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Homework Solutions to Chapter 23

# Homework Solutions to Chapter 23 - Homework Solutions to...

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Homework Solutions to Chapter 23 Review Questions 1. The flutes form the rake angle of the cutting edges, permit coolant to get to the cutting edges, and serve as channels (elevators) through which the chips are lifted out of the hole. 2. The rake angle of the drill is determined by the helix angle of the drill at the outer extremities - the tips - and gradually changes to a zero rake angle at the inner extremities-the chisel edge. 10. The margins bear or rub against the drilled hole and help to guide the drill and prevent it from bending. This rubbing action also produces heat, which expands the drill and increases the rubbing and friction, which can increase the torque. Proper lubrication is advised to reduce the friction at the walls of the hole. 25. First, the geometry of a drill for plastics will be very different than a drill for cast iron. It will have much larger helix angles and therefore larger rakes. Also, plastic is a very poor heat conductor compared to cast iron so the frictional heat will remain in the drill, causing it to overheat. Problems: 3. Cutting speed = 200 fpm N = (12 x 200)1 3.14 x 1.5 = 509 rpm MRR = π D

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