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" <oliverc@monroe.army.mil>
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
>
>
>
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