[Jewelry making - Article 00814] - [Orchid] Rolling Mill Basics - The Square

[Jay Whaley]

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Orchidians,

    This forum is all about sharing, and since much of my teaching for
    the past 30 years has been about the rolling mill, I thought that I
    would put out some information regarding how to use it. I am planning
    to put out a weekly "How-To" tip on a particular aspect of the
    rolling mill, and I hope some of you will find it useful. My
    suggestion would be to practice in sterling silver, as it rolls
    beautifully, and is cheap enough to experiment with. 

    Ground Rules... Your rolling mill should ideally be a combination
    mill. Said another way, it needs to have both flat as well as grooved
    rollers. Making half-round stock will most likely need side rollers,
    if that is an option on your mill. The rolling mill rollers should be
    very clean, unpitted, and wiped free of surface grit or oil. DO NOT
    run your flat rollers all the way together. This is not necessary,
    and can lead to roller damage if small bits of metal or grit get
    trapped between the stuck rollers. Making wire stock with rollers
    touching is guaranteed to produce "fins" on your wire, which is
    usually undesireable. Make sure all metal run through the rollling
    mill is annealed(soft) and DRY. 

    "The Basic Square" 

    This wire shape, the Basic Square, is the start to making all wire
    and bezel stock. When planning your "goal" wire or bezel shape, you
    need to know what it's final dimension will be, both in width and
    thickness. Your poured round ingot, ideally, should be wider than the
    final shape you want to end up with. ( However, there are tricks to
    widen this if needed) Start with your mill open, and visually find
    the groove which "matches" your ingot. If anything, you want your
    round ingot to appear slightly larger that the groove you are
    starting in. During the first roll through the mill, you should feel
    a light pressure on the handle, and should see small flat areas form
    on the ingot when run through. This first pass is just to get the
    right adjustment on the mill. 

    For ease of description, let me describe this "square" shape we are
    making as having a 3-6-9-12 orientation, like the face of a clock. As
    the square stock emerges out the other side of the mill, it will have
    pressed both the top and bottom corners of that ingot, the 12 o'clock
    and the 6 o'clock position. Now, you will want to run that same ingot
    back through the same groove, but now pressing the 3 o'clock and 9
    o'clock position, or the other corners you didn't press the first
    time through. Stay in the same groove. The CORNERS of this square
    shaped ingot will always be facing UP when going through the grooves,
    not the flat sides up. Without re-adjusting the mill, you will have
    run the ingot through the groove, and before running it back through
    the same groove, you will have given it a quarter turn, so that by
    running it back and forth through the mill, in the same groove, you
    have pressed all four corners, making a square shape. 

    Now, turn the top adjusting handle on the mill a half turn closed (
    counter-clockwise ). Repeat the rolling of the ingot through the
    same groove, and back through the same groove, after having turned
    the stock a quarter turn before that return roll. The ingot is now
    getting a nice, regular square shape. If your final shape needs to be
    narrower, then run through the same groove after having tightened the
    mill another half turn. With sterling silver, you can easily make 3
    back and forth passes, adjusting the mill closed a half turn before
    each set of passes, before you will need to anneal. During this
    process, if the rollers start to touch, then open up the mill a few
    turns, and start the process on the next smaller groove, starting
    that new groove with minimal pressure to get the adjustment of the
    rollers right before "committing" the entire wire to the mill. If you
    see FINS forming on your stock, then you are in the wrong groove,
    pressing it way too hard, or trying to go way too fast making your
    wire. 

    All metals will have different "personalities", regarding how much
    you can roll between annealings, as well as how much you can tighten
    the mill between passes before getting stress fractures. "Practice
    Makes Perfect", as they say. 

    A word of warning about gold alloys... there are 2 basic alloys, one
    for casting, and one for rolling. The casting alloy is too brittle to
    roll, but the rolling alloy can be cast. Any amount of casting alloy
    in your ingot will very likely lead to cracking, in my experience. I
    only buy rolling alloys, for both my casting and rolling needs. 

    Next Week..."Tapering Square Stock for the Draw Plate" 

Jay Whaley UCSD Craft Center
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