arren123

I just finished re-calibrating my 3/8" torque wrench. I was surprised to find out that it was about 2.5 lb-ft under. I just bought a 1/2" drive torque wrench and tested it and it was dead-on. Does anyone else re-calibrate their torque wrench themselves?

The way I did it was to use the cheaper 3/8" torque wrench (the one where the arm bend and a pointer shows the torque applied on a scale).
I set the click-type torque wrench to 20 ft-lbs. Next, I put a nut in between the two torque wrenches and apply torque to the cheaper wrench. I slowly apply torque to 20 ft-lbs. If set correctly, at 20 ft-lbs, the click-type torque wrench will click. Repeat the test at 30 ft-lbs. If everything checks out, I tighten the set nut and test it one more time.

Since, the click-type torque wrenches go out of spec, its a good idea to use the cheaper one as a base line.

I know people have said that these cheaper torque wrenches with the bending arm are way-off, but it doesn't seem so to me. Any comments?
I think this is a nice cheap way to re-calibrate your torque wrenches.


[Modified by arren123, 4:38 AM 1/20/2002]

EPGONZALEZ

actually th deflecting bar and click type are very simliar...they both usespring pressure as a way of measuring torque...the deflecting beam just never seam to wear out though...but it is also harder to get an accurate reading from the deflect. beam as well...especially over 20lbs..

chad

excellent question for a board like this where most of us do our own wrenching (not wenching!!)

siisgood00

id like to know too...

bussetech

I have a Craftsman wrench, and according to the booklet, I should take it to Sears, but the warranty doesn't cover recalibration

Its_real&its_spectacular

Time to fish out the Snap-On Catalog. They sell Torque Wrench testers. I seem to remember them being in the several thousand dollar range...

arren123

I think I'll stick to my method

bussetech
IMO, forget about bringing it to Sears. The three torque wrenches I have are Craftsman. I think the deflecting bar torque wrench only costs $17. You need to pop off the end cap from the handle. I used a small blade from my swiss army knife.



A socket won't fit over the nut in the handle unless you have some kind of thin-wall socket.



You can use a set of small needle nose pliers to turn it. If it won't turn, you can jam the pliers into the side of the nut and just turn the handle of the torque wrench just like when you are setting the desired torque. You can use an allen wrench to turn the inner bar to calibrate the torque setting. Lefty loosey (less torque) - Righty tighty (more torque). After its calibrated, make sure you tighten the nut nice and snug or else it won't follow the handle when you select a higher torque setting.

Jefe1230

Actually, the whole purpose of calibrating an instrument is to compare it to a known standard that is better than the instrument in question. In the calibration world we use a standard that is at least 4 times better than the accuracy of the item we are calibrating. Using one torque wrench, especially one that isn't as good as the one you are wondering about, only proves that the one you are calibrating is at least as bad as the one you are using for a reference. Granted, most torque wrenches are only accurate to +\- 4% of the indicated reading, i.e. a 5-150 in-lb click-type wrench set at 75 in-lbs can vary anywhere from 72-78 in-lbs. If the wrench is checked against another wrench on a nut set-up as described, and the dial wrench is accurate to +\- 2%, you actually have a variation of +\- 2% because the "standard" wrench (dial) is only 2x better than the one you are checking.
So do the right thing, if you are curious about your wrench, have it checked by a professional, especially if you drop it on a hard surface or it's an old wrench. By having your tools calibrated correctly, you could avoid potential litigation later by someone that knows about this stuff if there ever were to be an accident and the question of whether you torqued that nut correctly ever arises.
Just saying........

Jefe1230

Sorry Arren123, making adjustments to a wrench when you have no idea how close you are to the correct reading is just plain stupid. How do you know how accurate you are? You can't just go around making adjustments to things. The most accurate way is to find a place in your town that does calibration. Most machine shops either have or know a reputable calibration lab. If you're going to do it, do it right. Buying your own tester isn't a bad idea, but you have to learn the proper use of it. It usually needs to be in a clean environment. and it too needs to be calibrated once in a while.

nsxtasy

Are you really expecting an answer when replying to a topic that is eight and one half years old?