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I recently bought an under-counter kegerator and need to have some holes drilled in the granite countertop for the tap. The template and mount has 1.75" hole in the center (to run the beer lines) and then 4 small 3/8 holes around the center hole where bolts are placed to secure the tap down to the kegerator.

I called our granite installer and they want $200+ just to come drill the holes. Looking online, you can get Diamond Core Hole Saw Bits for $40, and smaller diamond bits for the screws for around $10. Obviously this is cheaper, but can a my standard corded Rigid drill (not VBR or hammer) handle this? Wonder what the risks are in chipping the granite? Some people recommended putting a ice cube in the bit to keep it cool and emulate a wet drill. What would be a technique to get the bit started, so it does not move when making its first cut into the stone?

Any other tips?

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It can cut it and usually nicks don't matter since whatever going on top of it are a bit bigger than the hole. Your problem is that your holes are probably relative close to both the sink cut out and the back of the slab. When drilling you are taking the chance of causing a stress fracture in the granite in an already vulnerable area. Even a greater chance of causing an issue when you don't have the right tools. I would like to hear other opinions on this but I am not sure the risk is worth it. Also I am assuming for $200 they take fault if there is a crack. –  DMoore Jul 30 '13 at 18:11
    
Also I would be very careful with those bolts. Overtightening those can cause issues too. I hate paying anyone to do something simple like that at my house but man this could turn out bad. And I have cut through many 1cm granit shower panels - you do not need a hammer drill, bit is key, and I drilled with someone constantly hosing the area with cold water - and would not drill for more than 5-10 seconds at a time. –  DMoore Jul 30 '13 at 18:15
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another option would be to route the lines from under the counter, into the wall, behind the backsplash, then out through the wall, using a wall mounted beer-tap. –  mike Jul 30 '13 at 18:42
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This is one of those things that I say: $200 fee, or $2000 replacement? If you don't care whether you do anything from chipping to cracking your entire countertop, by all means, give it a go. Otherwise, more often then not, you are paying for the "experience" that an expert can provide, not the actual work. But it's a kegerator... you can extend the hose and put the tap just about anywhere you like, including the backsplash as @mike suggests. Or as I say.. who needs a built-in soap or water dispenser, when you can have a built-in beer dispenser. –  Jacob S Jul 30 '13 at 18:55
    
Just to expand on @JacobS's comment: at best you're going to spend a couple hours (maybe more) and maybe save $100 or $150, assuming everything goes well.. This just doesn't seem worth the risk to me when weighed against the cost of complete replacement if you screw up. –  gregmac Jul 30 '13 at 20:37

2 Answers 2

Alignment, temperature, speed. All critical in cutting stone. A drill press or alignment jig would be better than just a handheld drill (and definitely not a hammer drill) and a constant water stream and slow speeds are necessary. At some point you are spending on tools close to what the stoneman wants.

DIY is possible, but this is the kind of job I would pass on and call in the pros.

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I agree, it's more about tools than time. –  GdD Jul 30 '13 at 18:32
    
If you're going to DIY, I'd also recommend getting a scrap piece of granite of equal thickness for practice and testing your bit works. Presumably somewhere that sells countertops will give/sell you scrap, though I have no experience with this. –  gregmac Jul 30 '13 at 20:34
    
By alignment jig, you mean some other material with the holes pre-drilled in it that I would clamp to the countertop? –  mohlsen Jul 31 '13 at 11:35
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There are several tools to hold a handheld drill in perpendicular alignment, similar to (but not as sure as) a drill press. –  bib Jul 31 '13 at 12:26
    
I'd drill the 3/8" holes without qualms, maybe even with a handheld, but that 1.75 incher is just begging to jam a hole saw and swing whatever alignment jig you've made around until it goes flying across the room. If you really want to do this, drill some practice holes in scrap first. –  Wayfaring Stranger Nov 19 at 14:07

Having DIY'd a granite tile (24"x24") benchtop with undermount sink I'd say it's not that hard if you're careful and patient. As the comments above say you absolutely must use an alignment jig or similar. I had the freedom to use a drill press and I put masking tape on the stone to give a safe surface to get the last 1mm of alignment.

You probably need to press quite hard to cut the stone, the main cause of overheating is rotational speed You must use the lowest drill speed the drill will allow. With a drill press this would be less than 250RPM, handhelds rarely go this low.

For a hole around 2" it can be convenient to get one of the hole saws with a center bit and predrill an alignment hole with a 1/4" bit. The holesaw will try to wander when you first press it against the surface. Counter-intuitively applying more pressure (lots more) rather than less for the first 1/16 will get you a cleaner start with a handheld drill. Otherwise it can push with considerable force. If using a jig you must clamp it down firmly.

If you can't clamp the jig in place I think you should get the same effect by gluing it to the benchtop. Use a water soluble glue and test it by trying to knock it loose with a mallet. I haven't tried this but in principle it should be equally effective.

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