When servicing some components and assemblies of the car, it is required to tighten the thread with a strictly defined force, which is called the moment of force. A special torque wrench is used to ensure the correct choice of force. Care must be taken when handling this instrument.
How the torque wrench works
The torque wrench resembles a conventional ratchet in appearance, equipped with a special scale designed to determine the required force transmitted to the threaded connection. Depending on the type of instrument, the scale can be in the form of a dial gauge, but it can also be equipped with a digital indicator screen.
In the most common case, the instrument has a scale stamped on the key itself; an indicator of the effort achieved in this case will be a characteristic click. Such a torque wrench has a handle that can rotate, and two scales, where a number of divisions are applied. The main scale is located on the stationary part of the instrument, and the auxiliary scale is located on the rotating handle.
Typically, a torque wrench has a strictly limited range of permissible forces, which is indicated in the technical documentation or in the instructions for the device. The width of the range can also be determined by the limit marks on the main scale of the instrument.
When choosing a key for servicing a car, you should find out in advance what efforts may be required when tightening threaded connections on individual units.
How to use a torque wrench correctly
Let us assume that it is required to tighten a threaded connection with a certain force. First you need to choose a key with a suitable range. A movable handle is screwed onto the base of the tool. It will move along the stationary scale of the instrument. When the handle almost reaches the desired mark on the main scale, you should switch attention to the auxiliary scale and rotate the handle to the mark exactly corresponding to the required force. The key is ready to use.
Now you need to attach a socket of the correct size to the torque wrench, that is, corresponding to the nut. With the subsequent tightening of the nut, at some point the planned effort will be achieved, which will be clear from the characteristic click that the tool will emit. An experienced master can also sense the coming of this moment by changing the effort perceived by the hand.
A click means that the required tightening torque has already been reached, so the process can be terminated.
If you continue to tighten the threaded connection without paying attention to the click, the torque tool will work like a normal wrench, tightening the nut further and making a click. In order for the key to work for a long time, and the connection was not damaged by excessive force, such situations should be avoided. After completely screwing the nut to the desired position, the handle should be returned to its original position by unscrewing it back.