br wrote:
I doubt that "wobbles and bends" would be a big problem as the disks
will be hand-punched.

You may not have trouble because of "wobbles and bends" but you'll have plenty
of other problems. You better have a damn good punch for that, because if you
don't you are going to have a hell of a time punching circles out of .1 mm thick
sheet. That is not even sheet anymore, but almost foil. If you punch is not
made to a very tight tolerance, you will drag the sheet into the punch and you
will not get a clean cut. I have circle cutters, that have decent tolerances,
and I cannot cut anything very clean that is thinner than .3 mm. For larger
circles I make my own punches, that cut just fine. I leave them unhardened,
because it doesn't really matter for gold, if they are hard or not, and I do not
have to cut thousands of circles.

Am I correct in assuming that the "straightness" of
the ribbon depends on the parallelism of the two rollers? Concerning a
polished surface (only one side needs to be polished); would it be feasible
to use a long strip of highly polished spring steel, run through the mill at
the same time as the gold ribbon, to polish the surface?

That is the single best way to destroy your rolling mill in short order! (Well,
maybe not neutralizing your sheet well from acid after pickling is a better way)

If I'd see you do that in my shop, I'd kick you out the door faster than you can
say "Oh ****!" I have seen idiots doing stuff like that with bunched up steel
wire to create an "interesting" rolled pattern on sheet. They ended up with the
patterns in the gold and silver, as well as on the rolls!

Rolls of mills are usually only case hardened, which hardens only a very thin
outer layer of the rolls.

--
Abrasha
http://www.abrasha.com