Safe to drill through stone?


I have a client, who is renovating his house, so as to move in from a rental, and wants some electric jobs (I am an electrician). One of them, is changing the main feed from the electricity meter to the main distribution panel. The old one is probably from the '60s, and is only 6mm^2 (#12aprox) with an allowed amperage of 25 A @ 230 V. I want to install 10 mm^2 (#10) or 35 A max amp. It's gonna be a three-conductor cable, also 3 X 10 mm^2 (live, neutral, earth). Ther problem is, the front side of the house is paved with stone tiles, and I want to be extremely careful when drilling the hole for the cable. I'm gonna use a plain pneumatic drill (1000 W), it goes without saying I'll start with a small bit (5 mm) and gradually change them, until I will use my largest (22 mm). Is there anything I must take care of, so as not to crack the stone? TIA,
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Tzortzakakis Dimitrios
major in electrical engineering
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Which is it - electric or pneumatic? In either case you do NOT want to work your way up through drill bit sizes to cut through the stone tile. That's pretty much guaranteed to crack it. Buy yourself a diamond core bit - a stained glass shop will probably have one, as will most any tile store. Do not drill in hammer mode with a core bit. Have a hose dribble water onto the cut as you're drilling to flush away the slurry and keep the bit and tile cool.
Something like this: http://cgi.ebay.com/3pcs-22mm-7-8-Diamond-coated-core-drill-bit-hole-saw-/180541443803?pt=UK_Home_Garden_PowerTools_SM
You should drill the tile hole a bit oversize, and then switch over to a regular masonry bit in hammer drill mode to drill through the brick/ concrete.
R
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RicodJour wrote:

http://cgi.ebay.com/3pcs-22mm-7-8-Diamond-coated-core-drill-bit-hole-saw-/180541443803?pt=UK_Home_Garden_PowerTools_SM
I was thinking a carbide tip would work well.
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Uno

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wrote:

hammer drill (electric, not pneumatic as I mention in my post-it's called pneumatic in greek, and I got a bit confused), and I phoned my client and he told me he has a sample of the stone which we will attempt to drill with a regular masonry bit, and if we fail I'll go to Praktiker (like the US Home Depot) and see how much a core bit costs, as RicodJour mentions. But I'd like to cut cost as possible, because to get the job I had to offer a low price, and I still have to pay for gas, because the job is far enough from my house. Thanks anyway for both answers.
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Tzortzakakis Dimitrios
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The diamond core bits will be sold in Praktiker's tile department and shouldn't cost more than ten of fifteen bucks. If the margin's that tight, breaking a tile is going to cost you all of your profit and cost you much more time.
R
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wrote:

:The diamond core bits will be sold in Praktiker's tile :department and :shouldn't cost more than ten of fifteen bucks. If the :margin's that :tight, breaking a tile is going to cost you all of your profit :and :cost you much more time.
Thanks for your answer, I went there yesterday amd we tried to drill with my rotary hammer on a sample of the stone, which BTW is very soft and we tried to increase gradually the size of the bits, successfully and then we tried it on the wall, also successfully (I changed to percussion to drill the wall and concrete, it goes without saying we used masonry bits). We installed 3 x10 mm^2 + 1 X 1,5 mm^2 (#18), the extra conductor is for the meter's signal, with a dual metering, when it changes at night to the cheap electricity tarif, do you have that in the USA? (at day you get charged the regular electricity price, but at night is cheaper, to encourage people to use energy hog appliances at night when demand is less, but you have to apply for a special meter.
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Tzortzakakis Dimitrios
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Yep, they do the same thing here - at least where I live.
When you first mentioned stone tile, I was thinking granite which would be the most likely stone tile exterior cladding over here. You said the stone is soft, what exactly is it? If it's something like travertine or marble, and depending on the thickness, I wouldn't have been as concerned about the tile cracking from stepping up through the sizes of masonry drill bits. Glad it worked out for you.
R
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wrote:

:Yep, they do the same thing here - at least where I live.
:When you first mentioned stone tile, I was thinking :granite which :would be the most likely stone tile exterior cladding over :here. You :said the stone is soft, what exactly is it? If it's something :like :travertine or marble, and depending on the thickness, I :wouldn't have :been as concerned about the tile cracking from stepping :up through the :sizes of masonry drill bits. Glad it worked out for you. Granite is used also here, but is very expensive and used rarely. Must be like travertine, its called "porolith" in greek, but I couldn't find the word in any of my dictionaries. It was thin, like 3/8" or less. Marble is also common, eg I've seen in the new building in the campus of our local college (where I studied), but is also quite expensive. At 10/26, when it's St Dimitrius, I'll ask for a set of diamond core bits as a present (in Greece, we not only celebrate our birthday, but also our patron saint's day), and, maybe, a new tool box and a special crimping tool, for RJ45 plugs (the ones used in LAN cables, also at structured cabling).
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Tzortzakakis Dimitrios
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