a) Why is the orthogonal cutting model useful in the analysis of metal machining? (3 marks)
b) An orthogonal cutting operation is performed using a rake angle of 15° and having a chip thickness before the cut = 0.3 mm and width of cut = 2.5 mm. The chip thickness ratio is measured after the cut to be 0.55. Determine the following:
i) The chip thickness after the cut,
ii) The shear angle,
iii) The friction angle,
iv) The coefficient of friction, and
v) The shear strain. (10 marks)
c) What is the main difference between a horizontal milling machine and a vertical milling machine? (2 marks)
d) A face milling operation is used to machine 6.0 mm from the top surface of a rectangular piece of aluminum 300 mm long by 125 mm wide in a single pass. The cutter has four teeth cemented carbide inserts and is 150 mm in diameter. The cutting speed = 2.8 m/s, and chip load = 0.27 mm/tooth. Assuming that the cutter enters the workpiece from its short side and follows a path that is centered over the workpiece, determine:
i) The actual machining time to make the pass across the surface, and
ii) The maximum metal removal rate during cutting. (10 marks)
e) A turning operation is carried out with no coolant and using a cutting speed of 152.4 m/min. The current cutting conditions (dry) result in Taylor tool life equation parameters of n = 0.25 and C = 396.24 (m/min). When a coolant is used in the operation, the cutting speed can be increased by 20% and still maintain the same tool life. Assuming that n does not change with the addition of the coolant, what is the resulting change in the value of C? (5 marks)
