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[oletrucks] torque wrench accuracy

To: oletrucks@autox.team.net
Subject: [oletrucks] torque wrench accuracy
From: "Durwood B. Darbin" <dhckdkcsk@hotmail.com>
Date: Tue, 30 Jan 2001 11:10:07
My friends on the list,

It is 0345 and I am again shirking my work along with my no load work mates. 
  At these times I remember stuff that bugs me and I thought that I would 
share one thought with you all since I had just read about converting foot 
pounds to inch pounds on torque wrenches.

I was at my local garage the other day when I noticed a mechanic using a 
torque wrench without exercising it first.  He didn't know that torque 
wrenches need to be exercised.  Not many people know this but it is true.

I was a (pick one) []Calibrator, []Precision Measureing Equipment Specialist 
(PME)(PMEL), []Test Equipment dude, []Prima Donna, []Bone Head, when I was 
in the Marines for 21 years and nine months.  I calibrated all kinds of 
stuff that was peculiar and non peculiar to aircraft.  Torque wrenches were 
in the mix.  It was required that we 'exercise' the torque wrenches at least 
three times before proceeding with calibration.  By 'exercising' I mean 
setting the wrench to a high value and turning it until it exceeded the 
dialed in value and the head would 'give' indicating that the value had been 
reached.  The wrench would be off in excess of 10% on the first pull and 5% 
on the second and 1% on the third.  This applies to all torque wrenches, 
dial up values and fixed dials.  I have verified these error values by 
putting the wrenches on a standard and checking the results.

So please help me spread the word about torque wrenches.  They must be 
exercised three times before use to be accurate if they have been sitting 
idle for more than one hour.  Also the wrenches are most accurate at the 
center of their range so you shouldn't use foot pound wrenches for inch 
pound applications or vice versa.

For the REAL time call the National Institute of Standards and Technology 
(NIST) 303-499-7111.

Maybe I'll go to lunch now.

Durwood
51 Chevy 1/2 ton Deluxe 5 window

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