Torque Wrench calibration

[crucifyd]

I have a Snap-On torque wrench that I've had for 35+ years and I know that it is out of calibration.
Calibration doesn't seem practical from a time or $$$ standpoint when you don't use the
wrench that often...

A couple methods I've used to try to get accurate torque are:

- for lug nuts in particular, before loosening, tighten w/the TW and adjust the setting
until it clicks and it just starts to turn the lug then use whatever setting the TW ends up at...

- put the TW drive into a vise, setting the handle parallel to the floor and hanging some old metal
free weights (90 lbs) I have on the handle, ajusting the setting until it clicks just as the weight is free
hanging. The first time I tried it, it seemed to work well. I did the same this weekend and it didn't click
until I had the dial @ 145-ish lbs but a couple hours later I hung the weights again came up with 75ish lbs....kinda blew my confidence in that method...
could the TW be changing that much / that short of a time frame?

All that to say, the question is, if you don't use a torque wrench often, how do you torque with
any accuracy w/out getting it calibrated every time?

 

[limp]

Last I looked, Snap on has a lifetime warranty.... Try hunting down a snap on truck and see what they say???? I ASS U ME they would send it back to get recalibrated for you for FREE......

 

[Noobz347]

It doesn't have to be calibrated every time. There is a maintenance interval.

Everything you wanted to know about calibrating a torque wrench:

https://www.snapon.com/display/901/WWW/Products/TorqueTools/CalibrationManual.PDF

Here is a blip about their calibration services:

Calibration Services

 

[85GTStangGuy]

Properly handled, stored and used, a torque wrench should be fairly accurate for a long time. That said, 3-1/2 decades is a long time.... that may be long enough for the spring inside to fatigue (assuming it's a mechanical, not a digital, wrench).

Don't know, but you may be able to use a digital torque adapter to roughly see the accuracy of your wrench.

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Last I looked, Snap on has a lifetime warranty.... Try hunting down a snap on truck and see what they say???? I ASS U ME they would send it back to get recalibrated for you for FREE......

That would surprise me.... that is, a recal for free. I would suspect their lifetime warranty is for failure (or a similar malfunction), not for recalibrating, unless it was required due to a covered component failure. Like @Noobz347 said, there is probably a recommended recal interval. At my place of employ, all our test instruments are on a 12 month recal interval. That being said, it's certainly worth a shot with the Snap-on salesman.

 

[AeroCoupe]

You can typically find local places to do this for around $75. I have mind done every five years or so as I don't use it that often and I take care of them.

 

[crucifyd]

oh man I feel stupid, when I did the hang the weights process I totally forgot about
doing the math formula for varince in TW length, so who knows what I ended up with

It doesn't have to be calibrated every time. There is a maintenance interval.

right... I didn't mean if you used it with short intervals between, I meant if it was
used infrequently enough that it might be out of calibration...

Properly handled, stored and used, a torque wrench should be fairly accurate for a long time. That said, 3-1/2 decades is a long time.... that may be long enough for the spring inside to fatigue (assuming it's a mechanical, not a digital, wrench).

Don't know, but you may be able to use a digital torque adapter to roughly see the accuracy of your wrench.

it is mechanical...
I thought of the adapter before but wondered if the same thing might occur with that...

 

[Bullitt347]

Most Snap-On trucks have a Torque Wrench checker.
It can tell you how far off, if at all, your torque wrench is.
It if reads 5 lbs low. just add 5 lbs to your wrench. Ect.
They do not charge to test your Torque Wrench, it take 15 seconds.