Sparks in Motor Housing

[caroj59]

The motor on my table saw has started sporadically slow down then speed up. I noticed sparks inside the motor housing when this happens. Do you think its the armature, field or speed control switch?

I don't want to start replacing parts until I am sure.

Any ideas

[qdea]

firstly you can try replacing the brushes cause after a while when the brushes get short and they are not making proper contact wit the commutator sparking or arcing would occur.

then if that still dont work,possibility is u need a new armature