Unfortunately, I do not have a 'before' picture, but I have taken shots of the repair process.
The first picture here is the final result.
Kind of a tease, no?
Step 1: Rebuiding A DC Motor Commutator: Clean up the Commutator Shaft
I secured the output shaft end in the lathe-chuck, and to ensure true turning, I places the commutator end of the shaft in a bushing held in the tail-stock chuck.
It took some very careful cutting, but I was able to remove very little of the insulating core material, which appeared to be phenolic.
Note that the 'lugs' on the left of the phenolic are the wiring attachment points, and the 'ring of dots' on the right are the sad remains of the commutator sectors. In most commutators, the sectors are molded into the core, with tabs or under-cuts. The 'beads' on the right are well embedded into the phenolic core.
The 'lugs' are beveled to help with soldering adhesion of the new sectors.
BTW, the phenolic diameter is just under 1/2"! (1.2 cm)
Step 2: Rebuiding A DC Motor Commutator: The new Commutator Sectors!
The copper ring was selected to have a very close fit (almost press-fit!) to the phenolic core.
The ring was cut from a copper-pipe reducer, intended to receive a 1/2" nominal Cu pipe.
Note the bevel inside of the copper ring. It is a soldering thing!
Step 4: Rebuiding A DC Motor Commutator: Prepation for Soldering....
Note on the solder!
Lead free, high-melting point stuff.
Stronger than tin-lead, by a bit.
After tinning, I used solder-wick to remove excess solder, as too much would not allow parts to fit properly.