Aevald,
Thankyou sir for your research. I have never seen anyhthing like that. I have always used a Profax dd-114 brush seater and commutator cleaning stone stone sold at the welding supply to clean mine. I looked on the box and it doesnt say the make up of the stone. Ill have inquire about crocus cloth the next time Im at the auto parts store. It would be interesting to no the price difference.
Snuffman
Crocus cloth is traditionally an iron oxide abrasive. What I was taught to use on commutators is extra fine flint sandpaper, the tan/white stuff used in woodworking.
The reason for NOT using aluminum oxide or silicon carbide abrasives is in that they are rather hard & sharp, and can charge into the surface of the copper commutator or slip rings, much like charging a lap, and in doing so they will cause excessive brush wear and poor electrical conductivity.
Having said all this I have used 400 grit silicon carbide "wet or dry" sandpaper many times with no problems, I just use a well worn piece. Then I finish off with a strip of crocus cloth.
I have not done any work on SA 200 welders, the above was on alternators and power tool motors, I have turned and polished many of these, and the rules are the same.