What would cause this?

[BrianG]

Well, two things that I can think of:

1) Not being hardened will eat those things up fast.

2) Tooth shape. Not all Mod1 pinions are the same. If you look at Mike's old pinions, they have a different shape than the ones he has today. The old ones were made to use with a plastic spur and are shaped accordingly for proper mesh. His current pinions, along with being hardened, have a slightly different shape so they work well with both plastic spurs and steel spurs.