Chapter 8, Problem 27P

From your experience with Prob. 8-26, generalize your solution to develop a turn-of-nut equation

$N_t=\frac{\theta }{360°}=\left(\frac{k_b+k_m}{k_b{k}_m}\right)F_{i}N$

where N_t = turn of the nut, in rotations, from snug tight

θ = turn of the nut in degrees

N = number of thread/in (1/p where p is pitch)

F_i = initial preload

k_b, k_m = spring rates of the bolt and members, respectively

Use this equation to find the relation between torque-wrench setting T and turn-of-nut N_t. (“Snug tight” means the joint has been tightened to perhaps half the intended preload to flatten asperities on the washer faces and the members. Then the nut is loosened and retightened finger tight, and the nut is rotated the number of degrees indicated by the equation. Properly done, the result is competitive with torque wrenching.)