Calibrate Torque Wrench

[ALP]

 Does anybody have a recommendation for a good and reputable shop to calibrate a torque wrench?   I suppose "reasonably priced" should also be a criteria.  Thanks much.

Andy in Hawaii

1971 280SL

[Raymond]

How do you know yours is out of calibration?  Autozone and Advanced loans tools, you could borrow one from three different shops and check them all against yours on the wheel lug nuts.  If they all click at the same place, you'd have an idea of how close they were in the 80 lb. range.  You could find torque values on lawnmowers for lower ranges.  (just thinking of bolts that are easy to reach.) 

[Shvegel]

Your local Snap-on tools dealer should be able to have it done for you but they might have an issue if it is not a Snap-on torque wrench. The calibration machines are not Snap-on specific so it's worth a try.

I really wouldn't recommend using the lug nut method of calibration. There are too many variables with regard to breakaway torque and friction to really be even close to accurate.

I have a pair of 1/2" drive sockets welded end to end in my toolbox that I used to use. I would send my dial type wrench(torque-o-meter) out the calibrate the rest against the dial unit. I would snap the dial wrench and a click type in either end of the adapter and set the click type wrench to mid range and pull the wrenches against each other and see where the click type wrench was in relation to the dial gauge.  We would do the entire shop in about 10 minutes.  Most good quality wrenches stay pretty accurate.

[merrill]

you should find calibration shops in the yellow pages / internet. 

I have a torque wrench tester (link below) I use to check my wrenches

http://www.denlorstools.com/home/dt1/page_8822_319/precision_instruments_pretc3f175f_torque_wrench_te.html

There are other calibration tools out there if you want to buy.  all the major tool suppliers have them as well as amazon.com

[pj]

Hello Gentleman,
I am a newbie when it comes to lovely classic cars, but I teach physics so I know what torque is. Other than comparing it to a different torque wrench, how would you calibrate it? How carefully does it need to be calibrated? Is 10% good enough? Why or why not? (Sorry. . . I just realized that sounds like an exam question 

Are you trying to calibrate the torque wrench against some kind of standard?
--Peter

[Shvegel]

Peter,
Torque wrenches are calibrated on machines designed for that purpose. Depending on the level of accuracy required you can get paperwork tracing the calibrating machine back to known standards. For our cars 10 percent is probably about the outside limit as long as it's a consistent 10 percent. for things like head gasket sealing etc I find surface conditions(flat and smooth) are much more important than an extremely accurate torque wrench.

How accurate the calibrators are depends upon the diligence of the operator.

http://www.norbar.com/products.aspx

I like the part about having the calibration weights calibrated for the gravity constant of the lab.

[66andBlue]

Back to Andy's original question.
This will depend on the brand of your wrench. If it is a Snap-on or similar upper level brand then the company will do it for a fee.  I believe that Snap-on charged about $40 for a calibration - w/o repair - and $80 with repair a couple of years back. Then there are companies specializing in these kind of jobs, for example: http://www.calibrationspecialty.com/
If it is a Harbor Freight wrench then it may be cheaper buying a new one from them. 
But the cheapest solution is to compare it to an older beam-type wrench (+/- 4% accuracy) since these rarely go out of calibration.

[ALP]

Thanks to everyone for answering.  I should have mentioned it is a ProGrade KD Tools 1/2 click wrench that is worth the money to calibrate.  Cost about $250.00 new.  I know it is overkill for non-aerospace apps but I love tools.  I would not be worried about the calibration but it has been dropped a few times and I am about to venture into the top end of my engine.  So while I realize that consistency of the torque is probably more important than absolute values, I figure that it is worth a couple of dollars to try to aspire to both accuracy and consistency.  Again, thanks much.  These forums are awesome.

Andy