Torque is a turning or twisting force, the result of a force applied at a given distance about a known centre. Torque is recorded in units of force x distance.

Torque wrench is a hand tool used to apply the torque. Torque wrenches are available in different types such as click type, dial type, electronic, torque drivers. Various brands of manufacturers are available in the market. Some of the leading brands are Britool (U.K.), Rahsol (Germany), Snap - On (U.S.A.), Facom (France), Norbar (U.K.), Tohnichi (Japan) etc. In India local brands like Triptork, Torqclick, Torqtool, Mekaster and Tritool are available.

Torque wrench testers are used to verify the accuracy of torque wrenches and the reliability of measurements made by torque wrench. As per IS : 7145, allowed error in calibration is 5%.

Frequency of calibration of torque wrench is to be decided by user depending upon the use. There is no standard available that recommend the frequency of calibration. To overcome the problem of our customer, we have analyzed 3 different calibrated torque wrenches. It has been observed that in the range of 2500 - 2800 repetitions, the observed readings tend to change. So as per our experience we recommend our customers to calibrate the torque wrench after every 2500 repetitions.

If in calibration, the error reported is beyond acceptable limits then is it necessary to scrap that tool?

No, if the error of the torque wrench is found beyond the acceptable limits in the calibration, it needs to be repaired. It is not recommended to use any correction factor. Also if any spare is misplaced or damaged, it can be repaired. It is advisable to replace the torque wrench if the repairing charges are more than 30% of the cost of new torque wrench.