Bolt Torque

Written by Jerry Ratzlaff. Posted in Fastener

Torque, also called "moment of force", is a rotational moment. It is a measure of how much twisting is applied to tighten (turn) the nut on a bolt.  When bolting flanges together or anything else tor that matter, tightening the nut stretches the bolt adding pressure to the gasket.  The bolt are designed to stretch a bit acting like a spring.  Different factors can affect the torque like number of threads, oil, rust, type of material, etc.


\(T = \frac {kdp} {12} \)


\(T\) = torque (ft-lbs)

\(k\) = torque coefficient (dimensionless)

\(d\) = nominal diameter (inches)

\(p\) = desired clamp load tension (lbs)