I realize this is not responsive to your question but.....IMNO circle
cutters are very highly overated. I doubt you will have much luck cutting
neoprene with one anyways. How about finding something the correct diameter
and sharpening it enough to turn it into a crude die cutter. I have done
this using tin cans, tube and pipe. The only way to control the speed of an
induction motor is with a frequency changer.
Dave