E Revo Center Diff questions and Opinions

[simplechamp]

I just started making my center diff. Today I ground down the center spur gear. It was suggested to me to use a nut and bolt assembly to chuck the spur into a drill press, then use an angle grinder while the drill press rotated the spur. I didn't have an angle grinder, so what I did was chucked the spur/nut/bolt assembly into a hand drill and used that to spin the spur while I ground it down against a bench grinder. Probably took longer than using an angle grinder, but it worked out fine.

Not sure if I took off enough yet, but I was concerned about grinding too much off of the outer lip and making it too weak/brittle. Is this going to be a problem if I left the modified spur like this?