Rolling Mill Question

[Briadha]

I have just received a rolling mill and am wondering what is the best way to flatten out the silver after it has
been through the mill, as at the moment the silver i am using is coming out quite curved and I'm warping the
silver when i use a rawhide hammer to straighten it. Any suggestions would be appreciated. Briadha

[Dennis]

Hi Briadha,

The first thing is to make sure the metal is annealed before you start. When you do this it is best to protect it from firescale by first warming and painting with a flux.

Next don’t aim to have the rollers very tight. The metal should go through quite easily and needs to be flipped over at every pass to reduce curling up. If in spite of this it begins to curve, turn it by 90 degrees, open the gap a little and roll the bulge through, closing the mill by stages until the sheet is flat again.
If the metal gets at all springy re-anneal. Let us know how you get on, Dennis.

[Briadha]

Thanks Dennis - It seems so commonsensical the way that you have put it. Many Thanks. Briadha

[andrew_berry]

Hi Briadha

If the metal is coming out curved then it means that the rollers are not parallel. If they were then the piece would roll perfectly even.

What make are the rolling mills?

Ours are now 25 years old and every so often we remove the handle and realign them.

Andrew

[Joe]

There are two directions of curve reflecting the two different responses.

Dennis is talking about curving in the up & down direction (which is probably what you're experiencing) and his advice is sterling as usual!

Andrew is talking about curving in the left & right direction and is, as ever, right to say that the gap between the rollers needs adjusting for that, so that both sides are evenly spaced.

The first rolling mill I was ever taught to use was 12 feet wide and had rollers over a foot in diameter and the metal (steel) had to be orange-hot when inserted. It took a good bit more than a raw-hide hammer to flatten that out if the adjustment was poor! Yet it's good that the scaled-down knowledge is applicable.

[Briadha]

Hi Andrew, I don't know what make these are, I bought them from ebay. Believe me it wasn't much of a saving! I'll try to find out if it's possible to realign the rollers. Thanks, Briadha ( They actually seem pretty well made
however).

[Briadha]

Hi Joe, My curving is in the up and down direction. I think that I may have had the rollers too tight possibly.
I haven't really had much of an education in using a roller mill, so your help is appreciated. Many Thanks,
Briadha

[Joe]

Aligning the rollers is both easy and difficult!

It really just amounts to getting both sides the same distance apart. If you remove the central handle ( the one that makes it tighter or looser) then you have two big cogs. All you have to do is twist those cogs so that the rollers are parallel then put the handle back on.

However, it is really hard to judge when the rollers are even! I tend to tighten both sides down as hard as I can by hand, then run a bit of copper wire through and check that it runs true. If it curves off to the left, that means the gap at the left is too large and the cog on that side needs to be tighter.

Even the most expensive and industrial of rollers need to be adjusted, but obviously the cheaper ones may need more frequent setting-up.

But Dennis has probably guessed your problem correctly, so don't fiddle with the gap until you can see that it is poor - just follow his advice about annealing and rolling in all directions.

[Dennis]

Thank you Joe and Andrew, for clearing that up. I just wanted to add two more things:


1. Most mills have powerful springs and they will go on doing their job, even at the second pass, so don’t be too hasty in turning your top screw down. Also don’t turn your handle too fast, because the slower, within reason, the more even the effect.

2. If your strip of metal gets longer than the flat part of your mill is wide, you will not be able to turn it sideways to correct a wave. But, provided you can accept a light texture, it is still possible to get a good result.
Anneal and correct it as much as possible with your fingers first. Then wrap it in an offcut of net curtain material, going over the top, right round the front and back underneath. When you now put it through the mill, not too tightly, the metal will come out flat again, but textured top and bottom.

Curtain material can be bought in quite small samples and is not very expensive. What is more you can make several passes using new material each time to get delicate interference patterns resembling silk.

Dennis.

[Goldsmith]

Briadha,
I am not sure how well your workshop is equipped but here is a trade method for flattening silver sheet. Assuming that the silver sheet is tree inches square you need a couple of steel G cramps, two sheets of 4inches x 4 inches flat steel, I buy steel called ground flat stock which I buy in 300mm. x 100mm. x 3mm.thick sheets, First you anneal the warped silver sheet and let cool, then you clamp the silver sheet firmly between the two steel sheets using the steel G clamps, then on a forge you heat the whole lot with a large torch, I use my Sievert and place the clamped steels on a large firebrick and heat the steel until it is a dull red colour, then Ileave it to cool naturally and when cool release the clamps and the silver sheet will be perfectly flat and unmarked. This method works fine with any size of warped sheet, even for small pieces about two inches square just using one G clamp and two pieces of flat steel. The biggest advantage of using this method is that the silver or gold sheet is made perfectly flat and totally unmarked. As long as the steel sheet you use is larger than the sheet you need to flatten. I have seen silversmiths flattening large silver trays this way and using as many as a dozen G clamps around the steel sheets.
James