williamhenry wrote:
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


The OP didn't say *how* centered and parallel it had to be, or for that
matter the length of the bolt and it's threadrd length. One man's idea
of "crucial" centering may be different than another's.

He might be able to use your idea but beat the cost of buying a tap and
tap drill if he doesen't have them by just drilling a 1/2" hole through
that plate and securing the bolt with a nut on top, or one on top and
one on the bottom, depending on the bolt's thread length.

Heck, he might even beat the cost of a thick metal plate if he doesn't
have any by using a thick hardwood board and some washers under the nut(s).

HTH,

Jeff

--
My name is Jeff Wisnia and I approved this message....

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"