[EricH]

Originally Posted by Rauhul Varma

That would mess up the center to center distances.

That is true. On the other hand, part of design is designing for what is available. If the only available gear is .020 larger than needed, then that needs to be considered. Center-to-center shouldn't affect it--matter of fact, I'm specifically suggesting changing the center-to-center BECAUSE the center-to-center is too small for that gear, and the only thing a center-to-center will affect is where on the gear contact is made (though, that little detail can introduce some backlash, among other things). That can also be mitigated by playing with a few other things--for example, if your center-center is exact distance, most FRC folks will add 2-3 thou to that to account for manufacturing tolerances; if you make it 10 thou instead, you've really only added 7-8 to what is normally done.

Personally, I wouldn't attempt turning down a gear once it was cut, for the reasons listed above--there's too many things that could go wrong, minor enough it would seem, but just too many items to tempt Murphy and his gremlins. That goes for both a mill and a lathe, BTW. If someone really knew what they were doing, then that could work, but in FRC, those types of folks are rarer then we'd like to think, unfortunately.