Maths help please!

[Caro]

Had I known I was going to take up jewellery making I might have paid more attention to certain parts of my maths lessons!


Is there a formula for working out how much longer a piece of wire will get when flattened? I have some 4 mm round copper which I want to flatten to make 500 mm of 0.7 mm thick "ribbon".

This is a prototype for a recreation of a Bronze Age twisted gold necklace that I saw in a museum the other day but for obvious reasons I want to experiment in cheap metal first.

And apologies if this is a silly question but does the relationship hold true for all metals or is the calculation going to be different?

[Dennis]

The first question in return Caroline, will be flattened how? Presumably in a rolling mill, and if you carefully feed it through slowly and square on,
then if you start with L mm of 4.00 diameter wire and reduce it to 0.70mm in thickness you will end up with 40/7xL=about 5.7 times as long.

That's what I make it, but someone will correct me if I'm wrong. There will be some variables not accounted for, so ultimately you must test it using copper.
The result will be similar for different metals, but some need more frequent annealing. Dennis.

[Dennis]

I haven not mentioned stretching. If you can achieve your aims by rolling only, then the width will remain roughly the same.
More likely you will have to intercept any tendency to curve (right or left) by stretching.

You might do this by annealing, clamping one end in a fixed vice, and pulling on the other with handimans serrated pliers.
This will lead to damage at both ends, to be snipped off and discarded, and to a narrowing of he band.
There is no formula to estimate for this. Dennis.

[Caro]

Fabulous Dennis - thank you. Yes it will be by rolling mill and I'll be roping in my assistant to help keep it straight!