You need 4 things to check the accuracy of a torque wrench.
1.) A vise to clamp the square drive end of the torque wrench so that it is stable and isn't moving all over the place.
2.) A suitable weight that is within 2% of the weight marked on it.
3.) A ruler or tape measure.
4.) A coat hanger or wire strong enough to hold the weight.
Mount the square drive of the torque wrench in the vise and tighten it down securely. Measure from the center point of the square drive to the line in the middle of the torque wrench handle or handle pivot. Multiply the measured distance by the known value of the weight.
Example:
14 inches x 50 lbs = 700 inch pounds.
Divide by 12 to get foot pounds: 700/12 = 58.33 foot lbs.
If the torque wrench has a setting dial, set it to the value you just calculated. Attach the wire or coat hanger that has the weight to the pivot point, or line on the handle. Listen for the click or beep, or watch for the flash or the indication on the dial. It should match the calculated value within 2%.
That’s the simple part. Unfortunately I have no idea how to adjust anything but the bending beam torque wrenches, so you are on your own from this point on.
What brand is it? I believe you can just walk into a Sears and hand them your Craftsman wrench and they will get it calibrated for you. Not sure how much it costs.
jrichker's post makes perfect engineering sense, but I see a couple issues:
1. The weight of the wrench itself is ignored
2. It only measures the calibration of the wrench at one specific value. Torque wrenches need to be calibrated for accuracy all over their operating range.
What brand is it? I believe you can just walk into a Sears and hand them your Craftsman wrench and they will get it calibrated for you. Not sure how much it costs.
jrichker's post makes perfect engineering sense, but I see a couple issues:
1. The weight of the wrench itself is ignored
2. It only measures the calibration of the wrench at one specific value. Torque wrenches need to be calibrated for accuracy all over their operating range.
He's right. The beam style torque wrenches only require you to bend the pointer so that it reads zero when at rest. Other than that, they never go out of calibration.You could just buy a beam style torque wrench, tighten a bolt in something to a specific torque then use your click style to confirm and then return the beam style once your testing is complete. If the bolt moves a little (couple degrees) and clicks, then it should be fine. If it instantly clicks and doesnt move keep increasing the torque setting on the wrench till it moves a couple of degrees and clicks. If this increase in the setting is to far off for you, then you have your answer.
He's right. The beam style torque wrenches only require you to bend the pointer so that it reads zero when at rest. Other than that, they never go out of calibration.
That's the way the AF teaches. Of course they also want the torque wrenches calibrated every 3-6 months. The AF also teaches that you should never use a torque wrench at their lower and upper values due to calibration. I want to say the lower/upper 30% but I just can't remember. Most of the guidelines just aren't practical for home use though.That's Probably the best way to test it then. Is it true that you should never use a torque wrench to loosen a bolt. only to tighten?
That's Probably the best way to test it then. Is it true that you should never use a torque wrench to loosen a bolt. only to tighten?
... Is it true that you should never use a torque wrench to loosen a bolt. only to tighten?
Yup. That's because in real life, springs are not 100% linear.That's the way the AF teaches. Of course they also want the torque wrenches calibrated every 3-6 months. The AF also teaches that you should never use a torque wrench at their lower and upper values due to calibration. I want to say the lower/upper 30% but I just can't remember. Most of the guidelines just aren't practical for home use though.
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