Don Schwartz wrote:
"One blade is quite straight, the other veers off like a fork in the
road. I measured the separation at the tips with a rule. The inside of
the bent shear (the meeting surface)  is convex, not concave."


Egg on my face. I should have read the whole thread before replying. Pass over
that spitoon.

But, now that I realize what the problem is:

I have a Stilletto 5/8" chisel with about 5" of blade, that was so badly bellied
or bent that it couldn't be flattened by stock removal. I put it in the
woodworking vise and squeezed it flat, left it a few hours. It sprang back when
the vise was opened. Put it in back in with the ends blocked one way and the
center blocked the other, using rolled-up paper towels to give a softer
transition, and closed the vise slowly to over-bend it, left it a few hours.
Same thing again, with more blocking, and again, maybe four or six times total.
Each time it improved a bit, and each time I was convinced that I was going to
snap it when I closed the vise. It finally got to the point where I could live
with it. Ground away what was left of the belly and it sharpened up real nice.


The key was putting on the pressure slowly and gently, spreading the pressure
out a bit, and letting the blade rest in the over-bent position a while before
taking the pressure off. I tried a sudden smack with a hammer and it basically
did nothing; I think I would have snapped the blade if I had whacked harder.

Tom Conroy, polishing.