On Sat, 02 Dec 2006 11:08:08 -0800, David Nebenzahl
wrote:
Reread my original post. The drill runs without *any* sparking at low
speeds. At medium speed it runs with the normal amount of sparking
expected from such a motor. The brushes are clean and fit the commutator
well. It only sparks at high speed.

At this point, my question is a simple one. I direct this to ANYONE WHO
ACTUALLY KNOWS THE ANSWER AND CAN GIVE IT MINUS A LECTURE ON LEARNING
BASIC ELECTRICAL PRINCIPLES (which I do know):

Are drills like these wired with the field and armature in series (as it
is now) or in parallel? Simple question. (Sorry for shouting above!)

MOST power tool motors are wired in series. Heavy sparking at high
speed is indicative of bad brushes or loose comutator bars, One
loose commutator bar will not have to move much at the speed these
armatures rotate to cause arcing.

John Normile