On Mar 25, 7:20*am, "Leon" wrote:

I have Jet, Bessey, and Cabinet Master parallel clamps. *None of them are
parallel at some stage of tightening and or depending on the opening on the
clamps. *Simply put, the bar will bend and that prevents the consistant
possibility of a perfectly parallel set of jaw faces. *

Mine aren't perfect, but they are close enough. I have a million
clamps, and to fight off the fact that they all twist a bit
(Besseys.... not much, though) I use a lot of clamps and a little
pressure.

BUT these type clamps
tend to work about as good as you could expect.

I think so. Most of the time when you see twisting or wracking it can
be minimized by reorienting the victims in the clamps.

However, when teaching others the art of the glue up, almost without
fail the most likely culprit in their glue up failure is placing the
clamps and material on an uneven surface to glue up. And uneven table
top, gluing on saw horses, etc., bring a whole different dimension non
parallel clamps.

When I glue something up in the field that requires this kind of
clamping, I actually level my "table" on the sawhorses by carefully
leveling the material I am using for a top.

This cuts out most of the problems.

Robert