1. MECHANICS OF METAL CUTTING

3. Elements of Metal Cutting

4. Heat Generation Zones (Dependent on sharpness of tool) (Dependent on  ) (Dependent on  10% 30% 60%

5. Tool Terminology Side relief angle Side cutting edge angle (SCEA) Clearance or end relief angle Back Rake (BR),+ Side Rake (SR), + End Cutting edge angle (ECEA) Nose Radius Turning Cutting edge Facing Cutting edge

6. Cutting Geometry

8. Material Removal Rate

9. Cutting Models ORTHOGONAL GEOMETRY OBLIQUE GEOMETRY Tool workpiece Tool workpiece

11. Orthogonal Cutting

12. ‘ Turning’ Forces For Orthogonal Model End view section 'A'-'A' Note: For the 2D Orthogonal Mechanistic Model we will ignore the radial component F t 'A' 'A' c F

13. ‘ Facing’ Forces For Orthogonal Model End view Note: For the 2D Orthogonal Mechanistic Model we will ignore the Longitudinal component

15. Orthogonal Cutting Model (Simple 2D mechanistic model) Mechanism: Chips produced by the shearing process along the shear plane  t 0  + Rake Angle Chip Workpiece Clearance Angle Shear Angle depth of cut Chip thickness Tool Velocity V tool t c

16. tool Cutting Ratio (or chip thicknes ratio)  t c t o  A B Chip Workpiece

17. Experimental Determination of Cutting Ratio Shear angle  may be obtained either from photo-micrographs or assume volume continuity (no chip density change): i.e. Measure length of chips (easier than thickness) w t L 0 0 0 w c L c c t

18. Shear Plane Length and Angle  or make an assumption, such as  adjusts to minimize cutting force: (Merchant)  t c t o  A B Chip tool Workpiece

19. Velocities (2D Orthogonal Model) Velocity Diagram (Chip relative to workpiece) V = Chip Velocity (Chip relative to tool) Tool Workpiece Chip V = Cutting Velocity (Tool relative to workpiece) Shear Velocity c     V s V V s V c

20. Cutting Forces ( 2D Orthogonal Cutting) Free Body Diagram Generally we know: Tool geometry & type Workpiece material and we wish to know: F = Cutting Force F = Thrust Force F = Friction Force N = Normal Force F = Shear Force F = Force Normal to Shear c t s n Tool Workpiece Chip Dynamometer R R R R F c F t  s F F n N F

21. Force Circle Diagram (Merchants Circle) R F t F c Tool F N      F s    F n

22. Results from Force Circle Diagram (Merchant's Circle)

24. Stresses On the Shear plane: On the tool rake face:

26. Material Removal Rate (MRR)

27. Specific Cutting Energy (or Unit Power) Energy required to remove a unit volume of material (often quoted as a function of workpiece material, tool and process:

28. Specific Cutting Energy Decomposition 1. Shear Energy/unit volume (Us) (required for deformation in shear zone) 2. Friction Energy/unit volume (Uf) (expended as chip slides along rake face) 3. Chip curl energy/unit volume (Uc) (expended in curling the chip) 4. Kinetic Energy/unit volume (Um) (required to accelerate chip)

29. Specific Cutting Energy Relationship to Shear strength of Material SHEAR ENERGY / UNIT VOLUME FRICTION ENERGY / UNIT VOLUME APPROXIMATE TOTAL SPECIFIC CUTTING ENERGY

30. Relation between Pressure and Cutting velocity

31. Effect of Rake angle on Cutting Force

32. Average Unit Horsepower Values of Energy per unit volume