How to Calibrate a Torque Wrench

By Richard S. Clark | Last Updated: February 18, 2022

Calibrating the torque wrench will lead to the production of quality results. It is the documented comparison of measurements device against another reference device. In essence, the calibrator is more accurate than the one you are torque wrench.

How then does one calibrate? What is the importance of doing so? Does it serve any purpose? In this article, I will answer all the above questions, including any other that you need to know. I shall take you through all the steps of accomplishing the task to equip you with the knowledge on the work. Please read through for more information.

What are the requirements for torque wrench calibration?

  • To perform the task, you will require the following tools and supplements:
  • A tape measure, preferably yellow. I would always advise you to use such a tape measure to gauge the torque wrench.
  • The safety-toe shoes.
  • A bench secured with a vise or even a lug nut that you attach to equipment.
  • A booklet and a pen to note down the calculations.
  • A clicker style torque wrench.
  • A strong string having a weight/load rating that can hold the weight.
  • A twenty to thirty-five-pound weight.

The procedure of calibrating

  1. Take the measurement.

Whenever you measure the torque wrench, start from the middle of the square drive. That is the point of attaching the socket. Where possible, apply the full inches in comparison with the partial ones to make the calculations. On the handle, mark the point to stop the measurement. Get a permanent marker, preferably the black one, to insert the markings. Record all the results that you do on a booklet because you will always need to refer at a later time.

  • Secure the torque wrench.

With the use of a vise, lock the wrench into it. If you do not have one, then you can use a socket instead. Secure it together with the torque wrench on the lug nut or a bolt of equipment. Leave sufficient space for tying a rope and the weight for performing the calibration test. Secure the square end of the torque wrench and do not overtighten it to avoid damaging the drive. Make sure that the handle faces outward to stop hindering the rope as well as the weight. Double-check to ensure that you only clamp the square drive to the vise. It should allow the handle to move without any restriction.

When doing the work on equipment, then it is advisable to bring cardboard behind the torque wrench. It helps avoid damaging the body of the equipment. You will also have to wear protective steel-toe shoes. It helps protect your feet in case any material falls off and comes crushing! You should, however, give way when such incidences happen as it may cause serious bodily harm.

Make the calculations.

The trick to accuracy is to find the distance from the first step by the amount of weight that you will use to obtain the inch-pounds by multiplying. Assuming that you are using a thirty-five-pound weight, then you have to divide that by twelve. It will result in the foot-pounds. Do not forget that the outcome will not be the same if you are using different units of measurements or distances/lengths.

To understand the calculations, we are going to look at the following example:

If you are using a twenty-inch torque wrench and a weight of thirty-five pounds, then:

Twenty inches x 35 pounds­­ will give you 700 inch-pounds.

Dividing it by twelve, that is 700 inch-pounds/twelve will give you 58.33 foot-pounds.

  • Secure the weight and perform calibration checks.

Use either a rope or a cable to tie the weight. Create a loop in the end that can accommodate the handle of the torque wrench with ease. Ensure that you secure the rope at a sufficient distance that the weight will not be in contact with the ground.

Place the wrench at least twenty-five foot-pounds and hang the end of the loop leaving sufficient space to suspend the weight.

Listen to the wrench, and if you hear a single click, then you will need to adjust it to 27-foot pounds. Should it sounds again, then you should make more adjustments. When you get to a point where you hear none, then the torque wrench is already accurate.

  • Make further adjustments.

You can do this by tightening or loosening the spring tension. It is in the center of the wrench or even below the handle. It might be necessary to make loose some parts to find it. Such may also force you to alter the measurements before making any adjustments. Keep in mind that the wrench has to remain set to the foot-pounds from the calculations that you did earlier.

Please note that you can make all these adjustments by yourself. However, if you do not have the capacity, then you should send it to a professional to calibrate it. In the alternative, you can purchase a new one with measurements!

How often should I calibrate a torque wrench?

Just like the regular serving of your automobile, so should the torque wrench calibration be in place. Over time, they undergo wear and tear that can have devastating effects on their interior parts. It may make the fasteners to be loose and hence causing them to dislocate under stress. Alternatively, they may become excessively tight and therefore deforming the wrench or even breaking it.

As a standard practice, you should calibrate it when either of the following events occurs:

  • After every twelve months (one year), or
  • After every five-thousand cycles.

That means you should calibrate it once you achieve any of the above conditions. If you get to 5,000 cycles twice a year, then you should calibrate it two times. Otherwise, you should do it once after one year!

What are the merits of calibrating your tool?

  1. It ensures that you achieve a high level of accuracy when using it.
  2. The practice ensures that you adhere to international standards of operations.
  3. It makes the professionals servicing the wrench to achieve accurate torque applications.
  4. Correct and accurate calibrations help save time and money during the quality control inspection happens.
  5. Regular calibration and servicing help to reduce the risk of malfunctioning during the service! It, thus, help save on time and money in warranty-related issues.

How long does a torque wrench last?

It depends on how you handle and take care of it. If you service it regularly and carry out calibrations as it should be, then it should serve you for about a decade! I would advise you to have more than one for extended useful life!

Any tool or machinery will not have a long life if you do not carry out maintenance as it should be.

What is the cost of calibrating a torque wrench?

The price is variable depending on the weight of the tool. It can also differ depending on the region or location.

Generally, the price would range from $50 to around $200. For rush services, the cost would even be higher, and this will also depend on the weight of the wrench.

Conclusion

A torque wrench requires constant calibration. The recommended cycle for doing it is when twelve months elapses or after every five-thousand cycles. Failure to calibrate it will cause the tool to wear out fast and to have a short useful life! It may also fail to satisfy the quality of the international standards of operations.

Read more guides on the Wrenchview blog.

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