What did I do wrong?

Called a guy I met at local car show last year and brought the pinion to him. Chucked it up in the lathe and started cutting. First pass only cut the about 1/4 way in, next pass went about half way, third about 3/4, not till the 4th pass did it cut all the way. Kept going until 030 was removed. Back to .094 shim stack with at least 025 clearance and happy with the pattern. The pinion head was obviously a bit concave. I will try for final assembly later tonight.