Bolt Torque

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.

Bolt Torque formula

\(\large{ T = \frac {k\;d\;p} {12}  }\)

Where:

\(\large{ T }\) = torque

\(\large{ p }\) = desired clamp load tension

\(\large{ d }\) = nominal diameter

\(\large{ k }\) = torque coefficient (dimensionless)