For your edification/consideration: Two scraps of angle steel, 5/15" bolts, nuts, washers.
In the photo, the bits of angle are clamping down on an aluminum hub, that is having the center bore enlarged. I 'step drilled' this piece, and observed no movement while drilling it to 5/8" diameter...
CAUTION: Drilling holes through angle steel can be hazardous to the health of you, observers or passers by, vehicles (i.e., wife's Mercedes), etc. Be VERY VERY CAREFUL!! :o