A torque wrench is an essential tool for many jobs around the house and around the car. Proper tension on the threads means that a fastener will have the greatest balance of strength and life. However, it can cost up to $100 to get your torque wrench calibration professionally checked. For many, this is impossible to pay regularly, so some use the wrench hoping that everything has stayed in place. You can save the money and the worry by calibrating the torque wrench at home with just a few tools.
- Skill level:
- Moderate
Instructions
Things you need
- Vice
- Pencil and paper
- Ruler or tape measure
- Bailing wire
- Various weights
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1
Put the wrench into the vice and ratchet it until the handle is horizontal. Make sure the vice is touching only the box-shaped portion at the end of the wrench. You need everything else free to adjust.
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2
Find the center of the box-shaped portion. Draw a line with the pencil from the top left to the bottom right and the top right to the bottom left. The intersection of these two lines is the center of the box-shaped portion.
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3
Measure from the center of the box-shaped portion along the handle to approximately the center. The actual distance doesn't matter but make a note of the distance.
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4
Calculate the force you are applying to the end of the wrench. This is the weight in pounds, multiplied by the distance in feet. For example, if you put a 10-pound weight 24 inches along the handle, then you are applying 20 foot-pounds of torque to the wrench.
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5
Set the wrench to the force you calculated in the previous step. Hang the weight at the exact distance you calculated. If the wrench clicks, move the weight toward the vice. If it does not click, move the weight toward the end of the handle.
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6
Find the point farthest from the end of the handle at which the weight causes the wrench to click and measure the distance. Use this distance to calculate the force applied to the wrench the same way as before. If the wrench is now 18 inches from the handle and still 10 pounds, then you are applying 15 foot-pounds of torque. Since the wrench is still set at 20 foot-pounds of torque, the difference allows you to calculate the inaccuracy of the wrench and factor it in next time you use it.
Tips and warnings
- Be as accurate as you can with the measurement. The more accurate the measurement, the more accurate the wrench.
