Q. Determine the Bolt Torque?
The value of the bolt torque, which will give the desired bolt stress, can be calculated from Equation. The friction coefficient (K) is for a well-lubricated bolt and nut.
T = K * SB * d * Ab
Where :
K = 0.2 (friction coefficient)
T = bolt torque (ft-lbs)
SB = desired bolt stress (psi)
d = root diameter of the bolt (in).
Ab = cross-section root area of the bolt (in2)
The calculated torque values will generate the approximate stress values (SB). Tests have shown that the average stress will be within 10% of the desired loading stress after step-wise torquing of well-lubricated and undamaged bolts.