clamp a piece large plate to the drill table

about one inch thick would be fine

drill and tap it for the bolt
use a undersize tap drill and a real sharp tap
might even hone the tap a few thou under size for a tight fit on the bolt


thread the bolt into the hole from under the table
use a nut to lock the bolt in place

drill your hole

will be as centered as practical on that type of machine

be sure to use a good sharp center drill to start both holes

good luck