# Bolt Torque

Written by Jerry Ratzlaff on . 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.

## formula

$$T = \frac {kdp} {12}$$

Where:

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

$$k$$ = torque coefficient (dimensionless)

$$d$$ = nominal diameter (inches)

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