The dremmel tool is a series wound motor, and it is ideally suited to control by a SCR, (silicon controlled rectifier) which is the working stuff in a dimmer switch. It's actually better for the motor than a resistance type foot control pedal, like from an old sewing machine. The only caveat is that it may unduce back voltages, that destroy the dimmer. That's why most dimmer switches state clearly that it is only for an incadescent (resistance) load. It amounts to a six dollar experiment that usually works just fine.
Induction motors, unless they are specially made, will tend to overheat when slowed down by a dimmer switch. That is because their speed is regulated by the frequency of the power and the winding configuration in the motor, minus shippage. (A 1725 rpm motor is really 1800 slipping 75 rpm.) A ceiling fan motor is wide, and has a lot of ventillation to help it dissipate the heat of excess slippage.
The way to tell them apart is that an induction motor doesn't have any brushes in it. Induction motors hum, and series motors whine. Drills, vacuum cleaners, hand saws, etc are all series motors. Washing machine motors, refrigerators, table saws are all induction motors.
Hope this helps
jm
