For a few prototypes you might try a hole saw in a drill press. If you
just have a hand drill, maybe clamping the metal between a couple of
sheets of fairly thick plywood would keep the hole saw from wandering.
( You would have to drill thru one piece of plywood first, but you
could use a drill in the center of the hole saw when you do that. )

After you are sure of what you want, you might be able to make a die
set using a drill bushing for half of the set. You could probably use
a vise to apply the pressure to cut out disks out of thin material.


Dan