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Machining

Machining. Machining is the process of removing the excess material from the work piece in the form of chips, by forcing a cutting tool with one or more cutting edges. Machine tool is a power driven machine to perform machining. A machine tool performs three major functions;

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Machining

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  1. Machining • Machining is the process of removing the excess material from the work piece in the form of chips, by forcing a cutting tool with one or more cutting edges. • Machine tool is a power driven machine to perform machining. A machine tool performs three major functions; (i) It rigidly supports the work piece and the cutting tool. (ii) It provides relative motion between the work piece and the cutting tool (iii) It provides a range of speeds & feeds. P R Venkatesh, Mech Dept, RVCE, B'lore

  2. Machining • Generally, machine tools produce either cylindrical or flat surfaces. • The most commonly used machine tools are; • Lathe • Drilling Machine • Shaping Machine • Planing Machine • Milling Machine • Grinding machine P R Venkatesh, Mech Dept, RVCE, B'lore

  3. Lathe • It is a machine tool which holds the work in a holding device and rotating it against a suitable cutting tool to remove the excess metal from the work. • If the tool is moved parallel to the axis of rotation of the work, a cylindrical surface is produced. • If the tool is moved perpendicular to the axis of rotation of the work, a flat surface is produced. • Lathes are classified as; • Bench Lathe (ii) Speed lathe (iii) Engine Lathe (iv) Tool room lathe (v) Capstan & Turret lathe (vi) Automatic lathe (vii) Special purpose lathe P R Venkatesh, Mech Dept, RVCE, B'lore

  4. Bench Lathe P R Venkatesh, Mech Dept, RVCE, B'lore

  5. Speed Lathe P R Venkatesh, Mech Dept, RVCE, B'lore

  6. Engine Lathe (or) Center Lathe P R Venkatesh, Mech Dept, RVCE, B'lore

  7. Tool Room Lathe P R Venkatesh, Mech Dept, RVCE, B'lore

  8. Capstan & Turret Lathe P R Venkatesh, Mech Dept, RVCE, B'lore

  9. Automatic Lathe P R Venkatesh, Mech Dept, RVCE, B'lore

  10. Special Purpose Lathe P R Venkatesh, Mech Dept, RVCE, B'lore

  11. Lathe Specifications P R Venkatesh, Mech Dept, RVCE, B'lore

  12. Lathe Specifications The size of a lathe is specified by the following: • Maximum diameter of the work piece that can be revolved over the lathe bed. It is also called as height of centers above the lathe bed Or Swing diameter over lathe bed. • Maximum diameter and width of the work piece that can swing when the lathe has a gap bed. • Maximum length of work piece that can be mounted between centers • Overall length of bed: It is the total length of the lathe itself. • Maximum number of speeds & feeds available. P R Venkatesh, Mech Dept, RVCE, B'lore

  13. P R Venkatesh, Mech Dept, RVCE, B'lore

  14. Major parts of a Lathe & their functions The major parts of a lathe are: • Bed • Headstock • Tailstock • Carriage • Feed rod • Lead screw P R Venkatesh, Mech Dept, RVCE, B'lore

  15. Major parts of a Lathe & their functions • Bed: • The lathe bed forms the support for all other parts. • At the top of the bed, precision machined guide ways (inner & outer) are present. • The headstock & tailstock are mounted on the inner ways which keep them perfectly aligned with each other. • The outer ways guide the movement of carriage assembly. • Bed is usually made of grey cast iron because of its good damping property and lowfrictional resistance. P R Venkatesh, Mech Dept, RVCE, B'lore

  16. Lathe Bed P R Venkatesh, Mech Dept, RVCE, B'lore

  17. Major parts of a Lathe & their functions 2. Headstock • Headstock is a box like casting mounted at the left end of the machine. • It consists of a spindle and gear box to rotates the spindle at different speeds. • The spindle has external threads to receive a work holding device such as a chuck or face plate. • The gear box distributes power to the feed rod and lead screw for turning or thread cutting operation. P R Venkatesh, Mech Dept, RVCE, B'lore

  18. Headstock P R Venkatesh, Mech Dept, RVCE, B'lore

  19. Major parts of a Lathe & their functions 3. Tailstock • Tailstock is mounted at the right end of the machine. • It may be slided on the guide ways to support different lengths of work pieces between centers and clamped to bed at any desired location. • It carries a dead center or revolving center. • Tailstock can be offset for taper turning. It can also carry tools like drill bit, reamer, tap, etc. P R Venkatesh, Mech Dept, RVCE, B'lore

  20. Tailstock P R Venkatesh, Mech Dept, RVCE, B'lore

  21. Major parts of a Lathe & their functions 4. Carriage Assembly • It supports and feeds the cutting tool against the work during operation of the lathe. • The carriage slides along the outer guide ways and consists of the following parts; (i) Saddle (ii) Cross slide (iii) Compound slide (iv) Tool post (v) Apron P R Venkatesh, Mech Dept, RVCE, B'lore

  22. Carriage Assembly P R Venkatesh, Mech Dept, RVCE, B'lore

  23. Major parts of a Lathe & their functions (i) Saddle : It is a H-shaped casting that slides over the outer guide ways and serves as a base for the cross slide. P R Venkatesh, Mech Dept, RVCE, B'lore

  24. Major parts of a Lathe & their functions (ii) Cross slide: It is mounted on the saddle and enables the movement of the cutting tool laterally across the lathe bed by means of a cross feed hand wheel. P R Venkatesh, Mech Dept, RVCE, B'lore

  25. Major parts of a Lathe & their functions (iii) Compound rest: It is mounted on the top of the cross slide and supports the tool post. It can be swiveled to any angle to facilitate taper turning & threading operations. P R Venkatesh, Mech Dept, RVCE, B'lore

  26. Major parts of a Lathe & their functions (iv) Tool Post It is mounted on the top of the compound rest and carries the cutting tool. P R Venkatesh, Mech Dept, RVCE, B'lore

  27. Major parts of a Lathe & their functions (v) Apron: The portion of the carriage that extends in front of the lathe is called an apron. It houses feed mechanisms. It contains pinion which engages with the rack for longitudinal feed. P R Venkatesh, Mech Dept, RVCE, B'lore

  28. Major parts of a Lathe & their functions 6. Feed Rod: The feed rod is a long shaft used to drive the apron mechanism for cross & longitudinal power feed during turning, boring & facing operations. The feed rod is powered by a set of gears from the headstock. P R Venkatesh, Mech Dept, RVCE, B'lore

  29. Major parts of a Lathe & their functions 5. Lead Screw: It is a long threaded shaft geared to the headstock. Closing a split nut around the lead screw engages it with the carriage. It used only for thread cutting operations. P R Venkatesh, Mech Dept, RVCE, B'lore

  30. Lathe Operations The most common operations performed on a lathe are: • Turning • Facing • Parting • Grooving • Knurling • Drilling • Boring • Taper turning • Thread cutting P R Venkatesh, Mech Dept, RVCE, B'lore

  31. Turning or Plain Turning: P R Venkatesh, Mech Dept, RVCE, B'lore

  32. Turning or Plain Turning: • Plain turning is a lathe operation to remove excess material from the workpiece & to produce cylindrical surface. • Using the cross slide the cutting tool is first adjusted for desired depth of cut. • As the workpiece revolves, the tool is fed against the workpiece in a direction parallel to the axis of the spindle. P R Venkatesh, Mech Dept, RVCE, B'lore

  33. Plain turning animation P R Venkatesh, Mech Dept, RVCE, B'lore

  34. Facing Operation P R Venkatesh, Mech Dept, RVCE, B'lore

  35. Facing: • Facing is a lathe operation to produce a flat surface normal to the axis of rotation of the spindle. • During facing, the carriage is locked to the lathe bed to prevent its movement. • Using cross slide the cutting tool is fed at right angles to the axis of the work piece. P R Venkatesh, Mech Dept, RVCE, B'lore

  36. Parting off & Grooving P R Venkatesh, Mech Dept, RVCE, B'lore

  37. Parting & Grooving: • Parting or cutting off is the operation of separating a piece of finished work from the bar stock. It is done with a narrow cutting tool called Parting tool. • Grooving or necking is the operation of reducing the diameter of the workpiece over a narrow surface. It is done by feeding a form tool or parting tool into the work using cross slide. P R Venkatesh, Mech Dept, RVCE, B'lore

  38. Parting off & Grooving P R Venkatesh, Mech Dept, RVCE, B'lore

  39. Knurling P R Venkatesh, Mech Dept, RVCE, B'lore

  40. Knurling • Knurling is the process of embossing a diamond shaped pattern on the surface of the workpiece by the use of revolving hardened steel wheels pressed against the work. • Knurling is done to provide grip on handles, screw heads and other cylindrical parts to be gripped by hand. P R Venkatesh, Mech Dept, RVCE, B'lore

  41. Knurling Tool Knurled surface P R Venkatesh, Mech Dept, RVCE, B'lore

  42. Drilling P R Venkatesh, Mech Dept, RVCE, B'lore

  43. Drilling • Drilling is an operation of producing cylindrical hole by means of a cutting tool called drill. • A drill it is placed in the tapered hole of a tailstock sleeve and is fed into the work by rotating the hand wheel of the tailstock. Twist Drill P R Venkatesh, Mech Dept, RVCE, B'lore

  44. Boring P R Venkatesh, Mech Dept, RVCE, B'lore

  45. Boring in Lathe P R Venkatesh, Mech Dept, RVCE, B'lore

  46. Boring • Boring is an operation of enlarging a hole previously drilled with the help of a boring tool. • As in turning, the depth of cut is adjusted by the cross slide and the feed is obtained by carriage movement. Boring Bar P R Venkatesh, Mech Dept, RVCE, B'lore

  47. Taper Turning • Taper turning is an operation on a lathe to produce conical surface on work pieces. • Taper on a lathe is the difference between the diameters over a length. • If ‘D’ is the larger diameter & ‘d’ the smaller diameter, l is the length between the two diameters, then Taper (or) Conicity = (D-d)/ l P R Venkatesh, Mech Dept, RVCE, B'lore

  48. Taper Turning Methods • A taper may be turned by any one of the following methods. • By form tool • By swiveling the compound rest • By Tailstock off set method • By using Taper turning attachment P R Venkatesh, Mech Dept, RVCE, B'lore

  49. Taper Turning using form tool • Here a form tool which has a straight edge set at the desired angle is used. • Theangle between the cutting edge and the axis of the spindle equals half taper angle. • This method is limited to short tapers & is mainly used for chamfering. P R Venkatesh, Mech Dept, RVCE, B'lore

  50. Taper Turning swiveling the compound rest • The compound rest may be swiveled & clamped at any desired half angle of taper on a circular base graduated in degrees. • The tool is fed by rotating the compound slide screw. • This is also limited to short tapers as the movement of the compound slide screw is limited. P R Venkatesh, Mech Dept, RVCE, B'lore

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