If the required clamping force at the board A is to be F, determine the torque M

Question:

If the required clamping force at the board A is to be F, determine the torque M that must be applied to the handle of the hold-down clamp to tighten it down. The single square-threaded screw has a mean radius r and a lead r1, and the coefficient of static friction is μs.

Given:

F = 70 N

r = 8 mm

rl = 2 mm

μ s = 0.38