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