Cutting Granite

[Mike OMelia]

OK, not wood, but thought someone here might know. I have to expand a hole where my cooktop is to accomodate a new cooktop and downdraft ventilation unit. The part to remove is about 29" long by 3" deep. Finishing the stone face is not needed. What tools (bits & blades as well) do I need?

Thanks.

Mike

[Henry Ambrose]

A Rotazip with a diamond wheel will do it. It will be very messy - a helper with a shop vac held close to the cut will suck up some of it. Clamp a piece of wood along the cut to help keep from over cutting.

[Jamie Buxton]

Or a 4" angle grinder with a diamond blade. That's what I see the pros using. You can get the blades at Home Depot and the like. The pros cut the granite outside whenever they can, because it makes nasty dust -- gritty stuff, unlike nice wood dust.

[Maurice Ungaro]

Mike, the CONTINUOUS RIM diamond blade is a must.
Also.....WEAR A GOOD MASK and VENTILATE WELL. Granite dust is worse than MDF dust. More than a few folk songs were written about the old "hard rock" miners, and their resultant respiratory problems - silicosis I believe.

[Jim Rimmer]

From videos I've seen I can only imagine the amount of dust that will be generated. A few years ago we had to have a couple of tiles replaced in the kitchen and the moron that was sent to do it grabbed a grinder and took it to the grout (while no one was home) to remove the old tile. That dust went EVERYWHERE, even inside the cabinets.:eek: So, do all you can to mitigate the dust is all I can suggest.

[michael case]

Maurice is right Granite dust is dangerous!

[Maurice Ungaro]

IF you can drip water on the blade as it is cutting, you can negate a lot of the dust problem. But, as the granite is already installed, the water trick may be...well....tricky.

[Mike OMelia]

Maurice, what is the blade attached to? (the tool).

As for the dust, thanks for the heads up. I will build a "tent" around the island with plastic and simple framing.

Mike

[Jeremy Brant]

I haven't used a rotozip before, but for rough cuts a diamond wheel on a 4 or 4.5" angle grinder works fine too. Again though, lots of dust.

[Maurice Ungaro]

Mike, the Roto-Zip may be under powered. Personally, I try to cut my stone with a circular saw (Skil-saw type). More power, bigger blade. The bigger blade cuts more efficiently, and you can make a quicker job of it with the increased power.

If you are tenting the area, try to use water to mitigate the dust. Simply have an assistant use a pitcher, or 1 gallon jug (if a garden hose is not applicable) to place a small stream of water in advance of the cutting wheel. This also helps cool the blade. Again, with an interior job, this may not be practical.

[Mike OMelia]

Skil-Saw? Really? So the idea is to make several passes, and increase the depth each time?

Yes, indoor project. Water is out of the question.

Mike

[keith ouellette]

I had to cut and polish some granite for a fire place hearth. I used a circular saw and a diamond blade.

Don't use an angle grinder if you want a very straight cut.. Unless you have a large one it won't really cut 3" anyway.

If it is a plunge cut the plunge part will take a while so be patient. after that it's a piece of cake. maybe 2 passes. what I cut was only 2" thick. 3" seems like a really thick counter.

Do you have to do it inside? If you do you should use a 120v dc, vented outside and have a helper hold flexible pipe to catch the dust.

There will be a lot of dust and a shop vac won't cut it unless you don't mind dusting off everything in that part of the house.

If you can section off the kitchen with plastic it would be a good idea to do so.

[Rick Hall]

If you hold a large grouting sponge that is fairly damp right at the back end of the spinning blade it will work well to catch most of the dust as it comes off. Go slow and re-wet the sponge every few inches. Just have to be extra careful since you are playing with water and electricity. I have a gfci protected power strip I use when I do this.

A 4 1/2" angle grinder will work fine so long as you take it in a couple of passes, instead of doing it all at once.

The helper with a shop vac plan also works well, but make sure you have a fine filter in the shop vac or you'll just pump the dust back out.

My day job is tile & stone setting, and I cut grout and stone all the time.

Rick.

[Jeff Nolan]

the guys that installed my granite counter tops used a skilsaw (worm drive) with a continuous rim diamond blade. They even used a small hose to dribble water into the cut as they were going... I wouldn't believe it if I hadn't seen it with my own eyes. Probably won't work for you given that it's already installed but if you can control the dust I would definitely go with a skilsaw.

[James Stokes]

The best way I have found to control the dust is get a pressurized pump up garden sprayer. Have your helper in front of you spraying continiously The granite and blade. You will end up with a sludge to clean up but that is much easier than the dust.

[Edward P. Surowiec]

I cut a kitchen sink "cut out" in a six foot granite counter top. I was able to do the work out doors. First attempt was with a $40 diamond Rotozip bit, it took forever just to bore through the 1" granite. I switched to a 6" diamond tile cutting blade and my cut-off saw for the long straight cuts and completed the rounded corners with a 2" diamond blade for RotoZip. As everyone above has said Dust , Dust , Dust is a big problem. I wore a mask, glasses, and worked in the rain and the dust was very bad.

[Mike OMelia]

Everybody keeps saying skilsaw. In the South, we say coke for coke & sprite & etc. So, does this mean any capable circular saw?

Mike

[Ron Fairbanks]

Hi guys and gals, just coming off 15 years in the ceramic and granite tile market moving into the engraving market. My experiance with granite cutting shows this to be the safest and fastest way I've seen. I'm assuming that the sink cut out or faucet cut out needs to be modified. This is what our granite install guys would do. For faucets they would find the largest diamond holesaw they had and do this. Lay a couple of grout sponges soaked in water around the hole or spot to cut the hole. Then they would put a piece of plywood with a hole in it larger then what they needed to drill over the sponges. They would angle the holesaw to start the cut and then plunge down while pressing on the plywood. This would squish the sponges and water would come out cooling the saw and capturing the dust. Keep in mind that as the hole is drilled the water will drip to the inside so plenty of rags were placed there to catch the run off.
Another thing to think about is when you drip coolant on a cutting tool you risk thermal fracture but with a bath will not. Think of pouring hot water on your frozen windshield it will crack everytime. For making a sink cutout larger they used the same process. Use some soaking wet sponges and a straight piece of wood along with your diamond blade saw. Don't let the water get to your power drill or saw unless it is designed for wet use. My two cents, good luck.

[Maurice Ungaro]

So, does this mean any capable circular saw?

Mike

In a word, yes.

[Rob Hermann]

I'll preface this with I have never worked with granite at all but, I have drilled glass which I suspect is similar. When we do holes in glass we use a diamond bit and build a dam around the hole with modelers clay and then pour water into the hole. An assistant can keep pouring if necc and then when you get through you can wipe up the mess easily and no dust at all in the air. It keeps the bit cool and the dust down. Good luck with your project.

[Victor Robinson]

I'll need to trim a granite slab in a bit too and was planning on using the Skil (circ) saw method. So this is very timely - thanks Mike for posting the question.

But what I'm not sure about is to have any water in the equation or not? Water...electric saw not meant for wet use...

[Mike OMelia]

Right. A 120v circular saw is NOT a wet saw. This might be a job for an air saw (and an excuse to get one!)

Mike

[Glen Butler]

I have used power tools that were drenched while while standing in a pool of salt water on a concrete floor with nothing more than a tingle to the finger. No breaker trips no GFI. You will be fine, just get to it.

[Tom Godley]

I had to shorten a granite top for my kitchen after a design change -- they cut the 1.25 inch top with a worm drive saw and a diamond blade. This was a straight cut, they did it outside using a straight edge and a second guy was holding a air gun connected to a compressor to keep the cut clean and keep any buildup from moving the saw. Lots of dust!!

The problem with extending a cutout is getting the cut started on the long side!

[Randy Klein]

I would get a quote from a granite installer to see how much a simple cut would cost you.

[Sam Layton]

Mike, cutting granite is not hard. I cut and installed the granite in my small bathroom, c-photo. After I built the vanity I got an est on the granite. The place wanted $750.00 to fabricate the granite and I had to install. That included $100.00 to cut out for the sink. I found a prefabbed slab 2' X 8' for $280.00. I needed about 21" X 49".

I purchased two diamond blades, one for my skill saw and a 4" blade for my angle grinder. I cut the slab outside with the skill saw. I installed the granite and cut the sink hole inside with my 4" angle grinder. I used my shop vac to catch the dust. It did a good job.

I like Rick's idea with the wet sponge. A 4" diamond blade on an angle grinder is all you need. Just make several passes. A good diamond blade cuts really well.

Sam