Replies

1. 
   BarryO | Nov 03, 2004 03:19am | #1

   I think your looking at a diamond hole saw here.

   Not cheap.  'found this with a Google search:

   http://www.masterwholesale.com/hole_saws.html

2. 
   UncleDunc | Nov 03, 2004 04:41am | #2

   Ditto on the diamond hole saw. You can drill granite (or glass, or anything hard and brittle) with brass tubing, loose silicon carbide abrasive, and water, but by the time you track down the proper size of tube, and the fittings to adapt it to your drill chuck, and the SiC, the diamond hole saw doesn't look all that expensive after all. Here's a site that has one for $54. (Not a recommendation, just an example. It is the first one I found with Google.)

   http://www.tiletool.net/hole_saw_diamond.asp

3. 
   WayneL5 | Nov 03, 2004 04:50am | #3

   A diamond hole saw is the best method.  They can be rented.  The saw itself is heavy and will scratch the surface unless you put some protection underneath.  The protection can't allow the saw to bounce around, so something like a piece of Kraft paper would be good.  The bit needs pressure to cut, but it is a slow, patient process.

4. 
   DennisS | Nov 03, 2004 05:39am | #4

   Jeff -

   A diamond hole saw like others have suggested is the ultimate answer. I've tried drilling holes in stone, even glass with a brass pipe and valve grinding compound (the kind of stuff they sell in auto repair shops) - this can be done but it's hellishly slow and, for a counter top that's probably at least 3/4" thick, bring your lunch and a good book.

   You can probably do it with a good heavy duty 1/2" drill motor and a diamond hole saw but understand, getting the bit started accurately and keeping it that way is really tricky. Does whatever goes through this hole have any kind of an escuchion plate to cover the raw edge? I can almost guarantee you that you'll have some small amount of chipping around the edge doing it by hand. Build a dam out of clay or something to hold at least a small puddle of water to lubricate the bit and help carry away the waste material. If you have the luxury of some scrap granite lying around it would pay to practice to get the feel of the operation.

   The other option is to rent such a machine as what comes with a stand that holds it (moderately) perpendicular. These are called coring machines and are used extensively to drill holes, large holes in concrete slabs and walls. They do have smaller bits. They're exceedignly heavy. They have a vacuum platform that holds the machine to the slab of whatever you're cutting so you can put leverage on the motor to effect the cut. Takes lots of water. I wouldn't advise doing it in a finished space! (hehe) How do I know - I just recently had to drill (core) a 4" hole in my garage floor for a new water service line.

   I'd say if I had to do this I'd rig up some kind of drill stand that I could clamp or secure to the granite then I'd purchase a diamond hole saw. Master Wholesale (in Seattle) sells a 1 1/2" premium diamond hole saw for $US54.68.

   http://www.masterwholesale.com/

   Enter hole saw in the search box.

   ...........

   From Beautiful Skagit Co. Wa.

   Dennis

1. 
   WayneL5 | Nov 03, 2004 06:49am | #5

   Core drilling without a machine is difficult, because there is no feature which keeps the bit centered.  If it touches down just the tiniest bit off perpendicular, the bit will walk across the surface.  The machine also provides cooling down the center of the bit, which flushes the swarf from the cut, allowing faster cutting.  Cooling from the outside isn't bad, but you don't flush the swarf well once you get down into the material.  The very hefty weight of the machine is an advantage in keeping it in position.

5. 
   Scott3 | Nov 04, 2004 06:59pm | #6

   Jeff, your best bet is to contact your local granite fabricator and hire them to core this size hole you need in your granite. Your posting doesnt say if the stone is small enough to transport to a stone shop.Also doesnt mention how thick the stone is. Countertops are typically 2-3 cm thick. 3/8 thick tile you might get through.We usually charge around $50 for this service performed on site. Takes about 10-15 minutes. You will spend all day and several expensive drill bits and still not get through stone 2-3 cm thick. You need a diamond tiped hollow core hole cutting bit with a water cooling source to effectively get this done. If this is a valuable piece of granite it is well worth the money spent. Good luck.    Scott

1. 
   JeffreyS | Nov 05, 2004 02:55am | #7

   Scott,

   Thanks for the input. From the other postings that was pretty much my conclusion. I think hiring a granite fabricator to do it seems like the best route. Especially if the cost would be less than $100.   This is a built in countertop that is part of a desk.  The hole is being put in to allow power/phone cords to go through. I don't know why the original plan did not call for them (I did not own the house at the time).

   Jeff

1. 
   joinery45 | Nov 05, 2004 04:08am | #8

   Use a diamond bit. Cut a whole in a piece of plywood the same size as the OD of the bit.Put some  caulk around the perimeter of the hole then clamp ply where you want the hole. The caulk keeps the cooling water in place and the ply keeps the bit from skipping around. Thats the LAST thing you want to have happen.

   Thanks

   John