I got used a set of boring tools and can't recall the name right off. Not something I use very often. It consists of a 3/4" drill,and a steel shaft you can put progressively larger flat cutters into,with pilots for the last size hole. With it,you can gradually drill large holes with a Bridgeport. I can't recall offhand how large they get. 2 1/2"? The set costs about $400.00. I wouldn't pay that,but got this used set off of Ebay a few years ago for much less. The type thing you never use unless you need to bore a BIG hole! I had bought one for the shop at work and used it. Except,I took a light grind along the 3/4" drill to reduce the diameter,to make it fit the 3/4" bar better,for a more accurate hole diameter with the inserted flat cutting tool.
For thinner stock,maybe up to 1/2" max.,a drag cutting trepanning tool is available. It costs money too. How thick is the material you are drilling? I hate turning copper.