All of the suggestions are spot on, I wanted to cut some 3 - 1/4" slate for calls from some old roofing slate, I bought one of the diamond dusted hole saws. I clamped my slate to a piece of plywood, ran water over it as I applied pressure to the hole saw, running the slowest speed on my drill press around 100 rpm, and it worked great. If you are gonna cut holes then I would suggest doing a combo of what Wendell and Scott were saying, place it between two pieces of wood, then slowly drill down, let the drill work. If you are getting chips or break offs, you could try to reshape the drill bit cutting degree to around 60 or barely and lightly take the very outer edge off the cutting tail, this is where a lot of grabbing comes from.