Torque wrench is a tightness system, which permits a very accurate fixing regulation of nuts, screws and bolts.
Torque wrench is like the most common ratchet. During the use, the wrench advices the achievement of the set torque producing a strong jerk or through an indicator hand on a graduated scale.
The units of measure are usually kilogram-meter or Newton in meter system, and pound per foot in the imperial system.
Torque wrenches are generally used when the tightening is remarkable in order not to damage the thread, or to ensure the homogeneity of the load in a mechanical part held in place by several screws or bolts.
There are several models and variants of torque wrenches. The main differences are: