pillar drill?

[Jonathan]

I have a (relatively) cheap pillar drill, similar to that one, and it's acceptable.
Drilling and tapping all the holes in the box section before mounting the rails is not a good plan, especially if you're marking them out by hand. For supported rails it's easiest to put bolt in the end of one rail, slide the gantry back and fourth so that they align, put a bolt in the other rail and repeat that procedure until they are well enough attached to drill and tap the rest of the holes. Drilling them in situ like this makes it much easier to ensure the holes are accurately aligned.