Yeah Tim, I used a 1/2 inch drill and the blanks are just under 3/8's. They do lose some wood when they are fed through the first set of holes. I think the aluminum will hold up pretty well, but if it wears, I will use a reamer to open up the holes and use some bushings if I can find the right size.
Hey, on the bullnose bit you are talking about 3/8's diameter, not radius right?