[Jewelry making - Article 00661] - Re: [Orchid] Rolling mills square wire grooves

[Peter W . Rowe]

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>     Does anybody know why the square wire rolls in every mill I've
>     ever seen (dozens) have flat bottoms to the square wire grooves? 

    Lots of other answers have suggested various reasons, but I suspect
    the best answer has not yet been given, or if it has, I missed it. 

    When you roll wire, you're going from one size, and then to the next
    size down in the next groove. The rolls only compress the wire
    vertically, reducing the vertical or roll-to-roll dimension. they do
    not make the wire any narrower in the horizontal dimension. In order
    to progress from one groove to the next smaller size groove, the wire
    has to be no wider than the new smaller groove, or it will pinch in a
    nasty flange along the sides. The flats at the bottom of each groove
    mean that after you roll the wire through a groove, the measurment
    top to bottom, across those two small flats, is smaller than the
    width of the wire measured side to side. Those flats are sized so
    that this difference equals the reduction in groove size between one
    groove and the next. So you turn the wire 90 degrees before going to
    the next smaller size groove, and the flats now mean that the width
    you're putting into the groove matches the width of the new groove,
    but the new smaller groove rolls the old wider dimension thinner,
    whilst putting new small flats on, ready to be turned again 90
    degrees for the next smaller pass. If you turn it 90 degrees and put
    it through the same groove, you now end up with a cut corner square,
    which is much better for subsequent drawing than a fully square
    cornered wire would be. It doesn't need too many passes through the
    appropriate plate to become either fully square in a square draw
    plate, or round in a round plate, etc. 

    But the main thing is simply producing a rolled wire with dimensions
    that physically can be fitted entirely in the next smaller groove.
    Fully square cornered rolls would simply not work in a two rolled
    rolling mill. The so-called "turks head" drawing fixture can be made
    with rolls instead of adjustable friction plates, and I saw one once
    that was an actually motorized rolling mill, with four small rolls
    arranged to produce an adjustable dimensioned square or rectangle
    sharp cornered wire. Because all dimensions were being reduced
    simultaneously, no flanges were being produced. But the design, at
    least the one I saw, was difficult to adjust and operate, and quite
    slow, and could not handle a large reduction in size per pass... It
    was intended more for producing a single precise dimension of wire
    rather than reducing a larger wire progressively smaller... 

Peter
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