I'm working on a go cart as a school project with a friend. Our budget
is extremely limited, so we're leaning towards machining our own wheel
hubs. I have a HF minilathe, 1/2" drill press, and a 120v lincoln mig
with c25 and straight argon, so welding aluminum is possible. I'm
wondering what kind of accuracies would be required. Bolts will be at
a 4" circle, tire diameter of 6-8" at a speed of up to 25 mph, I'm
calculating 120 rpm (is that right?). Although this is kind of low,
I'm affraid the heavy radial loads may damage the bearings, especially
with no suspension. I'm confident I can hold 20 thou tolerances with
the setup I have now, but is there anything else I should consider?
I'm using the stock three jaw chuck, with HSS. I have a few boring
bars for the bearing. I don't have a rotary head or cross slide vise,
but have a wiggler.

An example can be found at
http://www.mfgsupply.com/m/c/53-681.html?id=XGPPnfW9