DIY Torque Wrench Calibration

What You'll Need
Torque Wrench
20 pound weight

Torque wrench calibration should be done every once in a while in order to ensure its accuracy and effectiveness. An un-calibrated torque wrench can cause certain dangers in your home and car because of the incorrect information that it gives you. You therefore need to calibrate your torque wrench, especially if you will be using it soon to maintain your home or vehicle.

Step 1: Measure the Pressure Point

To start the torque wrench calibration, get your wrench and mark the middle of the back of the head with a marker or pencil. Then, determine at which part of the wrench you apply the most pressure. You should actually simulate this first so you will know the exact point as to where you put pressure. Once you’ve determined this, measure the distance from the point at the middle of the head to the exact pressure point. If your torque wrench measures in inch-pounds, note down the distance in inches. If it measures in foot-pounds, note it down in feet. Label this “distance 1.”

Step 2: Utilize the Weights

Get the vise and clamp the wrench down in a horizontal position. Hang the 20-pound weight by its handle using a sturdy string for your torque wrench calibration. Slide the string with the weight across the handle until the wrench gives you a reading of 40 foot-pounds. The equivalent of this is 480-inch-pounds. Measure and note down the distance from the mark on the center of the wrench head until the string and label this “distance 2.”

Step 3: Determine Calibration Ratio

Get a calculator and determine the calibration ratio. This can be done be dividing distance 2 by distance 1 for the torque wrench calibration. By obtaining this ratio, you will now know the difference between the current settings of your wrench to the actual force it takes to obtain a “click” at that particular setting.

Step 4: Set the Torque Wrench

The torque wrench can now be set for a particular function such as tightening a bolt at home. Simply multiply the needed torque of the bolt to the calibration ratio that you obtained earlier. For example, if the bolt requires 48 foot-pounds of torque and the calibration ratio is 1.115, then the torque wrench calibration is set at 53.52.

Step 5: Other Testing

With your torque wrench already calibrated, try to test its effectiveness by using it in other applications. For example, you can use it in the maintenance of your vehicle or in various home remedies. Check if the bolts that the wrench tightens are properly tightened and that they are not too tight or too loose. You can also counter-check the calibration and accuracy of your lens by using another newly calibrated lens (not by you) and compare the results on the bolts both wrenches have tightened.

Step 6: Storing

In order for the torque wrench to maintain its proper calibration, keep it clean and lubricated at all times. This will prolong its life. More importantly, always set the setting to zero so as not to exhaust the spring so you won’t need a torque wrench calibration session every time you take it out.