What we should know about the torque wrench


The torque wrench is a precision hand tool. This is used to adjust the tightening torque of threaded elements, which is the torque with which a screw or nut must be tightened. If you want to know more about this tool, we will tell you what it is and how a torque wrench works.

This tool is expressed in units of force multiplied by distance (torque), usually in newton-meter (Nm). Depending on the size of the key, normal would be 1/4″, 3/8″ and 1/2″ and will be designed for a specific tightening torque.

What types of torque wrenches are there?

There are several types of torque wrenches, which can be differentiated as follows:

  1. Clock. It consists of a dial type watch, in which you can see the value of the torque measured by a moving needle.
  2. Of jump. A torque wrench consists of a ratchet and a glass. The key has a handle with a mechanism in which the tightening torque is regulated. If you try to push harder than the selected one, jump the mechanism that prevents it.

We can also find a specific type of jump keys. For example, for gas work. They can be used in the adjustment of the counters of the counters, in which open-mouth wrenches are needed. Even so, the operation, in general, does not vary with respect to the normal ones.

  1. Digital. Similar to the jump key, the digital torque wrench has an electronic circuit inside it and, in addition, a screen in which the measured values are displayed. Among other functions, it warns, by means of a sound or vibration, when the pre-set torque is reached. It allows measuring in several different units, such as Nm or KgFm, among others.

Recommendations for using the torque wrench

  • It is an adjustment tool. Due to its mission, the torque wrench is very precise and sensitive so it should not be used to loosen bolts.
  • It should be used with care as if it were any other precision instrument. It must be stored properly after use to avoid shock.
  • When it is not being used or when finishing the work in the mechanical workshop, it is necessary to restore its lowest value so that it is not under pressure.
  • The torque wrench must be used with one hand and a continuous and fluid movement.
  • An extension on the handle should not be used. This would damage the established value when correctly signaled.
  • A torque wrench prevents but does not prevent excessive adjustment. When the required torque is reached, the torque control system of the key will “activate”, and the operator will hear a clear click sound. If you hear this “click” without moving the key at the beginning, it means that the torque application has been adjusted too much. The best practice is to start over: loosen the bolt first, tighten it with an adapted tool and finish with the torque wrench to reach the correct and safe torque.
  • Maintenance of the torque wrench: as it is a high precision tool, it must be recalibrated with some frequency. This recalibration is the responsibility of the user of the tool. A recommendation for its maintenance is the recalibration every year or every 5,000 cycles in an official service of the manufacturer. Undoubtedly, if the torque wrench has suffered a fall or is damaged, it must be sent for inspection.

Finally, remember that you should never retighten by hand a screw that has previously been tightened to the proper torque or use a torque wrench to loosen screws. Also that in cases of not using the key for quite some time, it is advisable to keep it with the minimum possible torque, turning the fist against the hands of the clock until the stop.