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Unite-II LATHE

Go to http://tkckt.weebly.com. Unite-II LATHE. Unit II

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Unite-II LATHE

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  1. Go to http://tkckt.weebly.com Unite-II LATHE Unit II Lathe: Introduction, type, construction of simple lathe, mechanism and attachments for various operations, machine specifications, basis for selection of cutting speed, feed and depth of cut, time estimation for turning operations such as facing, step turning, taper turning, threading, knurling. [8 Hrs.] Two Question (i.e. 26 Marks) Numerical of 7 to 8 Theory of 17 to 26

  2. Introduction • A lathe is a machine tool which spins a block of material to perform various operations For more presentation Go to http://tkckt.weebly.com

  3. For more presentation Go to http://tkckt.weebly.com

  4. Introduction • Lathe is a machine, which removes the metal from a piece of work to the required shape & size • operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the work-piece to create an object which has symmetry about an axis of rotation.

  5. Turning Parameters • Forces in turning • Cutting force: acts downward on the tool tip • Thrust force: acts in the longitudinal direction • Radial force: acts in the radial direction • Roughing and Finishing Cuts • Rough cut: high speed cut with little regard for dimensional tolerance • Finishing cut: lower feed rate and depth of cut • Tool Materials, Feeds, and Cutting Speeds • See table 22.4 • Cutting Fluids • See table 22.5

  6. History The origin of turning dates to around 1300BC when the Egyptians first developed a two-person lathe. One person would turn the wood work piece with a rope while the other used a sharp tool to cut shapes in the wood The Romans improved the Egyptian design with the addition of a turning bow. Early bow lathes were also developed and used in Germany, France and Britain.

  7. History • In the Middle Ages a pedal replaced hand-operated turning, freeing both the craftsman's hands to hold the woodturning tools. • The pedal was usually connected to a pole, often a straight-grained sapling. The system today is called the "spring pole" lathe ( Pole-lathe).

  8. History • During the industrial revolution, mechanized power was applied to the lathe via steam engines and line shafting, allowing faster and easier work. • Between the late 19th and mid 20th centuries, individual electric motors at each lathe replaced line shafting as the power source. • Beginning in the 1950s, servomechanisms were applied to the control of lathes and other machine tools via numerical control (NC),

  9. Machine Classification • Size designation • Swing - maximum diameter that can be rotated on the lathe • 2x’s distance from spindle center line to ways • Maximum distance between centers

  10. Size of Lathe Swing Workpiece Length

  11. Size of Lathe .. Example: 300 - 1500 Lathe • Maximum Diameter of Workpiece that can be machined = SWING (= 300 mm) • Maximum Length of Workpiece that can be held between Centers (=1500 mm)

  12. Types of Lathes • Speed • Simple construction of a head stock and tail stock with a tool post. Used for wood turning, metal polishing, or metal spinning.1200-3600rpm • Engine • Most frequently used lathe • Heavy duty • power drive for most tool movements • Size range 12”x24” to 24”x48” - can be larger • Bench Lathe • A bench top model usually of low power used to make precision machine small work pieces

  13. Types of Lathes • Tool room • Greater accuracy • More versatility • Wider range of speeds and feeds • Turret • Hex turret replaces tailstock • Multiple tools set to machine part • High production rates • Still may require some operator skill

  14. Turret Lathes • Capable of performing multiple cutting operations on the same workpiece • Turning • Boring • Drilling • Thread cutting • Facing • Turret lathes are very versatile • Types of turret lathes • Ram-type: ram slides in a separate base on the saddle • Saddle type: • more heavily constructed • Used to machine large workpeiceces

  15. Types of Lathes • Automatic • Similar to turret • A lathe in which the work piece is automatically fed and removed without use of an operator. • Cutting operations are automatically controlled by sequencer of some form • Capable of simultaneous cuts • Can be a cam controlled mechanism • Can be single spindle or multiple spindle

  16. Types of Lathes • Tracer • Hydraulic attachment used to copy the shape of a part from a master. • lathe that has the ability to follow a template to copy a shape or contour. • Machine tools with attachments • Capable of turning parts with various contours • A tracer finger follows the template and guides the cutting tool

  17. Types of Lathes • CNC • Computer controlled • Wide variety of process capability • multiple axis • Indexing and contouring head • On- line and off- line programming available • Computer Numerical Controls (CNC) • Equipped with one or more turrets • Each turret is equipped with a variety of tools • Performs several operations on different surfaces of the work piece

  18. Computer Numerically Controlled Lathes Fig : A computer numerical control lathe. Note the two turrets on this machine.

  19. Component Description

  20. Lathe Basics Spindle Nose Tailstock Spindle Clamp Tool Post Compound Rest HEADSTOCK TAILSTOCK Saddle Feed Change Lever Feed Reverse Lever Lead Screw BED WAYS APRON Bed Gear Box Half Nut Lever Friction-clutch Control Carriage Hand Wheel Motor Drive Cross Slide

  21. Lathe Drive Mechanism Belts are moved from pulley to pulley to change speeds (rpm). Pulley System without back gear: 4 High range speeds Pulley System with back gear: 4 Low range speeds

  22. Carriage Feed A. Longitudinal Feed or “Turning” - The tool is fed along the work. C. Cross Feed or “Facing” – The tool is fed across the work.

  23. Carriage Feed Power Feed for: Turning Facing Used for greater control and accuracy. Speed controlled by the “Quick Change Gear Box”

  24. Carriage and Apron The controls on the carriage and apron control all the tool and carriage movement.

  25. Lathe Carriage and Apron Tool Post Compound Rest Carriage Lock Screw Cross Feed Knob Cross Slide Apron Hand Wheel Apron Feed Change Lever Half Nut Lever Power Feed Clutch Compound Rest Knob

  26. Carriage and Apron Apron Hand-wheel: Turning Cross-feed knob: Facing Apron Feed-change lever: Selects power feed between turning and facing Power Feed Clutch: Engages the power feed

  27. Apron Hand Wheel Used to move tool along the work - for Turning (Longitudinal Feed) Apron Hand Wheel

  28. Cross Feed Knob Used to move cutting tool across the end of the stock - Facing (Cross Feed) Cross Feed Knob

  29. Power Feed Clutch Engages the power feed for turning or facing operations Power Feed Clutch

  30. Apron Feed Change Lever Switches power feed between turning and facing directions Apron Feed Change Lever

  31. Chuck Three Jaw Chuck - For holding cylindrical stock centered. - For facing/center drilling the end of your aluminum stock

  32. 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 • Collet chuck

  33. Work Holding Devices Fig : (a) and (b) Schematic illustrations of a draw-in-type collets. The workpiece is placed in the collet hole, and the conical surfaces of the collet are forced inward by pulling it with a draw bar into the sleeve. (c) A push-out type collet. (d) Workholding of a part on a face plate.

  34. Three jaw chuck - For holding cylindrical stock centered. - For facing/center drilling the end of your aluminum stock Four-Jaw Chuck - This is independent chuck generally has four jaws , which are adjusted individually on the chuck face by means of adjusting screws

  35. Collet Chuck Collet chuck is used to hold small workpieces • Thin jobs can be held by means of magnetic chucks. Magnetic Chuck Thin jobs can be held by means of magnetic chucks. For more presentation Go to http://tkckt.weebly.com

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

  37. Three-jaw Universal Chuck

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

  39. Four-Jaw Independent Chucks

  40. Headstock Spindle Types • Threaded spindle nose • Screws on in a clockwise direction • Tapered spindle nose • Held by lock nut that tightens on chuck • Cam-lock spindle nose • Held by tightening cam-locks using T-wrench • Chuck aligned by taper on spindle nose

  41. Threaded Spindle Nose

  42. Tapered Spindle Nose

  43. Cam Lock Spindle Nose

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

  45. Spring Collet Chucks • Spring-collet chuck • One form: Handwheel draws collet into tapered adapter • Another form: Uses chuck wrench to tighten collet on workpiece • Can hold larger work than draw-in type

  46. | Spring Collet Chucks

  47. Spring Collet Chucks

  48. Jacobs Collet Chuck • Jacobs collet chuck • Utilizes impact-tightening handwheel to close collets • Wider range than spring-collet chuck

  49. Jacobs Collet Chuck

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