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Old September 16th 06, 08:48 AM posted to rec.crafts.jewelry
lemel_man
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Posts: 22
Default rolling mill questions

ted frater wrote:
...snip...
This one is something I can help you with.
Putting it simply, a rolling mill makes metal thinner IN the direction
of the rolling.
IE your 1.2mm wire will go down to the thinness you want BUT wont get
any wider!!.( ok I know there will be someone who will say it actually
does get wider by about 2/4 %)


I am surprised that this myth continues to be preached. Its simply not
true. I found that out when I wanted a 100mm 0.25mm x 1mm strip. I took
a 25mm length of 1mm square wire and rolled it down to 0.25mm. That
should do it, right? Wrong. I got a 50mm strip 2mm wide. That's when I
did the experiments. I did lots, plotted the results on a graph, applied
some curve fitting algorithms and came up with a pretty nasty equation.
I simplified it a bit and wrote a program that I've been using for a
number of years. Its not 100% accurate, but close enough to be extremely
useful. It also varies a little with the metal being rolled. I feed in
the width and thickness of the strip I need and it tells me the size of
the square or round wire I need.
For example, suppose I want a 3 by 0.2 strip 400mm long. It tells me I
need to start with 161.25mm of 1.22mm square wire, or 162.81mm of 1.37
diam round wire, and it will weigh 2.688gm in 9ct yellow gold.

You don't believe me? try it yourself. You must start with well annealed
wire and roll it aggressively, ie. minimise the number of passes and
anneal frequently. In the example I would set the roll to give 0.2mm
thickness in one pass, measure the result, adjust for the error (its
never too thin), and do the correction pass.
I can't believe I've got the only magic rolling mill in the world.


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

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