section are machined ways. Guide and align major parts of lathe.

2. Head Stock The headstock houses the main spindle,speed change mechanism, and change gears. The headstock is required to be made as robust as possible due to the cutting forces involved,which can distort a lightly built housing.

Head Stock… Induce harmonic vibrations that will transfer through the work piece, reducing the quality of the finished work piece.

3. Quick change gear box Contains number of different-size gears. Provides feed rod and lead-screw with various speeds for turning and thread-cutting operations. TOP VIEW

CONTINUE… The arrangement which are employed in feed gear boxes to obtain multispindle speeds and different rates of feeds are: Sliding Gear Mechanism Sliding Clutch Mechanism Gear Cone And Tumbler Gear Mechanism Sliding Key Mechanism Combination of any two or more of the above Usually two or three levers must be moved to obtain the desired combination within a given range.

4. Carriage Used to move cutting tool along lathe bed. Consists of three main parts- Saddle ii. Cross-slide iii. Apron

CONTINUE… Movement of entire carriage assembly along the bed provides feed for the tool parallel to the lathe axis. The compound rest can be swivelled on the cross slide in the horizontal plane about vertical axis. To the front of the carriage is attached the apron. It is fastened to the saddle and hangs over the front of the bed. The apron houses the automatic feed mechanism for longitudinal and cross feeds and the split nut for thread cutting.

Mounted on top of saddle. 5. Cross Slide Mounted on top of saddle. Provides manual or automatic cross movement for cutting tool.

6. 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.

7. 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.

CONTINUE… In tail stock jobs of different lengths are provided with quill which can be moved in and out by means of a screw and then locked in position. The movement of the quill is parallel to the lathe axis. The quill has a tapered bore into which is fitted a hardened centre which locates and holds the w/p when turning between centre. This bore may also be used for supporting tools for operations like drilling and reaming.

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

9. Feed of an Engine Lathe Distance carriage will travel in one revolution of spindle. Depends on speed of feed rod or lead screw. Controlled by change gears in quick-change gearbox. Obtains drive from headstock spindle through end gear train. Chart mounted on front of quick-change gearbox indicates various feeds.

10. Shear Pins and Slip Clutches Prevents damage to feed mechanism from overload or sudden torque Shear pins- Made of brass ii. Found on feed rod, lead screw, and end gear train. Spring-loaded slip clutches- i. Found only on feed rods ii. When feed mechanism. overloaded, shear pin will break or slip clutch will slip causing feed to stop.

VIDEO OF ENGINE LATHES PARTS...

CUTTING TOOL

WORK HOLDING DEVICES (a) and (b) Schematic illustrations of a draw-in-type collets. (c) A push-out type collet. (d) Workholding of a part on a face plate.

TYPES OF CHUCK - Forholding cylindrical stock centered. - For facing/center drilling etc. Three Jaw Chuck - This is independent chuck generally has four jaws , which are adjusted individually on the chuck face by means of adjusting screws. Four Jaw Chuck

-Collet chuck is used to hold small work pieces. -Thin jobs can be held by means of magnetic chucks. Magnetic Chuck

DANGERS Don’t touch cutter or chips while machine is running. Make sure work is clamped tightly in chuck or collet. Be careful to stay clear of chuck jaws.

SAFETY All lathe operators must be constantly aware of the safety. Handle sharp cutters, centres, and drills with care. Remove chuck keys and wrenches before operating. Always wear protective eye protection. Always stop the lathe before making adjustments. Know where the emergency stop is before operating the lathe. Correct dress is important, remove rings and watches. Do not change spindle speeds until the lathe comes to a complete stop.

CARE AND MAINTENANCE OF LATHE Lathes are highly accurate machine tools designed to operate around the clock if properly operated and maintained. Lathes must be lubricated and checked for adjustment before operation. Improper lubrication or loose nuts and bolts can cause excessive wear and dangerous operating conditions.

CONCLUSION Lathes are normally robust in construction and they will, with good care, last for many years. It is not unusual for instance to see good lathes still in uses that are 50 years old. To ensure good, accurate, trouble free use it is necessary that the correct maintenance routines are regularly carried out and that important surfaces such as slide-ways are kept well protected so as to reduce wear and thus maintain good accuracy, and the lubricants used, are all factors that require your attention.

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