"bob prohaska" wrote in message ...

Jim Wilkins wrote:

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It's really hard to tell without handling the pan, but perhaps the edges
of
the bottom have been stretched larger than the center. Making many narrow
bends sequentially can do that, since the metal stretches to accommodate
being bowed out. If the center was larger the edges would be stable and
the
bottom would bulge and be in/out bistable. Hammering around the center
against a solid steel block might stretch it enough to remove the twist,
though judging where and how much to hit is tricky, an acquired skill. An
auto-body planishing hammer with a smooth face is neater than a ball pein.


Are you saying the bottom of the pan needs to be stretched, as in given
more area, to relieve the stress? I can do that, though it won't be pretty.

I tried simply straightening the flanges I'd bent, and the twist promptly
vanished. But, of course, the pan was now too wide. So I cut the offending
flanges mostly off with a pair of snips. The twist returned. Looks like the
twist is intrinsic to the pan and was somehow restrained by the flanges.

It's really tempting to think that forming what remains of the top flange
will flatten the pan bottom, but I can't visualize what it'll take.
Is that what you mean by:

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My initial guess of what you did may have been wrong, I was thinking of a
narrow rolled edge at the top like on my pans instead of a wider flat
flange. If the side wall has bent into an arch because the upper edge
stretched you may not be able to fix it unless you shorten the edge by
crinkling it, perhaps with little twists with strong tapered nose pliers,
not fragile little electronics needle nose ones. It's informative to try
even if the result is trash. The causes of sheet metal distortion aren't
always obvious and it can be easy to fix but expensive to replace, like the
housings of lawn and garden equipment. I straighten the corrugated galvy
roofing on my wood sheds after fallen branches crumple it, by
rubber-hammering it over 1-1/2" water pipe on sawhorses.

This is the tool for more serious crimping, like joining stove pipe or
forming a custom round pan or cover.
https://www.amazon.com/Sheet-Metal-C...+Metal+Crimper

A steel plate held upright in the vise might help as a form to bent the
flange of the next pan down gradually and uniformly. Once you have the bend
half completed the vise (with padded jaws) can finish it, again a little at
a time across the full width.