You can, of course, use just a single machine by changing the laps,
using a different lap for each grit. Unless you are doing continuous
production, that is the way the machine is generally used. The machine
has a tapered spindle and the lap just threads itself onto the arbor.

If I were you, I'd call a few of the makers, tell them what you want to
do, and see what they have to say. Elaine Corwin (? sp.) at Gesswein
is a frequent contributor to the online jewelry forums, and was able to
answer a number of questions for me when I was looking to buy a
magnetic finisher last year.

Regards,

Bob