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<< Lancair Builders' Mail List >>
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Since most builders aren't certified repair stations, they don't have to
have their torque wrenches certified. I have some cheap Chinese torque
wrenches and they seem to be right on. I do have a ¼" Snap-On, I bought
used, and it was off when I bought it and I had to adjust it.
There are two (maybe an infinite number of ways) ways to check a torque
wrench (for non certified operations).
1 Take a torque wrench you are sure is right, clamp the handle it in a
padded vice and use a female coupler (or a short bolt with a nut and two
sockets) to hook it to the other wrench. Check them against each other at
25, 50 &75 % of their. Many wrenches are not accurate at the bottom or top
of their ranges
2 measure the distance between the center of the square drive and the center
of the handle (The place where your hand grabs it) to the nearest 0.1" (for
list members to the nearest ).001"- This cuts the arguments, but you can't
grasp the wrench that accurately). Set the wrench for 25% of it's range.
Clamp the square drive in a vice and position the handle horizontal (use
your level) with the direction of pull vertical. Hang a bucket at the
center of the grasping area and put junk (list members should use gold
coins) in the bucket 'till the wrench clicks (ok if you have a pointer 'till
the pointer reaches the desired value). Take the last item out of the bucket
and lift the wrench handle to reset it. Add lighter items till the wrench
reaches the right value. Weigh the loaded bucket in lbs. and 1/100 of lbs.
( 1oz = 0.0625 lb) . Multiply the measurement obtained above by the weight
of the bucket. This gives you inch/lbs. If you want foot/lbs. divide by 12.
Do the same for 50% and 75% values of the wrench range.
Small errors shouldn't hurt - note the min -max range of the size bolt you
are torquing. Most wrenches have a spring detent that can be adjusted. You
can think of the errors something like the errors on your compass card.
Bill N7WB
> [Interesting tidbit, John... I'm wondering where you'd take or send their
> wrenches for calibration? I'm of the impression that using an
uncalibrated
> torque wrench isn't much better than not using one at all. Just curious.
>
> <Marv> ]
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LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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