I just read your Orchid posting and thought I'd pitch in. When you're
using a rolling mill, you need to remember to continually rotate your
workpiece, either clockwise or counterclockwise, such that no facet
of the compression groove lands on the same side of the ingot
consecutive times. For example, let's say you're using a set of
square grooves to reduce an ingot's diameter... first, run the ingot
through under slight pressure, and make note of which sides face up.
As soon as the ingot comes out of the rollers, take a permanent
marker and color the top left side of the ingot. Next, rotate the
ingot 25%, so that the just-colored side is now at top right, and run
it through again. When it comes out, rotate it again so the darkened
side faces bottom right (etc., etc.), until you've reduced the size
by about 20-30%; when you have, stop and anneal the piece completely,
then resume your rolling once it's cooled and been pickled and
neutralized. By following these steps, you'll minimize both the
elongation of the cross section and the likelihood of cracking, as a
result of over stressing the material.
All the best,
Douglas Turet, G.J.
Lapidary Artist & Designer
P.O. Box 242
Avon, MA 02322-0242
Tel. (508) 586-5690