Torque Control 3
In most situations there’s a relatively simple relationship between the torque applied to the bolt or nut and the tension created in it. Usually this relationship is linear. For such cases, the following equation is applicable:
Torque = K x d x F
where
K = Nut Factor (dimensionless)
d = Nominal Bolt Diameter (in., mm, etc.) F = Bolt Tension (lbs., N)
F = 75% of bolt material proofload for standard bolts
F= 90% of bolt material proofload for special applications; such as structural bolts
Depending on inputs, the output torque will be given in inch-pounds, foot-pounds, or Newton-meters. This equation implies a linear elastic zone of the torque verses angle-tightening curve. For most of our
common fastening material we know the engineering values of the first two variables. The problem with this equation is with K.
