The Nuts And Bolts On Torque Wrenches

A wrench that is used to set the torque of a fastening such as a nut or bolt to a great degree of precision is called a torque wrench. It is actually a socket wrench that comes with special internal mechanisms and is of great use where you need to be absolutely sure about the tightness of the screws and the bolts. You can measure how much torque is applied so that you are sure that the tightness is up to the specifications. So, you can ensure that there is proper loading and tension of all the parts. So indirectly, it is measuring bolt tension. However, thanks to the friction between the mating hole and the fastener, this technique does suffer from inaccuracy sometimes. So it is better to measure the bolt tension or the bolt stretch and very often torque is the only measurement that is possible and accurate.

You do get more sophisticated versions where a calibrated clutch mechanism is used. As soon as you get the desired torque, a clutch slips and you prevent over tightening. The most common one uses a ball detent and spring and the spring comes preloaded with an adjustable screw thread and this is calibrated in torque units. This ball detent uses force till you get the desired torque and then the spring is released and the balls clicks out of the socket. There are quite a few variations to this design and you have a whole range of them for various applications and sizes. This design is, in fact, modified and used in drills to prevent the gouging-out of the heads of screws while tightening them.