I'm concerned from the title that there may be a perception that it's acceptable to oil the commutator/brushes...but not to excess?
Forgive me if I've misread, but oil has no place on the commutator surfaces. Passing an electric current through an oil film...even a very thin oil film...will cause the sparking/smoke which will result in generating carbonaceous residue (the black stuff) that ultimately affects performance of the motor.
Now, more likely oil on the commutator results from over-oiling the motor shaft bearing adjacent to the commutator. Some older motors had wicks leading to the bearing. Oil...a single drop or two...would be applied to the wick, from which the bearing would receive its necessary/adequate lubrication.
Other motor designs might have a 'spinner' washer between the motor bearing and commutator. The idea was that, if excessive oil was applied to the bearing shaft, as it migrated to the spinner washer, the excess would be flung off (to the surrounding other parts, interior) rather than continue to the commutator.
Of course, in the interests of cost containment and (
) so-called 'planned obsolescence' (give the repair/parts guys something to do.) the ultimate refinement of motor designs was to ditch all those design precautions related to excessively oiling motor bearings and...hey, it's good enough.
Words (FI, "A single drop or two is sufficient"....but, of course, more would be better...like smoke fluid?
) were included in the instruction manual. Oh, right...'What instructions?'...'There were no instructions included...I bought this at an auction, train meet, flea market, garage sale, guy with a trench coat, sunglasses, and fedora,...!
But, perhaps, I've digressed and misread...
Sorry.
KD
