Something the Average Joes have been working on. Inside the 1x3 aluminum tube are two VEXPro gears, one on the 1/2" hex output shaft and the other on a 3/8" hex adapter press fit onto the 5 mm motor shaft.
Very nice! I like how neatly it fits into the 1x3. For some reason whenever I try to do a tube gearbox it fits terribly. 
Rich
Looks very sweet!
I don’t see venting holes for the motor. Are you planning on adding some? Even just drilling holes in a few key spots will do a lot.
Good catch. Yes, the vent holes are there – you can’t see them in the picture and I didn’t include them on the layout sketch. They are mentioned in another thread, which inspired me to show what we are working on.
Since we have DRO on our manual mill, but no NC capability, we make the vents as a series of three round holes overlapping each other to align with each of four motor vent slots – twelve holes total. Easy to dial in because only three numbers are required after zeroing the DRO at the motor pilot. So it is actually less trouble to provide machining instructions for the vents than it would have been to add them to my sketch.
Rich, looks great thanks for sharing. What kind of bearing(s) are you using to support the 3/8" hex? It looks like you turned the end down that press fits into the motor output.
217-2735
The 3/8 hex adapter is drilled through 21, then drilled blind halfway 9 to make the press-fit bore for the 5 mm motor shaft. We tap the opposite end 10-32 to accept a screw and washer that will retain the bearing.
Not sure what you mean by “turned the end down”. We did face it to length so the end of the shaft is flush to the inner bearing race.
[edit] Now I see what you were looking at. In the picture, there is a lock washer (helical type) between the socket head cap screw and the flat washer that retains the bearing. That might not be needed if we use thread locker and a button head, but either way will probably work. The method pictured is easier for prototyping.
--------from the other thread----------
A 3/8" hex bore gear on the adapted motor shaft drives a larger gear on a 1/2" hex output shaft. Both shafts are supported by bearings in a gearbox housing, which we make on a mill using 1x3 rectangular aluminum tube with 1/8 inch wall thickness. The output shaft bearings are installed flanges-in with a 1/8 inch plastic spacer between the gear and one bearing. The motor face mounts to one side of the tube secured by two M4x10 button head screws, then a spacer and the shaft gear go on, and a 3/8" hex bearing (217-2735) goes in flange-out. A 10-32 x 0.5 inch button head screw and washer keep the bearing in.*