What hand tools to make a hole in stone?

[Nick]

Odd request perhaps. I'm having a new clock case made to replace one that has been damaged. It will be made from 20mm thick granite or maybe marble. The front panel of the case is giving problems. This is 190 x 205mm and contains 2 apertures, first is 100mm square and the second is 20mm beneath the first @ 50mm wide x 35 high. Cutting the panel to size and the first aperture are no problem. My stonemasons mechanised tools are too large to make the smaller aperture. He is more used to kitchens/bathrooms/fireplaces etc. He can do it by cutting/shutting/gluing but this would leave unsightly joins on the front of the case, I would prefer not to use this method. Both apertures are filled by glazed metal frames so the finish to the apertures need not be polished, although they have to be quite accurate. I'm wondering about having go at making the smaller hole myself.

I have woodworking experience and some metalwork but no masonry knowledge. As the material is very brittle I imagine conventional chiselling would be a non-runner. An alternative might be removing most waste by drilling and cleaning up with a suitable tool. Anybody know of (1) a suitable tool or (2) any alternatives? Hope the above makes some sense.

Many thanks

Nick.

[andrewpreece]

Am only guessing but does anyone make diamond grit saws ( like the carbide grit coated wire saws used to cut ceramic tiles? You could start the cuts off with a diamond grit grinder wheel of smallish diameter, that would reduce the amount of material ou needed to remove with the grit coated wire-saw.

Andy.

Andy.

[Andy Dingley]

Use an angle grinder to mark out a small recess, slightly larger than the hole. This only needs to be 1mm deep, but it reduces surface spalling when drilling.

Chain drill holes with something like a 5mm SDS bit (it's worth buying an SDS if you don't already have one). Buy good bits, as granite is hard on them.

Once you have the holes drilled, then try drilling diagonally between them, where possible, to remove as much waste as you can. Break out the central core with a chisel, either hand or SDS. The chisel will also be useful for dressing the surfaces smooth enough to allow the clock to be installed.

If you need a smooth edge, a combination of angle grinder (access permitting) and a carbide "tile file" will neaten things up. Blonde shellac hides many sins too - much granite isn't even polished, just varnished.

I suggest practicing on some scrap granite first.

For really neat work, find a stonemason with a wire saw. If it's thin, a Taurus ring saw used for glassworking can also be used to saw granite.

[bigcat]

damaged.

unsightly

method.

accurate.

knowledge.

Its going to be a diferent approach depending on whether its marble or granite. Marble breaks very easily, granite is hard. With marble the main emphasis will be on not breaking the stone.

Might prove useful: angle grinder with TC or diamond grit dremel with cutting discs masonry drills abrasive Grit coated hacksaw and wiresaw Brick acid would eat marble too, but I wouldnt try it without the necessary knowledge, wot i do not possess.

NT