1. Physics of Metal Cutting & Machinability of Metals

2. MACHINABILITY AND CHIP FORMATION
Introduction
Machinability is the relative difficulty of a machining operation with regard to tool life, surface finish, and power consumption.
Softer materials are generally easier to machine than harder ones.

3. Determine how metal cutting affects the surface structures of metals.
OBJECTIVES
After completing this unit, you should be able to …
Determine how metal cutting affects the surface structures of metals.
Analyze chip formation.
Explain machinability and machining behavior of metals.

4. Principles of Metal Cutting
In machining, the tool material rotates or moves in a linear motion or the work-piece rotates or moves.
The moving or rotating tool must be made to move into the work material to cut a chip, a procedure called feed.
The feed controls the thickness of the chip, and the depth of cut is often called in-feed.

5. Machining Principles and Operations

6. Machining Principles and Operations
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Machining Principles and Operations

7. Machining Principles and Operations
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Machining Principles and Operations

8. Machining Principles and Operations
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Machining Principles and Operations

9. Machining Principles and Operations
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Machining Principles and Operations

10. Principles of Metal Cutting
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Principles of Metal Cutting
A common misconception is that the material splits ahead of the tool, which it does not.
The metal is sheared off and does not split ahead of the chip.

11. Principles of Metal Cutting
The metal is forced/deformed in the direction of the cut, the grains are elongated & distorted ahead of the tool and rupture along a shear plane.

12. Principles of Metal Cutting
Chip-Tool Interface

13. Principles of Metal Cutting
Deformed Zone

14. Principles of Metal Cutting
Plastic Flow

15. Principles of Metal Cutting
Rupture

16. Chip Formation Discontinuous Chip Brittle work material
Small rake angle
Feed rate
Low cutting speed (rpm’s)
Machine chatter

17. Chip Formation Continuous Chip Ductile work Feed rate
Cutting tool edge
Large rake angle
High cutting speeds
Temperature
Minimized chip flow resistance

18. Chip Formation

19. Chip Formation Continuous chip w/ built-up edge Affects tool life
Surface finish

20. Temperature & Friction
Plastic Deformation
Chip-tool interface
Tool Life
Surface Finish
Accuracy

21. REVIEW Define Machinability
Name 2 methods by which heat is created during machining.
How does temperature affect machining operations?
What is a built-up edge and what does it affect?
Name two different types of chip formations.
What conditions can create discontinuous chip?
Describe the process of plastic flow during the cutting process.

22. REVIEW
During the cutting process, what is meant by the deformation zone?
What is the chip tool interface?

23. ANY QUESTIONS?