Commutator replacement/repair

[randy.bopp]

I just recently acquired a 1920 model T and found that the commutator is starting to stick real bad. Now it will not even move using the advance lever.
How do you lubricate or replace it? It appears that it is held on by a clamp from the generator and if I remove the clamp it will come off. Is that correct?
Do you have to remove it to lubricate it?