A motor needs to be a universal type or series wound motor to use a
The motor will have brushes and can run on AC or DC. This is the
type found on standard Dremils, Foredoms and the Foredom polisher.
DC motors can usual have various types of speed controls- Ac only
motors generally not.
The bigger motor polishers are induction type and and are AC only
have a fixed speed and will not work on a rheostat.
There are ways to change speeds on some types of AC motors but this
is not a common thing you can do.