How to cut sorbothane?

Grant, The best and probably the safest way to cut your circles is on page 2165 of the McMaster catalog (#112). Alas, the cost is ~$29.

11-15-06: Jgiacalo
First, I doubt that what you purchased is exactly the same material as
Herbie's Big Fat Black Dots. I have them and they are somewhat stiffer
than most sorbothane I've felt.

Thank you for the leather tool suggestion. It appears to be
similar in principle to the arch punch suggested by Stilljd. Do you think
the manufacturer of sorbothane makes a specific product
for a small boutique audio tweak company? I'll bet you any amount of
money McMaster-Carr stocks precisely the same sorbothane used by
Herbie. I may not have purchased the same durometer rating
sorbothane used in the Big Black Dots, but McMaster-Carr carries about
all the various sorbothane made as far as I can tell...durometer rating
(40, 50, 60, 70...), elasticity rating, etc., and in a wide variety of
thicknesses. Herbie has done all the work though, so he's entitled to
charge whatever he likes for his product. Most knuckleheads wouldn't
choose to go through the research, cutting etc. that I've done to make
their own and save $50. I don't blame them for buying Herbie's product
or the discs sold for audio use on E-Bay

Thanks Stilljd and Ronnjay for your suggestions. The arch punch is
EXACTLY the right tool, but at $39 for a 1 1/2" version
purchasing one negates the advantage of buying the raw material versus
the pre-fashioned discs offered on E-Bay and by Herbie's.

I am not sure what diameter you are looking for. How about a bulb (tulips, etc.) planter. They even come with a nice handle.

comprimise...

http://www.kabusa.com/frameset.htm?/ACCESSS.HTM

$29 for 4 sorbothane domes, 3 different densitiy options.

G_m_c, I've already made my purchase of sorbothane.