Rolling Mill Tips and Tricks
Q: I just got a small inexpensive rolling mill, and I’m starting to figure out how to use it. Can you suggest anything to do with it I haven’t thought of? I’ve already managed to roll out a tenth of an ounce of fine silver into a eighth-inch piece of wire six inches long in less than 90 minutes, annealing every few passes.
You should be able to do that much more quickly. Start by casting a rod-shaped ingot, if you didn’t already. If you need the means, take two pieces of mild steel which cah be aligned repeatedly in position, and drill a hole, perhaps 1/4 inch diameter, right down the plane where the two pieces meet, not going all the way through. The contact surfaces do not have to be perfect, in fact, some slop is good since it lets air escape. File or otherwise cut a chamfered top edge to a funnel shape so you can pour molten metal into it. In this fashion, with a bit of care, you can make a good wire ingot mold. Starting with a rod-shaped ingot, you should be able to reduce it to the desired size wire in a few minutes, including pouring the ingot. Assuming you’ve got a torch that will do it okay, the whole process shouldn’t take more than about ten minutes, not ninety.
With fine silver, you simply do not have to anneal very often. You can reduce the cross-sectional area by as much as 90 percent before needing to anneal, and this metal is so soft you’re not putting any strain on the mill by doing this. Annealing less frequently also will give you a stronger, finer, grain structure when you do finally anneal the wire. And you need not be too delicate in how much reduction you take with each pass. The initial passes with the round ingot can be gentler, but once it’s squared up and the rolls are fully closed on that first groove, from there on, you can reduce the wire the full amount for each successive groove in no more than 2 or 3 passes, and often, only one pass, depending on the type of metal.
Each pass through the grooves is followed by another, with the rolls at the same setting, but with the wire rotated 90 degrees. If the grooves in the rolls are very accurately made, you can actually rotate the wire and go to the next groove, rather than repeating the same size, but with many rolls, doing this will create a slight flange, so if that happens, two passes through each groove will solve that. For short pieces of wire, what I like to do is run the wire through, catching it on the other side with my free hand, and still on that side, rotating the wire and cranking the wire back through the rolls in reverse. It’s quicker than moving back around to the front of the mill and finding the same groove again.
One basic trick is that you can roll a wire part way in, then back it out, creating a step. Rotate the wire, and roll in again to that step, then back out. Now go to the next groove or tighten the rolls, and repeat, but not going quite as far. Repeated several times, you end up with a wire that’s tapered, starting large, and reducing in steps to smaller. You can then forge the steps out with a hammer or file them out, to create a smoothly tapered wire, without having to remove most of the wire with a file to get there. You can then also do things like use the flat rolls to roll that taper flat, either going the long way, or across or diagonally, to produce a flat piece tapered in width, again without having to generate a bunch of scrap. You can also set up the mill so that one grooved roller is opposed to a flat one and roll half-round wire. Start with a square wire already rolled though, to the width you wish, then reduce to half round/half square after that. With only one grooved roll, you cannot rotate the wire to reduce its thickness in both directions, so you have to start with the desired width, no more.
And you can use it for roller printing, putting sheet silver through with some lace or even cut paper to make impressions in it, as long as you don’t try to print pieces that are too wide or need too deep a texture. Paper in particular is a shallow texture, not needing a deep bite to work. Be sure to protect the rolls from the texturing material with another sheet of metal. If you do it right, you can end up with two pieces of textured material from a single pass through the rolls. Your mill is likely too light for serious roll printing in harder metals, but fully annealed fine silver is just so soft that even these mills will be fine so long as you don’t need too deep a bite to get the full depth of a texture. So some things may not work, but don’t be afraid to try them anyway. As long as you’re not usiing excessive force on the crank handle, you’re okay. You may get more things to work than you’d expect. And if you got the mill with extra rollers with patterns in them, play with them too. Just be sure that you never have the rolls tightened down tight on each other without actually rolling metal in between, as the textured roller could leave a mark on the plain roller. With wire, and fine silver, you’d have a hard time overstressing the rolls on these small mills. Where you need to be more careful, and where you’ll run into its limits, is working with sheet metal, especially wider pieces.
by Peter W. Rowe M.F.A., G.G.