I'll explain why I'm studying wheels in my next post. But for now: I studied some wheels.
More precisely, I bought a whole bunch of small rubber-treaded wheels from McMaster so I could measure them (McMaster doesn't have CAD of their wheels, which is annoying). I needed to be able to core out ~73-75mm of the hub.
I bought these: 2337T35 , 2337T42 , 2337T37 , 2829T68, 2829T56 , 2439T42 , 2243T22
All 4in wheels of varying widths and materials. I got them in and measured their hubs and 5 had hubs that were large enough, and only 3 of those were reasonably priced or would work for me (2337T42,2337T35,2829T68). Interestingly, the wider the wheel got, the smaller the diameter of the hub...no idea why. I like the super soft tire (2243T22), but it was really rounded, and I'm planning on putting multiple tires on *ahem* something.
2 of the 3 wheels are mcmaster's "Rubber Wheel" series. They are black phenolic? hubs with black rubber tread. The other one is "Performance Rubber-Tread"...actually Colson Casters! Nylon or polypropylene? hub with grey tread.
The phenolic ones are easy to machine...not nice, but easy. Phenolic is probably the WORST smelling material I've ever tried to cut...mix of shit and rotting vegetation. In fact, I gave up after a few passes. Even though the wheels are a lot cheaper, it isn't worth dieing for...
So I tried the Colson. MUCH nicer. Super easy to cut, and NO smell. Found my wheel!