How I check my torque wrench

[joshuabardwell]

Also, most torque wrenches are accurate in the middle of their range. They fall off the bell curve as you go ove/under the middle of thier range... If you meaure 20ftlbs on a 150ftlb torque wrench, it will not be in it's more accurate range.

A good question is, just how accurate do you really need the wrench to be? I have read that a typical wrench is accurate to +/- 4% of its read value, for a total precision of about 8%. That's pretty substantial if you're thinking of it as a scientific instrument, but do you really need your lug nuts to be tightened down more precisely than that?

[RobertN]

For lug nuts no. But after working in high-tech labs for years, I'm so used to critical tolerances

A good question is, just how accurate do you really need the wrench to be? I have read that a typical wrench is accurate to +/- 4% of its read value, for a total precision of about 8%. That's pretty substantial if you're thinking of it as a scientific instrument, but do you really need your lug nuts to be tightened down more precisely than that?

[dodge man]

I check mine by letting the tire shop put on my lug nuts. If it takes about 300 ft lbs to take them off, my torque wrench is perfect.

[lostcause]

I check mine by letting the tire shop put on my lug nuts. If it takes about 300 ft lbs to take them off, my torque wrench is perfect.

i don't think i'd ever resort to an adjustable torque wrench for installing lug nuts. it's torque sticks and an impact for me. good job to the original poster though, for coming up with a homemade method to calibrate.

[joshuabardwell]

For lug nuts no. But after working in high-tech labs for years, I'm so used to critical tolerances

The older I get, the more I appreciate tolerance ranges. If something has to be accurate to within 1/10th of a degree, or 2 ft-lbs, then I will take great pleasure in devising a mechanism to accomplish that. But the rest of the time, I get it in the ballpark and get on to something else. Git-R-Done!

[Toyboy]

I find this thread interesting because I picked up an OTC 10-250# torque wrench at flea mkt. It's in really nice shape and I was wondering just how to check calibration. Now I have several options on doing that. If it's within 5% I'll be a happy camper.

[scrappy isb67]

This was discusses not too long ago.

There are palces that will calibrate torque qrenches. Sometimes even the Snap-On truck. Otherwise if you google/search in your local area, often there are calibration houses that have the strain gauges to do the measurements.

Also, most torque wrenches are accurate in the middle of their range. They fall off the bell curve as you go ove/under the middle of thier range... If you meaure 20ftlbs on a 150ftlb torque wrench, it will not be in it's more accurate range.

at work we were taught to not use a torque wrench if the value needed is in the top or bottom 10% of its range.

A good question is, just how accurate do you really need the wrench to be? I have read that a typical wrench is accurate to +/- 4% of its read value, for a total precision of about 8%. That's pretty substantial if you're thinking of it as a scientific instrument, but do you really need your lug nuts to be tightened down more precisely than that?

I check mine by letting the tire shop put on my lug nuts. If it takes about 300 ft lbs to take them off, my torque wrench is perfect.

I was also taught to NEVER use a torque wrench to break torque on a fastener! it is only for tightening! what I was told is that breaking torque on a fastener with a torque wrench screws up the calibration of the torque wrench.

[EE_Bota]

[QUOTE=scrappy isb67;2906178]at work we were taught to not use a torque wrench if the value needed is in the top or bottom 10% of its range.

I think what you were taught is fine.

The internals are fairly robust, but the spring should be stored slack, and care should be used with the setting process.

How does a torque wrench work?

[joshuabardwell]

I was also taught to NEVER use a torque wrench to break torque on a fastener! it is only for tightening! what I was told is that breaking torque on a fastener with a torque wrench screws up the calibration of the torque wrench.

My understanding is that is because the nuts can sieze up and the torque to remove them can exceed the wrench's range, even if they were put on to spec.

[dodge man]

I check mine by letting the tire shop put on my lug nuts. If it takes about 300 ft lbs to take them off, my torque wrench is perfect.

I forgot to hit the "sarcasm button" when I posted this. I'm not sure how high my torque wrench goes, but not anywhere near 300 ft-lbs.

Years ago I checked my torque wrench just by comparing it to a lug nut tightened by another torque wrench. They seemed close.