Bill, they both look serviceable, as is.
Really no need to polish, as there is minimal grooving.
That said, I have seen some emery paper that is actually electrically conductive. Crocus cloth has a biding agent for the rouge that will attract carbon dust as the brushes wear.
Both are bad news, creating possibilities of a short bar-to-bar. (That's what the brush does momentarily, until they contact the next segment, and so on...)
Aluminum oxide is non-conductive electrically.
When I referred to polishing, I meant chuck it in the lathe, and spin it about 500-700 rpm and polish it while rotating. You want it as round as possible.
Concentric to within .002-.004 T.I.R. is mostly acceptable. One high bar, or two directly opposite each other could mean a stall condition, but I see no evidence of that in your pics.
A low bar, burned and pitted at the slot, possibly less so directly opposite, if at all, indicates an open coil (usually at the coil-to-comm connection, called the riser.)
Any of these conditions will cause arcing when the brush makes and breaks contact with the comm, leading to rapid brush wear and decreased performance.
In other words, if the opposite sides look as good as this side in the pics, you should leave them alone. The brown film you see is a good thing. that actually is a conductive deposit from the old brushes and no real need to disturb,(unless it is OOR)
Did you locate your brush caps? Generally the brass ones are used to create a current path plastic might not provide. In a pinc, one coul use a brass washer between the cap and spring to accomplish the same thing...
Jeff in Lone Star, TX
PS. I'll post a couple pics of what I was referring to later. It's 105 in my shop, and I am DONE for today!
