Beryl writes:

Joe Pfeiffer wrote:
It's hard for me to imagine this making a significant difference.

A chain wrench, strap wrench, oil filter wrench, pipe wrench,
vise-grips as in the picture, etc., are made to work well in one
direction.

Many of the wrenches you've described -- in fact all but vice-grips --
are indeed designed so that turning in the "right" direction makes them
grip substantially tighter. Not true of vice-grips, and really doesn't
look true of a nut in a clamp (in this case the clamp is the vice-grips,
of course).

? A situation where a split "stud" grabs the nut around it...
?
? Think of drum brake shoes. When forced outward, the leading edge of a
? shoe wedges tightly against the turning drum. A trailing edge forced
? outward isn't very effective.

That isn't how self-energizing brakes generate extra friction --
friction against the drum rotates the shoe assembly forward, and the
front shoe works to push the rear shoe harder against the lining.
Yes, it is the trailing shoe that applies the most force against the
brake drum.

Right -- but it isn't because the leading edge is wedged against the
drum.

I'm thinking of motorcycle front drum brakes, which evolved to
dual-leading shoe designs with two cams, lifting the leading edges of
both shoes.
And then, they had very little stopping power when rolling backward,
which didn't matter anyway. They worked significantly better in one
direction.

Not familiar with motorcycle brakes -- but with automotive brakes, the
brake cylinder pushes the top of both shoes, and the friction of the
front shoe against the drum ends up pushing the bottom of the rear
shoe. It also works substantially better forward than reverse, but
that's not because of any wedging.

In this case, I think the grip on the nut slipping or the stud snapping
will happen before the nut turns on the threads.

Agreed.

I snap the stud, absolutely.

--
It's time to try defying gravity