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Old September 16th 06, 04:58 AM posted to rec.crafts.jewelry
lemel_man
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Posts: 22
Default rolling mill questions

br wrote:


Indeed, my calculation of the diameter of wire
(1.2mm) needed was based solely on the cross-sectional surface area, and
didn't take into account the differences between lateral spreading and
elongation. Perhaps starting out with 0.5mm thick by 2 or 3mm wide would be
easier?

The wire gets longer and wider when you roll it. The textbooks usually
state that the width doesn't alter much, but I've found that it does.
According to my calculations, if you roll 1.65mm square wire down to
0.5mm thick it will spread to be about 3mm wide. The volume remains
constant of course.

I doubt that "wobbles and bends" would be a big problem as the disks
will be hand-punched. Am I correct in assuming that the "straightness" of
the ribbon depends on the parallelism of the two rollers?


If the rolls aren't parallel you will start to roll an arc and when you
try to correct it it will start to go wrong. If the rolls are truly
parallel _and_ you keep the straight wire at right angles to the rolls
you will produce a nice straight strip, but its harder to do than to say.

Letting the wire enter the rolls at other than right angles is the most
common cause of a curved strip. Allowing the wire to wander sideways
causes it to enter the rolls at less than 90 degrees, thus again
creating a wiggle.

I've found that holding the wire in some thick smooth faced pliers,
right up close to the rolls so that they actually rub (being thick there
is no chance of the rolls grabbing them), keeping them at right angles,
and squeezing them gently while rolling works pretty well for me.
Squeezing the wire with the pliers ensures that the rolls actually pull
the wire, thus tending to keep it straight.

Once you get a wobble on the strip its almost impossible to remove it.
If its not too severe you can sometimes rescue it by winding the strip
into a tight whirl, holding it together with binding wire, annealing it,
removing the binding wire and gently hammering the whirl flat.
Unfortunately its not a guaranteed cure 'cos the parts of the strip on
the outside of a curve will get hammered the most and will therefore be
a little thicker; when they get rolled they get spread a little more and
tend to be on the outside of the curve again. But sometimes it works.

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?


Most good rolls have nicely polished hardened rollers which impart a
pretty good surface ready for polishing. If you take care of them they
last a long time.


--
Regards, Gary Wooding
(To reply by email, change feet to foot in my address)

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