The pitch of the threaded shaft of the C clamp is p = 0.05 in, and the mean radius of the...

The pitch of the threaded shaft of the C clamp is p = 0.05 in, and the mean radius of the thread is r = 0.15 in. The coefficients of friction between the threaded shaft and the mating collar are μs = 0.18 and μk = 0.16.

(a) What maximum couple must be applied to the shaft to exert a 30-lb force on the clamped object?

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(b) If a 30-lb force is exerted on the clamped object, what couple must be applied to the shaft to begin loosening the clamp?