Can a stock TM gearbox be modified to use 7mm bearings?

[pinoyboy]

Thinking about getting higher ROF by goin with some bearing bushings. Has anyone tried this? If its only 1mm wider, it shouldn't be that hard to modify, or am i wrong? thanks in advance

[ILLusion]

Drill press, a jig/fixture and a 7mm reamer.

Or bring it to a machinist to do it.

Or buy a gearbox that's already done and sell your old gearbox

If you don't know what you're doing, I don't recommend doing it yourself. If you get the hole off centre, you'll screw up the axle alignment and as well, the gear teeth alignment.

[pinoyboy]

If I use a drill press and and some clamps to hold the box down, would the holes be like a pilot hole to help retain a centered hole?

[mcguyver]

I tried to do this once last year with a reamer and drill press. The problem that I ran into wasn't getting the hole size corect and centered, but rather the "flange" on the bushing. It needed to be recessed more into the mechbox than what the original 6mm ones were. It extended too far into the box and was very tight on the gears with no shims in the box. this would have required very fine countersinking around an already thin hole to make it work and rather than try it and waste a bunch of time, I just abandoned the project and got a 7mm box to work with instead. I'm not saying that it can't be done, I just feel it's more effort than it's worth considering the cost to you in U.S. $$$ and any potential benefit of just outright buying a 7mm box, which will be reinforced anyway.

[bruce]

If you have access to a milling machine and end mills, it's an easy mod to do. If not, buy a 7mm gearbox.