[Spridgets] FW: Torque wrench extension

[Bill Masquelier]

At Boeing (where I WAS a tool design engineer before I retired this month) we
have and use a simple principle with torque wrench extensions.
If you put the extension on in-line with the handle (as is shown on the PDF)
you use the simple calculator.
An easier way is to put the extension on at 90 degrees, make sure that the
extension is no more than 1/2 the length of the wrench handle and no
correction is needed (I didn't believe it either until I made a test and had
Cal-cert prove it to me on their tester machines!).
For ease of calibration many if not most of the extended torquing is done this
way in the factory.
BillM

> Date: Fri, 5 Aug 2011 17:39:21 -0500
> From: bjshov8 at tx.rr.com
> To: spridgets at autox.team.net
> Subject: Re: [Spridgets] Torque wrench extension
>
> As an engineer I know more than a little about torque, bending and
> deflection, but I stayed out of this discussion the first time around.
>
> For a mechanical wrench of this type the amount of extension really
> doesn't affect the torque.  You can play with their calculator and it
> will show this as well.  For instance set the lefthand extension to 0
> inches, which is the normal case with a torque wrench, now change the
> length of the wrench to anything you want.  The torque applied to the
> fastener will still equal the torque indicated at the wrench, because
> that is exactly what it is measuring.  With different wrench lengths it
> will take less pull by the user to achieve that torque.  Now if you add
> an extension on the lefthand end of the wrench you will get a different
> answer because now you have the applied torque indicated by the wrench
> plus the force you are applying multiplied by the additional extension.
> I'm not aware that this type of extension is commonly available but if
> it is then their calculator would be very useful to you.  I could write
> the equations to get the same answer.
>
> Now if you are using a BEAM torque wrench, then it is slightly
> different.  The calibration of the beam is based on a predetermined
> bending moment condition in the beam.  If you put an extension on either
> end of that type of wrench then you would change the bending
> characteristics of the beam and get a different answer.
>
> I have experience with both types of wrench and a wrench that clicks is
> certainly easier to use, but a beam wrench that is not damaged and that
> is used correctly will never go out of calibration.
>
>
> > A short while ago there was a discussion over using an extension bar
> > with a torque wrench.  The below may help.
> >
> > http://www.belknaptools.com/downloads.asp
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