Torque

Torque, abbreviated as \(\tau\) (Greek symbol tau) or T, also called moment of force, is a rotational moment.  It is a measure of how much twisting is applied to a fastener.  The units used to measure torque are in the form of force times length.  Usually measured in newton-metres (Nm) if metric units are used or pounds feet (lb-ft) when imperial units are used.

 

Torque formulas

\(\large{ \tau = r \; F \; sin \; \theta  }\)
\(\large{ \tau = l \; F }\)
\(\large{ \tau = d \; F }\)
\(\large{ \tau = I \; \alpha }\)
\(\large{ \tau = \frac{ 5252\; HP }{ s }   }\)	(engine horsepower)

Where:

\(\large{ \tau }\)  (Greek symbol tau) = torque

\(\large{ \theta }\)  (Greek symbol theta) = angle

\(\large{ \alpha }\)  (Greek symbol alpha) = angular acceleration

\(\large{ d }\) = diplacement

\(\large{ F }\) = force

\(\large{ HP }\) = horsepower

\(\large{ l }\) = length, moment arm

\(\large{ I }\) = moment of inertia

\(\large{ P }\) = power

\(\large{ r }\) = radius

\(\large{ s }\) = speed (rpm)

 

Breakaway Torque

The torque necessary to put into reverse rotation a bolt that has not been tightened.

 

Breakloose Torque

The torque required to effect reverse rotation when a pre-stressed threaded assembly is loosened.