Torque Wrench: What Is It For and How Is It Used?

What Is a Torque Wrench?

As mentioned in the introductory paragraph of this article, torque wrenches are precision instruments that guarantee reliable and quality tightening. Used especially to secure industrial production mechanisms, from industrial machines to automobiles to household appliances, these tools allow not to damage the bolt and, at the same time, screw the screw sufficiently. Their use is indeed fundamental to avoid breakages or deteriorations to the various parts in play in the locking. The use of the torque wrench thus allows the homogeneity of the load regarding the mechanical part assembled by different bolted unions.

How Is the Torque Wrench Used?

The correct use of the torque wrench allows tightening mechanical components without the risk of damaging the threads. To better understand the operation of the torque wrench, below we report all the steps to perform (step by step) and all the useful information to know, creating a practical guide to the tightening of bolts.

• The first fundamental data to know before getting to work is the torque value, measured in Newton – Meter (N.m) and which therefore indicates the force that can be applied to the element. The value of the torque is generally indicated on the package of the elements, on the documentation provided by the manufacturer, or can be obtained by measuring the diameter of the part.
  
  
• Once this value has been obtained, the wrench can be adjusted by choosing the socket suitable for tightening the screw or nut. The precision instrument must then be rotated, following the graduated scale reported on the handle.
  
  
• The wrench is characterized by a robust spring that will then be preloaded based on the chosen tightening settings.
  
  
• When the tool is preloaded and housed on the component, you can proceed with the tightening by rotating the wrench.
  
  
• Thanks to the control mechanism present on the wrench, it will signal the reaching of the set torque value, through a real click. At this point, it is possible to remove the wrench and proceed with the fixing of the other screws.
  
  
• Once the fixing of all the screws is completed, it is necessary to unload the tool, bringing the tightening value back to zero. The advice is always to unload the wrench before storing it so as to avoid that, over a long time, it may be damaged and falsify the torque value.

Choosing the Right Torque Wrench

Based on the tightening to be performed and, therefore, the parts to be assembled, it is possible to choose and distinguish between different types of torque wrenches. In general, we can distinguish between two main types, defined by the DIN EN ISO 6789 standard:

• Direct reading or Indication torque wrenches: also defined as digital wrenches, they indicate the detected torque value through an electronic display. They are instruments used in production.
• Click torque wrench: they are tools similar to a ratchet and much more widespread than the first version. They are used with interchangeable sockets based on the diameter of the part to be tightened.

The most suitable choice must be made based on the required use. It is important to emphasize that, in order to guarantee an optimal application, the wrench must be chosen based on an average of its adjustment range, so neither close to its minimum nor to its maximum.

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