I just threw away over $100.00 in diamond drill bits trying to drill through a granite surface plate. I bought (2) 1/4" bits ...
First
http://www.granitecitytool.com/showi...=88&mcatnum=92
Second
http://www.ukam.com/webcatalog_drills_ordering.htm
The bit from granite city has 8000 rpm printed on the side, and the highest rpm my press will go is 3850. So I mount the water swivel and the bit and turned on the drill press. It was so off balance, the chuck came off its taper. So I removed the swivel and just went with an adapter. I did not want to dry drill so I cut a pice of pvc tube and used it as a moat to hold water. The first inch was great, and I thought this would be a piece of cake. After the first inch it stopped drilling so nice, so I stopped and cleaned the bit with a dressing stick (from ukam). Still nothing, so i pulled the bit out again, and it looks shot. So then I tried the bit from ukam and it lasted all of 30 seconds and not even a hint of diamond left on the bit at all. That was the $60 + bit. The grainte I am drilling is pink with a high quartz content.
I called granite city and Kent told me that black surface plates are very soft and drill much easier. This is for the base of a lathe, which is why I am posting this here.
My local counter top wants almost $400.00 to supply me with a piece of 1 1/4" granite 9" x 20" with a total of (20) 3/8" holes drilled through (the smallest they can drill is 3/8").
Back to the drawing board.