cutting granite countertop slab

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Old 03-14-07, 02:40 AM
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cutting granite countertop slab

Greetings,

I bought a prefabricated granite countertop slab from a friend at a price I couldn't refused. It's 8' long, 3/4" thick, with finished trims at the front and sides. I need instructions (lots) to install the slab. Any tricks and tips to cut 8" off one side of the slab and more importantly, the cutout for a 30" wide sink?

Also any instruction, tricks and tips on preparing the base cabinets for the countertop?

The friend says not necessary to have a full plywood underlay, only need to epoxy 3" wood strips to the underside edges of the countertop, and areas where the countertop will actual sit on the base cabinet top edges. I think the plywood underlay provides a lot more support.

Any comments, advises, tricks, tips would be greatly appreciated.

Instruction, the greater the detail, the better.

Thank you....
 
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Old 03-14-07, 06:22 AM
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Not going to be cheap, but I'd suggest having a pro install this for you - too easy to screw up and ruin the slab DIY.
 
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Old 03-14-07, 11:05 PM
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The first question is, do you need two finished ends or what are called returns? Also many pre-fab granite slabs come with back and or side splashes. Do you have these?

From what you say you have a finished front edge, probably a full bullnose on the prefab's. Also the ends or returns are finished the same. If you are going to butt one end of the counter to a wall then you can go ahead and take off the 8" from the end on the wall side.

If you need both of the finished ends youy best bet for a DIYer would be to use a seam. You can cut the granite in half in the middle of where the sink would be. This would give you 2 small seams, 1 in front and 1 to the rear of the sink cut out. By taking the 8" out from the middle of the slab and creating a seam you will not have a need to re-finish 1 of the ends of the slab and your visible seams will be small.

To cut the granite you will need a diamond blade appropriate for granite for a skill saw and or a grinder, preferably both. You will also need a diamond tip hole saw for the faucet holes if you use an undermount sink. For the holes, I like to mark the location of the hole and use plumbers putty to make a ring around the cut-out area and fill it with water. Then drill the hole and the small pond will keep the bit cool and cutting better.

Mark the location for the sink cut out and you can also drill pilot holes for the saw or plunge cut the granite. A grinder with a diamond blade is very helpful for finer cuts.

A surface mount sink will not require you to polish the lip are of the sink, but if you go undermount you will need to polish the edges. You will also need to buy epoxy and appropriate tint for the seam, if you go this route.

For granite I would prefer a full plywood top.

Also I would just say that you will probably have to buy diamond blades but I would guess that if you got the 8' slab for a steal, they are about $250-$475 around here retail, the cost of a pro-installer, with cuts, will run you much much more than the cost of the slab. A handy DIY type can have very good success with a granite install.
 
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Old 03-15-07, 11:01 PM
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Question cutting granite countertop slab

Shooter, if you live around the Vancouver, Canada area...I have lots of beers and wine.

One side of the countertop will be against the walls, so I will not need to go with the seam-in-the-middle route. To made the job easier, I will be buying a drop-down sink with predrilled holes for the faucets and spray, therefore no need to drill holes into the granite.

As I have never cut granite before, I am quite concern that I might crack the countertop (any advise?). I plan to test cut 4" on the side that is butted against the walls. If that goes well, I will use the piece to test my plunge cut technique (for the sink cutout). Using masking tape along the cutting line might help with slippage? Any advise on finishing the cutout corners without over-cutting using a circular saw?

From checking out the hardware and other hardware stores, there seem to be 3 common types of diamond blades.

1. Smooth diamond blade (like those in tile wet saws)
2. Diamond blades with open slits around 1" apart between cutting part of the blade
3. Diamond blades with little ridges around the side of the blade.

The employees were unable to explain the different purposes of each. Any comments? I am thinking #2. for dry-cutting and vibration??

Thanks for your help, and again, the more info the better...
Pike
 
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Old 03-16-07, 02:40 AM
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Sorry, I live quite a bit away from BC, even though I often fly into Vancouver to head up to Whistler, but not this year.

Before I go into a lengthy how to, you may also consider checking with any stone or granite shops. Some shops are willing to only make the cuts and then you can install the slab on your own. You will need a very accurate template or measurements for them to follow.

Having said that if you choose to do it yourself, you really should have a saw like the worm drive, skill saw or similar.

As for blades the smooth continuous blades are generally for wet cutting and are for more precision cuts. Be sure to specify a blade for cutting granite because it does make a difference. It should be a sintered blade as the material embedding the diamonds and it should be a good quality blade. The Turbo blades will be what you want for the dry cutting but they have more potential to chip the granite easier so a steady hand and light but even pressure is required. Also your cuts should be done in multiple passes, making 1/4" or so depth cuts at a time. Allow the blade to free spin and cool often. Also a spray bottle will help with the dust and lightly cool the blade. I have actually heard of guys running water with a hose over the surface of the granite but I am not necessarily suggesting that because of the saw.

If you can get 1" styrofoam to use as under the granite when you cut it will help reduce the chance of the slab cracking on final cuts. To help insure a straight line you can get a straight edge and clamp it to the slab as a guide for the saw.

I asked about backsplashes because a granite backsplash or tile backsplash or any backsplash with a bit of a profile will cover gaps for out of plumb walls or any small cutting boo boo's. If you are not using a backsplash be sure to measure you slab for a correct fit. I would probably make a template out of thin wood, like luan or cardboard and then transfer the design onto the slab.

Also as mentioned I would use 3/4" plywood and then use silver dollar sized dollops of 100% silicone every 6"-8" to hold down the slab.

Your pluge cuts for the sink will also need to be done in 1/4" or so depths also. A bonus is the drop in sink, because your cuts will not have to be as nice and will not need to be polished. Just do your layout accurate. As mentioned a 4" grinder with a cupped blade will help with finishing edges or making smaller radius cuts.

You can make a practice cut but I would not chop off the entire 4" as you will be chewing up the blade. Maybe make a pass or two and if you feel comfortable leave it at that.

Hope this helps.
 
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Old 03-16-07, 08:11 AM
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As for the corners of the sink cutout, a hole saw in the right size will make this work slick, do the four corners first, then cut between them. The same thing works for laminate countertops. Of course for laminate, you don't need a diamond hole saw! I like the idea of building a pond with plumber's putty for the hole saw.
 
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Old 03-19-07, 04:01 PM
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How to DVDs

The advice above is good advice. If you're looking for an actual visual How-To though we carry a DVD set on this exact type of work.

Please visit http://www.defusco.com . We are the only company in the world with these How to DVDs. We are currently in the midst of shooting them all in HD too.
 
 

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