In attempting to make a couple of hubs this year, we bored out some aluminum stock, like ya do, on our lathe. We used a 1/2" bit since the motor shafts are a 1/2" diameter. However, the holes were too press fit for our liking -- we wound up having to sand down the motor shaft a bit in order to get the hubs on the motors.
In the future, I'd like to alleviate this. I've noticed that AM's sprockets and some gears come with a 0.502" hole -- which is great because it takes no effort to put on and remove their hubs (well...most of them

). However, in my searching I've come up blank thus far in looking for a drill bit larger than a 1/2". Any suggestions? I'd like to find a better solution than grinding down a shaft.