Never tried it, but "sober brain-waved" it. 

Clamp a piece of timber to your drill press, lock the table... use the relief hole method (if you don't already do it) to cut a circle that the ball can sit in without bottoming out on the table top.  The quill should be perfectly centered on the circle (unless you used an oval circle cutter) ... place the ball in the circle and drill a perpendicular hole... just don't forget to replace the holesaw drill bit with your chosen gauge bit (and the holesaw may also inflict some minor damage to the ball if you forget to change... and it'd be a bugger to hold still)...

If your first cut is too short... Take the second cut from the longer end... LBD