Torque wrench accuracy

If you find your local Snap-on-Tools dealer, he can send it in for service and have it re-calibrated. It does not matter which brand you own. I cannot remember how much it costs, but it was fairly reasonable.

You could also borrow a wrench from auto zone and compare it to yours. Not as accurate, but still ok...

This might also let you verify yours. Find a short section of 3/8" inside square tubing. Cut ashort length. Attach one end to your torque wrench and the other to a borrowed one. See how they compare at various settings.

Beware...your Snap on Guy will have wrenches to die for! Take lots of money...The TQFR 100 is my favorite!

i just had my snap-on recalibrated...$60

At a school I went to there were torque wrench testers mounted on the wall. Basically what they are is a pendulum with a weight on the far end and a socket for the square drive with some numbers marked where the end of the pendulum points to. So the basic idea is that normally the pendulum hangs vertically but the harder you torque on it, the more horizontal it becomes and the higher the weight is lifted, with the pointer pointing to higher numbers.

Since gravity rarely changes, these things are the gold standard and so recalibration of micrometer torque wrenches was not necessary. Just twist the handle so it clicks on the tester at whatever torque you are after, never mind what number shows up on the handle.

With some ingenuity and math anyone ought to be able to make one of these things.

Do you guys know how we all have some claim to fame? Well, here is mine. I sold torque wrenches to Morton Thikol. These were the folks that made rocket engines for the space shuttle. Remember the bad "o" rings that caused it to blow up? My torque wrenches were used to tighten this fitting.

I was very glad my wrenches were in spec....

Most calibration companies (look in the phone book) will calibrate torque wrenches to a NIST (or whatever system is used in Canada) traceable standard. I would look at the cost of the torque wrench vs. the cost of calibration. No use spending $50 to calibrate a $20 torque wrench.

Keep in mind that torque wrench accuracy is based on a percentage of the actual torqu value. As the torque value increases so does the amount of inaccuracy.