Why do you think the maximum temperature in orthogonal cutting is located at about the middle of the tool–chip interface? (Hint: Note that the two sources of heat are (a) shearing in the primary shear plane and (b) friction at the tool–chip interface.)

To what factors do you attribute the difference in the specific energies in machining the materials shown? Why is there a range of energies for each group of materials?

Comment on your observations regarding the hardness variations shown. Why does the temperature in cutting depend on the cutting speed, feed, and depth of cut? Explain in terms of the relevant process variables.