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Old September 15th 06, 09:17 AM posted to rec.crafts.jewelry
lemel_man
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Posts: 22
Default rolling mill questions

Peter W.. Rowe, wrote:

...snip
Second, your understanding of what to start with, is wrong. Assuming you wish
to roll the wire in a continuous length so it passes straight through the mill,
if you want to end up with ten millimeters wide, you need to start with square
wire stock not a whole lot narrower than that. I'd run a few tests to find the
exact needed starting stock, but I'd hazard a rough guess you'll need to start
with stock roughly six millmeters square, maybe a bit more, from a square wire
rolling mill. Remember that rolling mills mostly elongate the stock. Only a
little of the spreading out is laterally, so the stock gets thinner and longer
as it goes through the mill, but only a little bit wider. If you started with a
round or square 1.2 millimeter wire and rolled it to a tenth of a millimeter,
you'd end up with somewhere in the area of 1.5 mm wide, not ten millimeters.



I'd say Peter was pretty much spot-on concerning the practicalities of
making your own 0.1mm strip and punching the discs. 0.1mm is pretty thin.
I tend to make quite a lot of strip in the work I do; usually 0.2mm up
to 1mm thick, and 1 to 5mm wide. The requirements are such that it is
completely impractical for me to stock all the strips I might need, so I
have to make my own. I have to anneal frequently and try to make the
minimum number of passes. Getting straight strip is a problem. I've
found that the first pass of the square wire is critical: if that
results in straight strip then its likely to continue that way. Best
results are obtained by making sure the wire enters the rolls at right
angles and by maintaining a slight tension on it. ie, forcing the mill
to pull the wire.
I often want to end up with strip of a particular thickness and width
and to that end ran a series of experiments to see how the width was
affected when rolling wire. The result was surprising: the width
increased rather more than I expected and more than Peter suggested.
Basically, when you roll a wire or strip the width increase depends on
the ratio of the previous width to thickness. The bigger the ratio the
smaller the increase, but its not linear. I worked out some sort of
correlation between the ratio and percentage increase and found I could
get pretty accurate results, especially for ratios smaller than about
10:1. Based on that work, I would say that 1.2mm square wire rolled down
to 0.1mm would end up close to 4mm wide.
For what its worth, my calculations suggest that 2.2mm square wire
rolled to 0.1mm would end up around 10mm wide. But as said above, the
accuracy at a ratio of 100:1 is not good. With more work it could
probably be improved, but in my case its just not worth it.

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

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