How to cut 3/4" thick kitchen island countertop

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Old 08-10-12, 10:38 AM
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How to cut 3/4" thick kitchen island countertop

I bought a new cooktop that goes in the island in the kitchen. The new one is less than an inch wider than the old, so I need to enlarge the hole in the 3/4" thick granite by taking out an additional 1" x 20". (Granite sits on 3/4" plywood)

A local countertop guy will come out and make the cut for me for $275 but I figure that for less than that, I can buy myself a tool and blade that can do it myself and have the tool forever.

What tool and blade can someone recommend that can do the job?

Thanks.
 
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Old 08-10-12, 11:02 AM
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Assuming the cook top would cover the cut? I would think an angle grinder with a diamond blade would work. It will create massive amounts of dust so you would have to somehow encapsulate the area of work. They may make a cheap no-name wet grinder that would help with dust.

Just be aware....if you don't carefully control it and heavily protect the areas not to be cut......one slip and you'll have a deep gouge that probably can't be repaired.

Don't know whether they make a saw to do it that would be affordable.
 
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Old 08-10-12, 11:28 AM
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I'm not sure I'd take this on, either.

That said, if you do try this yourself, please let us know how it turns out as you definitely have my curiosity piqued.
 
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Old 08-10-12, 11:32 AM
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I think the only way I'd try is to make a template/shield out of plywood with just a slot for the grinder blade to fit though.

The dust is another issue.
 
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Old 08-10-12, 11:32 AM
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Yes, the lip of the cooktop will cover the cut so it doesn't have to be pretty.

Do you think something like a Dremel Saw Max would be able to do the job with a diamond tile cutting blade?
 
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Old 08-10-12, 11:33 AM
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Yeah, I would want some kind of guide; too little margin for error to do this freehand.
 
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Old 08-10-12, 11:35 AM
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Just saw the Dremel question now - I don't think that thing will have enough nuts to get through the granite. If you have one, give it a shot but I wouldn't go buy one for this job.
 
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Old 08-10-12, 11:54 AM
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I doubt the Dremel as well. Maybe the RotoZip with the angle saw attachment? But by the time you buy all you'd need....you're probably close to the countertop guys cost. Sure....you have the tool....but what if you mess up? You'll still have the tool...but you'll be out a countertop.
 
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Old 08-10-12, 12:33 PM
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Depending on how close to the back wall you have to go I'd probably use a circular saw with diamond blade and a guide as suggested. I find the circular saw easier to control and you can set the depth to just past the granite and change to a plywood blade for the plywood. (Accurate cuts depend on minimum force and a diamond blade usually doesn't cut plywood that well.) Use really good double face tape to hold your guide if you can't clamp it to the front and back of the opening.
 
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Old 08-10-12, 01:45 PM
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For a job done right, no fuss, no mess, and although this is a DIY site, $275 would be a welcome amount to have it done. You may even negotiate a little, who knows. I would not do it myself.
 
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Old 08-10-12, 02:22 PM
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In my estimation, Chandler is the person who has responded on this thread who I believe would have the best chance of pulling this job off DIY and he would not do it. I think that's a pretty compelling argument for hiring this one done.

It's a DIY site but occasionally the best choice is hiring a pro.
 
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Old 08-10-12, 03:28 PM
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Maybe if it something cheaper than granite or a rental property.....but I agree...I sure wouldn't attempt it.
 
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Old 08-10-12, 05:33 PM
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I am amazed at the number of people who don't think this is a DIY job.

I'll have to really think about whether I want to take it on.

I called RotoZip customer support and they recommended their RZ-2000 with ZipMate (right angle) and ZipShield (not sure what that is yet) using a XW-Tile1 Tile X-Wheel, having a 3/4" cutting depth - total cost looks like maybe $125 to $150 depending on where I get it.

The lip of the cooktop is 7/8" on each side so I have some room to play (make sloppy cuts)
 
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Old 08-10-12, 05:46 PM
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If you intend to DIY, I'd use a 4 1/2" grinder with a diamond blade, someone to hold a hose and a wet vac. Definitely use a straightedge... I'd probably clamp a large piece of plywood over the counter on each side to protect it and provide the straightedge / cut line. Cover everything in sight in painters plastic. Use just enough water to keep the dust down. Be prepared for lots of cleanup.
 
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Old 08-10-12, 08:44 PM
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Take some pix when you are through, and good luck.
 
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Old 08-12-12, 01:11 PM
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Use the Dremel solution. Trim the plywood substrate from below first. Mark the granite with a Sharpie. Use the little diamond wheel made for the Dremel. Keep the cut wet with water. You only need to score about half the thickness of the granite. Make your 3/4" 'end cuts' as completely as possible. Then use adjustable pliers (Channeloks) to snap off the granite in pieces.
This method keeps dust and mess to a minimum.
Last time I bought the diamond wheel accessory at Home Depot they were about $15. You may go through two of them. I used them to score and scribe some superhard porcelain ceramic material. Worked great!
 
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Old 08-12-12, 06:17 PM
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Did similar thing last year. I went on Ebay and got a mini circular marble saw for about $40 from some Chinese company. It came with a water attachment that didn't work. It came with a diamond blade that did work. Covered the surface with masking tape and clamped a jig to the side for a guide. Had a friend hold a hose with spray attachment. Made 3 passes. I practiced with 4.5" hand grinder but was to scared to use it when it came to doing the money cut. To give you an idea of the amount of dust....pictures throwing chunks of drywall into a moving blender.
 
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Old 11-10-12, 11:59 AM
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I'm the OP on this and I wanted to follow-up.

The project worked like a charm thanks to several of the posts here.

First of all, I ended up getting a wider cooktop so instead of having to cut 1" x 20", I had to cut 3 1/2 inches each side (!) for a total widening of the opening of 7".

I bought a RotoZip ZipSaw with a diamond blade for $89. Basically a mini circular saw that bish80 described. A regular RotoZip (which I had in the basement) was useless. I first bought a refurbished RotoZip with the angle saw attachment that Gunguy45 described. It was useless. Didn't have the power to cut the granite. Fortunately the online retailer took it back in exchange for the new ZipSaw (same price).

Based on warnings from XSleeper and bish80 about the dust, since this was on the kitchen island, I built a double layer of plastic draping (simple painter's plastic) all the way around the island, taped to the ceiling and to the floor, with the openings in the 2 layers NOT overlapping. Just to confirm, when all done, there was a layer of powdered granite on the island remaining granite but not a bit of dust on the outside. I wore eye protection, ear protection and a heavy duty breathing mask with the filters on the sides. It would have been impossible to do without the breathing device.

As Gunguy45 suggested, I made a channel with 2 strips of thin (1/4") plywood for the blade to fit between for the first cuts and I made several passes, each deeper than the last by adjusting the depth guide on the saw. The first few passes were just to made a groove for blade to fit in and then I removed the plywood. The plywood was clamped onto the granite overhangs on each side. I used the plywood for the long cuts but for the 4 - 3 1/2" side cuts, I was able to hold the saw steady enough and just lower the blade for the initial groove. Once the groove is deep enough and the blade has no where to go, the cutting was easier, but the key was several passes.

In the end, the cuts weren't perfectly straight but the lip of the cooktop cover all of my errors. After the granite was cut, I used a reciprocating saw to cut the supporting plywood underneath. I used no water because the ZipSaw diamond blade packaging warned that it wasn't a wet blade. I made the cuts about 90% of the way through and then as senor-mouse suggested, I lightly tapped with a hammer and the pieces broke, even without removing the support plywood underneath the granite first. If I did remove the plywood first, I probably could have gotten away with less than 90% but that wasn't practical.

All in all, the end product looks very professional. This forum gave me ideas, knowledge, and despite some warnings to the contrary, the confidence to proceed. Remember the pro was going to charge $275 for a 1" x 20" cut so after I decided to get the bigger cooktop, the project was more cost effective as a DIY project and it really only cost me the cost of the ZipSaw, painters tape, painters plastic and the blades. I got 2 blades, one for each side in case the first started to get dull and although I switched blades mid-way, the one blade probably could have done the entire job.

Thanks to all!
 
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Old 11-10-12, 12:08 PM
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Nice job! And thanks for posting back... we rarely find out how the advice given actually worked out! Sounds like the best part is you got a new tool out of the deal. LOL
 
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Old 11-10-12, 01:49 PM
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And your trials and successes may help another member so thanks for posting.
 
 

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