Years ago our washing machine packed up - brushes worn out.
I bought a set that lunchtime and stripped it down that evening. The commutator was badly scored, and so I thought I would have to get a friend to skim it on his lathe the next day.
But why wait. During my apprenteship, I learnt how to file accurately, so why not file it. Three hours later, I had a nice clean (and round) commutator. Brushes fitted and it was working fine, and dis so for six more years.