Piece of brass will be fine, may not last so long as bronze but when you have done it once you will easily replace if worn, which will be a long time. Can't rememeber where I found the piece of brass, maybe off the stem/cylinder nut from an old oxy guage or something like that. Would a selector out of an old car gearbox be any good? Try scrap yard or I'm sure I could send you a piece if your stuck, I hoard what looks to me like useable brass and very seldom use it.Great idea of using car body filler. I haven't started to take it apart yet.
I was wondering where to get a bit of bronze, then literally as typing this remembered the piece of brass left in the chuck to demonstrate it cutting. Would brass be acceptable?