Torque wrench Check

[popawheelie]

I want to check my torque wrench to see if it is accurate.
A friend told me that if I clamp the square end of the wrench
in a vice sticking out level and hang 30 lbs. on the arm a foot
out from the center of the square end the torque wrench should
read 30 foot lbs. torque. Is this right?
If it is my torque wrench is waaayyy off!

[Guest]

Buy one that comes with a calibration certificate

[PNuT]

surely thats only valid when its new?

[Guest]

I did a search and found this site.
www.dieseldoctor.com/messageboard/data/229.html
You can calibrate you torque wrench yourself

I didn't bother though. I went to a local auto mech.
and borrowed his.

Tryed to take my craftsman torque wrench back
because it was so far off and they said measurement
tools have a 90 day waranty. What a piece of junk.

[Guest]

Recalibration should be performed at regular intervals using equipment that itself can be traced back to nation and international measurement standards - have you calibrated the weight you're using to test the torque wrench?

The test interval depends on how heavilly used the kit is. In our lab at work it varies between 3 months to 3 years (electrical and mechanical kit).

[popawheelie]

I'm just a guy in his home shop trying to calibrate his cheap whench.
There is a way you can do it. Gotta go.

[nicrump]

Your friend is right but didn’t give all the detail. Foot lbs is pounds in 1' leverage. Hang the weight at 1' from the center of the square drive.

If the handle of you wrench were 2' long then 30 lb at 2' would be 15 lb at 1'

[popawheelie]

Foot pound torque means how many pounds it takes to turn something a foot from the center of the pivot point.
I guess a lot of people don't know that. I didn't know it.
Not rocket science.
I'm not sure what nm stands for but it's the same principal.

[nicrump]

thats a newton metre, .737 foot lbs

i think

[bladteth]

nicrump wrote:

> If the handle of you wrench were 2' long then 30 lb at 2' would be 15 lb at 1'

Other way around. 30 lbs at 2' would be 60 lbs at 1', because:

M = F * r

where:

M - moment (torque)
F - force
r - force arm (distance)

In imperial system moment is given in ft-lb (foot pounds), in metric system we use Nm (newton meters).

[nicrump]

I stand corrected

[Karma]

Boy, am I torqued!!

Not really but it is a nice play on words. Hey guy's, I recently bought a Craftsman inch/pound click type torque wrench. Today I brought it to work to test its accuracy. For comparison, we used a Snap-On inch/pound torque wrench which is calibrated every 6 months. The Craftsman came in within 5% of the Snap-On from 25 inch/pounds to 240 inch/pounds. I was very impressed especially since it costs $69.00. The Snap-On costs several hundred. The Craftsman is definitely not junk. It's a good buy.

I also have a Craftsman 25-150 foot/pound torque wrench and it has been very good. I use it a lot and I would buy another. In fact, I have; the inch/pound one.