Looking at the documentation from most of the quality manufacturers of
torque wrenchs (Proto, Snap-on, Norbar, etc..) I see that I can
increase the "range" of a torque wrench by putting an "in-line"
extension on the *drive* end(not the handle end. By scaling the
reading/click setting accoring to a formula which accounts for the
length of the extension, one can apply a torque that is greater than
the wrench would do if there was no extension. (Just so I'm clear,
this is not the typical sort of extension that goes perpendicular to
the wrench, but is instead in line with the axis of the wrench.)

Now - I've searched far and wide and cannot find anyone who actually
makes or sells a simple extension that I can buy. I'm looking for one
that has a 1/2" square female socket on one end (where the drive end
of the torque wrench fits) with a 1/2" male square drive on the other
end. I've seen ones where the drive ends are open-ended spanners, box
ends, etc, but can't find a simple square-square adapter.

Here'a a link to a guy who's built a homemade version:
http://www.specialpatrolgroup.co.uk/...ue/torque.html

Of course, I could build one or have one built, but this seems so
obvious that somebody's got to be making such a thing. Lengths from
6" to 24"(+) would be OK for my needs.

Anybody have a source for such a thing?

-Dave