[Jewelry making - Article 00054] - Re: [Orchid] Finding the center of circle

[Jewelryartschool]

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    If theses discs you are drilling are all of the same size, then I
    would make the following jig out of two pieces of scrap sheet. You
    can use brass, copper, nickel, whatever you have lying around. 

    For an example, I'll use 1/2" as a diameter of the disc. Carefully
    cut a hole into one piece of sheet that is the SAME THICKNESS as what
    your disc is going to be. Use dividers or a template to lay it out.
    You want to make it a close tolerance, not quite a press fit, nor
    sloppy when you drop in your 1/2" disc. 

    Back this plate with a solid plate. Thickness of this plate is not
    so critical. You can solder the two plates together with low temp
    solder or even rivet them together. 

    Now VERY carefully find your center in the 1/2" hole with the aid of
    dividers and drill through the backing plate. It should be a simple
    matter to slide your 1/2" disc into the hole and mark it from the
    opposite side. Use a fine pointed scribe or an automatic center
    punch. The automatic punch will probably need the point ground finer
    than what most manufacturers put on. 

    You could also make a variation on this jig that could be clamped
    into a drill press. The problem I can see with this - is how to keep
    the disc from spinning in the jig while you are drilling? The first
    remedy that comes to mind would be the use of a small pair of vise
    grips with padded or soft metal jaws... 

Brian P. Marshall
Stockton Jewelry Arts School
Stockton, CA USA
www.jewelryartschool.com
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