I will be watching this with great interest. I have drilled and epoxied tapped inserts into a 18 24 4 surface plate and bolted up the ballscrew and rails. I am currently laid off, and cannot go further until I find steady work. Did you drill dry, or did you use a water swivel?
I used a (leaky) water swivel, that i had to put a bag over with zip ties, but it was still a messy job. I could not believe how easy it is to drill granite. What will you be using as a headstock? Will this be a gang lathe?