Cutting holes, which tool?

[Kenny]

So I have a diamond drill bit 1 3/8 Diam with a shank to fit a drill.  I am trying out everything on scrap pieces and found using a power drill it is very slow to drill through a 3 cm piece.  It took me about 1/2 hour and lots of pressure and I used water.  That sure seems longer than your bit you have advertised that does it in 3 or 4 minutes.  My question is should I be using an angle grinder at a 11000 RPM or is it correct to use the drill?  Maybe I just have a bad bit but I am concerned that with the pressure I needed I could easily break the granite around the sink when cutting. Thanks for the advice!

[Mark D.]

Kenny,
what you are describing is a tile bit.
They have a post on them and are made for cutting through tiles, not slabs of stone. They won't take the excessive heat and pressure of the drill when used on slab. You can get away with it but it is not the tool of choice. The one you are describing with the post for a drill should look like this:



The fabricators we deal with use a coring bit on a grinder. These bits will cut through 3cm granite slabs in about a minute, and you should get 100 holes out of each bit. They have a 5/8"-11 threaded arbor to fit on a grinder and can be run with or without water. They are made for production and look like this:


You can get them here:
http://www.defusco.com/Diamond-Products-Drilling-Solutions-for-Stone,-Ti-Dry-Segmented-Hi-Speed-Stone-Cor/c25_497_680/p2150/1-3/8%E2%80%9D-SEGMENTED-SLAYER-STONE-CORE-BIT/product_info.html?osCsid=4c775plohcg31b67epkaab9mi0

Glad to be of service,
Mark

[Kenny]

OK the first one you show is what I have so that explains why it does not work.  I was actually looking at the second one you show and will use it.  Thanks very much!