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Mt 2 ppt
- 1. PRACTICAL MACHINING OPERATIONS SUBMITTED TO SUBMITTED BY ER. P.S. RAO DEVI LAL ASSISTANT PROFESSOR ME(MT IInd SEM.) DEPTT. OF MECHANICAL ENGINEERING 152208
- 2. PROCESS • 1. TURNING • 2. SHAPING AND PLANING • 3. MILLING • 4. DRILLING
- 3. MILLING • Material removal is achieved by a rotatory cutting tool with a no of cutting teeth rotating about a fixed. • The work-piece is feed pass the cutter and each tooth removes material during interaction with the work-piece.
- 4. Classification of milling operation • 1. plain or peripheral milling • 2. face or end milling • When the cutter velocity during peripheral milling is in the opposite direction is known as conventional or up-milling and when they are in the same sense, the operation is called down milling.
- 5. Continue...
- 6. Undeformed chip-thickness • d= depth of cut • D= cutter diameter • l= chip length then If is the mean chip thickness
- 7. Continue... Then volume of individual chip can be evaluated Equating both then If is the average chip thickness then,
- 8. Continue... • The size of cut depends on the various cutting parameters. • The tool angles in face milling cutters are similar to those on turning tools except that the nomenclature used are different. • When the side cutting- edge angle is also zero, is equal to the radial rake angle.
- 9. Forces • Three type of force longitudinal, vertical and transverse directions respectively. • Dynamometer is used for measurement of forces. • When a straight cutter (helix angle =0) is used, the axial or transverse component is zero
- 10. Continue... • The variation in forces have a damaging effect on tool life as well as surface finish. • When the helix angle is zero, the cutting force increases to a maximum value and rapidly drops to zero. • The forces fluctuations can be reduced by increasing the number of teeth on the cutter.
- 11. Surface finish • The surface generated will also have the feed marks by individual tooth.
- 12. Continue... • Ideal surface roughness in face milling can be obtained from the feed marks left behind by the cutter teeth. • Where s is the feed per tooth. • Similarly in face milling
- 13. Continue... • is the end cutting-edge angle and is the side cutting-edge angle.
- 14. DRILLING • Creates a round hole in a work part • Contrasts with boring which can only enlarge an existing hole • Cutting tool is called a drill or drill bit • Customarily performed on a drill press, but can be done on a vertical mill and on a lathe
- 15. Continue... • f is feed • normal rake angle • Distance varies with • and are the point and helix angles and D is the twist drill diameter.
- 17. Undeformed chip-thickness • Undeformed chip-thickness t and the chip width b can be evaluated as
- 18. Force and power • The drilling force can be resolved into the components , is the tangential component, and the force component normal to the cutting edge. further resolved into two components, the radial component and the thrust component acting axially. • Where and are the tangential components of forces due to friction and extrusion at the chisel edge.
- 20. Continue... • Empirical relations based on experimental results are of the form
- 21. Surface finish • Drilling operations are usually considered as roughing operations and not much concern is shown on the quality of surface finish produced. • For better finish and accuracy. The drilling operation is usually followed by reaming.