A DIY Guide to Calibrating a Torque Wrench

A torque wrench is a tool that can measure the tension and twist of nuts and bolts to ensure that they are tight enough without over-tightening them. This instrument looks like a long-armed wrench which bends when you apply the turning force to the handle.

Its handle contains an internal mechanical indicator which is connected to a calibrated scale. You must stop twisting the bolt as soon as the indicator determines that you have reached the desired torque. Just like any other measuring instrument, precise calibration of a torque wrench is important to provide accurate results.

Calibrating a Torque Wrench Yourself

It’s important to calibrate the torque wrench properly to ensure that the fastener has the exact tension it needs to function safely. You can use the calibration services of accredited laboratories to calibrate your torque wrench, but you must also know how to do it yourself.

The following 7 steps will help you with a DIY calibration of a torque wrench:

  • Step 1
  • Measure the length from the square drive to the point of the torque wrench where your hand rests while using the tool.

  • Step 2
  • Secure the wrench by placing the square drive in the vise. Do not lock any other part of the wrench in the vise.

  • Step 3
  • Align the torque wrench to the value of the settings you got in step one (the distance from the square drive to your hand) and multiply it by 20 pounds.

  • Step 4
  • Tie the 20-pound weight with a thin rope to the wrench from the position your hand rests.

  • Step 5
  • It is important that you keep the wrench in a horizontal position during this step. If you hear a click from the wrench, lift the weight and move it towards the head of the wrench until the clicking stops. If you don’t hear a click, then move the weight farther from the head of the wrench and try again. Make a definitive mark after two or three stops in the same location of the wrench.

  • Step 6
  • Measure the distance from the square drive to the location of the rope after step five. Multiply the finding distance by 20 pounds.

  • Step 7
  • Use the formula Ta = Ts x (D1/D2) to calculate the applied torque with your findings, where

    Ta – Applied torque
    Ts – Torque setting
    D1 – Distance measured in step 1
    D2 – Distance measured in step 5

Factors Affecting Calibration

No matter how well you have calibrated your torque wrench, it will lose its accuracy over a period of time. This means that you must constantly calibrate to ensure that it stays accurate and provides you with the perfect results. You must understand the factors that will affect calibration and learn how to make a calibration last longer.

One of the main factors that affect calibration is the average temperature at which the wrench is used. This will determine how accurately the tool is calibrated. Regardless of whether you work with the tool in warm or cold conditions, you must set the measurements of the tool to a comfortable setting, preferably in the climate in which the instrument will be used. This helps in reducing the chances of errors in and provides accurate results.

Make sure that the mathematics is applied correctly to determine the set measurements at which the tool will be used. If any factor is incorrect, you will observe an offset in the calibration, which in turn will cause major errors in results. Ensure that you measure the distance between the square drive and the hand position, at both the times absolutely accurately to make sure that there are no discrepancies in the equation.

When you learn to calibrate the torque wrenches and understand the various factors affecting them, you will be able to correct the performance of the wrench every single time and attain reliable results, thus assuring high quality of the products.

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