Calibrating a Torque Wrench in Your Garage

[Antichrist]

Anyone tried this?
http://www.dieseldoctor.com/messageboard/data/229.html
Almost seems too simple to be true.
Obviously you'd want an accurate scale to figure your weights.

 

[ntsqd]

Anyone tried this?
http://www.dieseldoctor.com/messageboard/data/229.html
Almost seems too simple to be true.
Obviously you'd want an accurate scale to figure your weights.

When we built the dynometer at my old employer we used exactly that method to calibrate it's hydraulic load cell and "pressure" gauge. The key things are that the length measurement be very exact and that the weight measurement(s) also be very exact. I would be inclined to check the torque wrench with several different weights as any error in one may not be linear. If you only test one point you can only assume linearity w/o knowing that it truly is.

 

[SunTzuNephew]

When we built the dynometer at my old employer we used exactly that method to calibrate it's hydraulic load cell and "pressure" gauge. The key things are that the length measurement be very exact and that the weight measurement(s) also be very exact. I would be inclined to check the torque wrench with several different weights as any error in one may not be linear. If you only test one point you can only assume linearity w/o knowing that it truly is.

Thats right. IIRC, when torque wrenches are calibrated in metrology labs for certification, they are calibrated across their range for that very reason. I have an old Proto wrench with long-form calibration certification (long since out of date) traceable to NIST standards and thats how they did it. Of course the certification costs more than most wrenches do to buy.

 

[Antichrist]

Yeah, I have a postal scale that I think will get me the weight within a few oz. It only reads to 5lbs, but figure if I want to torque a fastener accurately to 20lb, then I can find 5 4lb items to hang from it, like in a paint tin, and figure out what the setting needs to be for the 20lb value.

The reason I'm asking is because I'm doing a head job and the head bolts are 20lb/ft then 90 degrees, and 90 degrees again, so I want the torque value spot on.

 

[Wyowanderer]

TR calibration

I used to work at an engine rebuilder, and the Q/R guy would calibrate our torque wrenches as part of our job. He still does, and I haven't worked there for years. I suggest y'all develop a friendship with your local ER or macine shop, and get them to do it.
Nice post, though.

 

[david despain]

http://ttlcal.com/

this is the place I use. i have pressure gauges, torque wrenches, volt meters, inclinometers, strain gauges, push pull gauges, angle gauges etc. done there. its fast easy, they have great customer service. it's very easy to just send them the tools and get them back in a few days all nice and shiny with a cal sticker on them.
it's only $31 to cert a 1/4" dr. torque wrench. it's only ten dollars more for a half inch drive wrench. of course if you really dont want to pay any money you can always figure out a way to do it yourself, but my time is worth money and this way you get NIST traceability.

http://www.ttlcal.com/index.php?option=com_wrapper&view=wrapper&Itemid=153
here are some torque wrenches they sell. these are the same as snap-on torque wrenches. this company cdi makes them for snap-on or maybe snap-on now owns cdi...i dont know but they are definitly the same.