Wavy commutator??

[OperaHouse]

I worked on a friends German orbital pipe cutter yesterday. The control was
going into over current motor fault. The brushes were heating up even with the
motor removed. Brushes had a sticky buildup on the sides. Resolving that did
not correct the problem. Tore it apart further to look for any tel tale failure
of the armature. The commutator cleaned up to factory condition with just a
couple light turns of Scotchbrite. That did not resolve the issue.

This motor assembly seems to be derived from a hand tool even though the importer
wants $1500 for a replacement. The armature is a high quality build. What I don't
understand is the commutator seems to have these waves machined into it from the
factory. These do not appear to be from wear. Only the lightest of buffing was
required to make this look like new. I have never seen these waves in a motor
commutator before. Seemed to have about 10-15 ridges evenly spaced.Is this my
imagination or is there a purpose to this?

This was just a quick social visit and they bought another motor to get back
production. I'll probably get the motor in a week or two to look at again.