Old dentist drill

hello, i’ve recently baught a couple of old dentist drills. They
are Emesco and of the pully variety (belt driven handpiece). when i
run them I can see parks trailing off of the brushes. It is much
more evident on one than it is on the other and I was wonder if
this was normal (doesn’t really smell normal) and what should i do to
fix it?

thank you,

Kiddmann, HI

A small amount of sparking is ok. The armature that the brushes rub
on should be almost chocolate brown. If there are any black marks or
pits you should remove them with fine sand paper, not emery cloth as
the particles are conductive. That type of motor is called a
universal motor, it will run on ac or dc.

Hope this helps.
Bsilver head (old uncle Milty)

The old dentist drill motors and the flex shaft motors will spark
less if the brushes are replaced often and the armature commutator
copper segments are “cleaned up” with fine grit sand paper. Here at
the Jewelry equipment Dr. we start with 600 grit and finish it with
1500 grit sand paper. Please do not use sand paper more corse (lower
number) than 600 grit.