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## Re: Torque wrench tester

 To: "List Spitfires" Re: Torque wrench tester "Graham Stretch" Mon, 7 Feb 2000 21:16:39 -0000
 ```Hi Carter If I send you my TW could you do the 3D graph with deflection compensation etc. What was that? you'd like me to leave in short jerky movements? Graham ----- Original Message ----- From: Carter Shore To: Oliver, Chris MAJ ; Sent: Monday, February 07, 2000 3:01 PM Subject: Re: Torque wrench tester > > Try this: > 1) On your Torque Wrench, measure and record exact > distance from center of socket adaptor to handle > pivot, or center of handle if no pivot. > 2) Clamp a large bolt horizontally into a bench vise. > 3) Use socket on TW to fit bolt head. > 4) Adjust bolt position in vise so that arm of TW is > horizontal. Use a level if you are AR. > 5) Attach coat hanger wire to TW handle, use duct tape > as required. Attach in exact center of handle if no > pivot. > 6) Using known weights (should be easier to find a > precision scale than a precision torque meter), attach > weights to coat hangar, record TW readings. If you are > AR, also weigh the coat hangar and duct tape and TW > itself, plus calculate the centroid of TW. > > Calculate the applied torque on the wrench by taking > the product of the distance from step 1, and values of > the weight(s) from step 6. (convert from in-lb to > ft-lb as required) > > If you are AR, put the values into a spreadsheet, then > print a color graph of the calibration curve, and post > it on the wall of your garage. > > If you are *truly* AR, perform the trials above at > different temperatures, then you can print a 3-D graph > that is temperature compensated. Can also measure any > deflection in TW arm, then do vector math to > campensate. > > FYI, unless you are torqueing brand new threads or > aerospace fastener\$ under absolutely ideal conditions, > any values must be considered very approximate, (i.e. > +- 20%), as the variations in friction from the > threads, and mating surface under the bolt/nut are the > dominant influence on the TW readings obtained, > whereas the actual desired result is the clamping > force that is generated. That's why some fasteners are > spec'ed by measuring the stretch in length rather than > applied torque. > > So a 5% variance in TW is probably worth ignoring. > ( 5% of 85 ft-lb = 4.25 ft-lb) > YMMV > > Carter Shore > > --- "Oliver, Chris MAJ" > wrote: > > > > I have been kicking this around off line, and though > > maybe some one out > > there might have a good solution. How does the home > > mechanic test his > > torque wrench to ensure it is with in standard? I > > know that if you use it > > alot, and do a lot of mechanical work you develop a > > feel for torque. But > > what about if you don't have that "feel"? It was > > suggested that the local > > Technical College might be of help, and if your > > company has a facility and > > lets you use it you are good to go. I was looking > > for the home shop > > solution. Maybe it does not exist, but I would like > > to hear your ideas. > > thanks Chris > > > > > > > Do You Yahoo!? > ```
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