Smoking fromm commutator?

I have had my dewalt DC925 hammer drill for a few years but is now out of warranty. It has had light usage over the last 3 years but there is now a lot of smoke coming from the commutator and you can see through the casing that the commutator is glowing hot especially in the joins of the copper segments. The brushes are fine, is there anything I can do to repair this as a new motor is quite expensive.