WHAT IS TORQUE?
Torque, by definition, is the result of a force applied to an object through a lever arm, thus tending to rotate the object.
T= F x L
T -- Torque
F -- Applied Force
L -- Lever length measured from the center of rotation to, and at 90" to, the direction of force.
Since both force and length can be expressed in many different units of measurements, so can torque. However, the most common units are: Inch pound (in-lb. or lb.-in), foot pound (ft-lb. or lb.-ft), meter kilogram (mkg) and Newton meter (N·m).
When torque is applied to a threaded fastener, it produces a clamping force that holds the components together. Too much force, and the fastener will break. Not enough, and the assembly will not stay together. By controlling the amount of torque, the clamping or holding force is controlled.
WHY IS TORQUE IMPORTANT?
SAFETY: Bolts or nuts which are not tightened enough may vibrate loose, while over tightened ones may break.
ECONOMY: Improperly tightened components may cause damage or accelerated wear. "Blown out" gaskets and broken head bolts are typical examples of such costly errors.
PERFORMANCE: Today's equipment is made of many precision parts which need to be assembled just right to achieve maximum efficiency and performance. Improperly tightened head bolts may result in poor compression, over tightened bearings may bind, etc.
GENERAL CONVERSION TABLE FOR TORQUE UNITS