Today I got my second Craftsman brand torque wrench which like my first, I got through Ebay. I bought a 20-150 ft/lb 1/2 inch drive model to complement my first torque wrench, a 25-250 in/lb 1/2 inch drive model.
I'd been thinking I'd take them to Sears and they'd calibrate them for me so I would know that when I set a torque setting, it's accurate and I don't mistakenly overtighten or undertighten a fastener on my motorcycles as I service them.
Well, let me tell you, the Sears people I called on the phone were "uncertain" to put it kindly. The basic gist was: I think we send it somewhere and it'll come back someday, not sure what the cost will be though.
With that resounding assurance, I bagged that idea!
A few minutes of googling found me this LINK.
I followed the instructions, which even for a math-challenged guy like me were simple enough. I actually repeated the tests twice to verify my calculations and its good that I did because I missed a step on the second wrench!
I marked up the cases in which the wrenches are stored. So, now I know that for my inch/lbs wrench, I must multiply the desired torque setting by 1.25 and set that value on the wrench. For my foot/lbs wrench, I must multiply the desired torque setting by 1.13 and set that on the wrench to deliver an accurate torque on the fastener in question.
In other words, I've been undertightening my fasteners! This Maybe explains some slight seepage I saw on a couple of drain plugs after the last services I did on Brigitta. So, when's the last time you had your torque wrenches checked?
Update: 15SEP08: Turns out, where I am presently contracting for work, UAL's Flight Training Center, they've a Torque Wrench Testing device near the tool shop! I took my wrenches there today and checked both of them. They were reported, near as I can figure it out, as accurate! I am of course inclined to believe this certified testing device vice the crude methods I used to derive the mathematical values above. Oh well.
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