Help: Drilling precise holes

I'm building a CNC machine based on the one Robert Nansel has been outlining
in his monthly article in Nuts and Volts magazine, and I've come across an
issue.

The base of this particular machine in my case is a chunk of steel channel
that is 12"x24"x4" and .5" thick. To mount the X and Y table as well as the
upright that the Z axis bolts onto I need to drill a series of holes through
the channel, of couse the channel is *far* too big to fit onto my drill
press... is it possible to accuratly drill such holes by hand? I'd
appreciate any hints.

Thanks,
-Dan