Cutting granite benchtop

[dspman]

Hi all,

I've just discovered this site and it seems like a great resource! I've just hit an issue with some kitchen renovations. I am replacing my old gas cooktop however the sizes of the new cooktops is slightly different. The new ones are a little shorter and a bit wider. I have a granite benchtop which already has the cutout for the old cooktop. The cutout size for the new one is around 460mm x 880mm. I have done some reading on cutting granite and it seems to be very difficult to do and also messy. Has anyone had experience doing this?

As this is a cutout for the cooktop, it doesn't need to be 100% perfect because the cooktop will cover the cut. Should I attempt to cut it myself or give it to a stone mason? I have had difficulty finding a stone mason to come out and do the work. I own an angle grinder and was told I could cut it with a diamond blade (?) How difficult is it to cut using one of these blades? Is there any chance of cracking/breaking the granite? Also, how messy is it? Will dust fly all over the place? I need to be careful as I don't want to have to repaint the whole kitchen!

Any advice would be appreciated. Its an expensive benchtop so I don't want to go and do something I will later regret

Cheers,
Dave

[bricks]

Yes you can cut it with a diamond blade.

• mark out your hole as small as you can ( tight fit) check and double check if your using the template in the box, they are often not quite good enough IMHO.
• Make cuts perpendicular to the line and up to it, remember to account for the curve of the blade. Cut's spaced about 5mm - 10mm apart. Obviously this will require quite a few. Once you have done all of that use a large screwdriver to snap each little piece away from the bench, it will break quite neatly and sharply at the end of your cut.
• If you need to remove a large section, more than say 50mm wide, then make a deep squre cutout in the middle and then use the perpendicular cut to get the final shape and size.

I takes time

It's easy

Dust is a problem

• If you can tape up the cuboard below the opening with tape and cardboard- use the light stick to prevent damage to the finish. This will stop dust being thrown through there.
• What I have done only once, and it worked to some degree was to tape some clear platic to the bench top- with anough slack for the grinder and your hands to go underneath- like a platic sheild. This made the process alot more difficult, but kept the dust inside the oven cuboard. Then you just vacum that out.

[scooter]

Make sure you use the right type of diamond blade, ie. a "turbo" one for dry cutting granite.

[dspman]

Bricks and scooter, thank you very much for the help!!

Bricks, regarding the technique you mention i.e. cutting little slots perpendicular to the line then chiseling them out with a screw driver, is this the best method to use? I am assuming you chisel the cuts out perpendicular to the slots, so along the line? It does seem like it would be time consuming. To cut the dimensions I need, we are talking about 250-500 slots (if my numbers are correct!). Is there any chance of cracking the granite doing this?

I was thinking of just cutting the box out with a straight line. Would this not work or is it too difficult this way?

I should mention that it is black granite and about 2 or 2.5cm thick.

Could you explain this point further:

• If you need to remove a large section, more than say 50mm wide, then make a deep squre cutout in the middle and then use the perpendicular cut to get the final shape and size.

Sorry, I don't quite follow what you mean here.

Thank you once again.

[pharmaboy2]

I've never used bricks method, but i've cut ceaserstone with a simple diamond blade on a grinder, simply along the line of the cut. I've always used adouble insulated grinder, and had a hose running very VERY slowly right at the edge of the cut, to stop the heat getting into the blade. However if you are doing inside a fully fucntioning house, it might be just as well advised to do as bricks says and tape up with plastic and just cut for 5 minutes at a time -= allows the blade to cool
- working under plastic, my guess is 5 minutes is all you could stand at a time!

Most perfect method is probably a small wet saw - just like a circular saw only with a hose attachment - ie hire one - then pull out all the drawers, put4 or 5 towels down, then put a tray in directly under the cut to catch 90#% of the water - again make sure you trape everything up.

the advantage of the wet saw is it produces way way less dust, but more mess - i find wet sludge easier to clean up than fine dust 3 closed doors away! ;D

[journeyman Mick]

I've seen tilers cutting granite and marble tiles using a diamond blade (full rim, not segmented or turbo) and holding a wet sponge against the blade for cooling, lubrication and dust suppression.

Mick

[manoftalent]

If you can take the top off and take it outside ....it would be better, but most can be cut as is, just remember to let the tool do the job, just a firm steady cut ...in two or three goes along the line .....wont cause to much heat in the blade as trying to do it in one go .....wear eye protection and dust mask ...

[arms]

How difficult is it to cut using one of these blades? Is there any chance of cracking/breaking the granite? Also, how messy is it? Will dust fly all over the place? I need to be careful as I don't want to have to repaint the whole kitchen!

Any advice would be appreciated. Its an expensive benchtop so I don't want to go and do something I will later regret

Cheers,
Dave

we just use a 5 inch angle grinder and have a second person holding the hose from a portable dust extractor near the blade and the operator cutting the stone so that the dust goes towards the nozzle ,the only things that escape are larger chips that can be easily broomed up later ,slow and easy is the answer for grinding ,a little at a time with a steady hand

[dspman]

Thanks all for the feedback. It all sounding like too much work hehe. I might consider just getting a stone mason to come out and do the cut for me. I am worried that I stuff it up somehow and crack the benchtop.

Does anyone know any mobile stone masons in Melbourne, preferably around the western suburbs? Any idea on how much they would charge for such a cut?

Cheers,
Dave

[Metung]

That solves the "wider" but what about the "shorter" ?. If the wider is no more than shorter then I would suggest grinding off the edge rather than cutting. I've done lots of grinding on polished granite tiles with those cheap Sontak turbo blades and they really did the job.