OT: Anyone Drill Granite

[Joe AutoDrill]

I figure some of you probably do kitchens... And thus granite counter tops... So... Anyone have a reliable chart or numbers for drilling granite?

1.25" diameter hole, 7/8" material thickness.

Looking for HP, thrust (low?) and RPM of course... Much coolant to be used I assume.

I suppose it all depends on the tooling, but lets assume an inexpensive, standard diamond tool.

Regards, Joe Agro, Jr. [phone] [phone]

[Charles Spitzer]

i have a tripod drill that i use for glass, but it's the same.

lots of water. build a dam around the hole with clay. add a touch of antifreeze in it. don't need a lot of horsepower, but diamonds like high speed, the higher the better. wherever you bought the bit would have correct rpm for their tooling. don't heat up the bit, which will kill the diamond. drill, raise up, drill, raise up, repeat. don't drill for longer than a few seconds at a time, to cool and let the swarf get washed away.

it's best if you can use a press or tripod. the bit will last a lot longer than doing it by hand.

regards, charlie

[Andrew Werby]

[Most people that do this use diamond core bits. These cut a plug out of the stone, rather than trying to remove the whole area of the hole. The best core bits use chunks of sintered diamond-bearing material on the edge, but these are expensive. Bits where diamond is simply plated on the edge are a lot cheaper, although they don't last as long. Here's a source for some: . They also have some handy tips on how to use their products, including force needed, lubrication, etc. Pros (guys that advertise Concrete Cutting and Drilling) use a special core-drill machine with a rack gear and a big motor, but you can probably get away with one of those devices that convert portable drills into lever-action drill-presses.]

Andrew Werby

[Andy Dingley]

I used to do that for drilling glass and had no end of trouble finding "clay" that was compatible with my lubricant (either oil or water) and particularly a clay that would stick in place for the second hole, over a wet surface.

So now I do it the easy way instead.

Take a piece of 1/2" plywood, an inch or two across. Drill a 3/4" hole through the middle. Grease one side with vaseline and lay it down on the glass or stone.

It's soft and greasy, not hard and hopefully sticky. Sticks to anything, doesn't care if it's already wet.

[Bruce]

On Fri, 2 Sep 2005 07:58:42 -0600, Joe AutoDrill wrote (in article ):

I used the real cheap diamond hole saws from Harbor Freight (1" hole, 1" thick green granite). As others advise, lots of cooling, slow on the plunge, RPM's up, and keep the dregs washed away.

If the hole will be exposed (not covered by a faucet flange, etc.) go real careful for the first 1/4" and don't let the bit wobble around (to avoid small corner chips)

-Bruce