>I'm not really sure which is the best way either to be honest. Cutting
>against a flat surface means that the center of the circle is left
>untouched, which is what we care about. Wouldn't a punch/die system
>possibly mangle the inner part of the circle? FWIW, the flat surface
>is some sort of plastic material, it might be Delrin. That way it
>should give slightly.

No flat surface. Every punching operation stresses the material up to a
point. You sound like you need a female punch and male die (the reverse of
what's used normally). This leaves a small kerf on the disk and a large
bevel on the scrap. Also the disk has nowhere to fall unless the whole
machine is horizontal or similar (the punch axis would be horizontal).
This is also unusual but do-able.

Peter

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