On Wed, 27 Aug 03 08:45:46 GMT, (dmc) wrote:

Question one: How likely am I to be able to drill a hole in a rock.

UKC ? Chalk should be easy....

I'd go for an igneous rock, like serpentinite, quartzite or granite.
It's harder to dril, but that's the drill's problem, not yours.

The problems with limestone are twofold. Some sedimentaries are very
prone to spalling, especially where the hole breaks through the
surface. They can also be porous enough on the surface that green
algae build up. This can be either good or bad, depending on style.

Slate (metamorphic) works nicely too, although some grades are a
little splintery, especially if already aged outdoors.


I have a decent SDS drill is this likely to just smash the
thing up?

How big a hole ? You can drill small holes (up to 10mm) without too
much trouble, except for the really flakey stones. You can also
chain-drill holes in a ring, then break out the centre. You'll
probably want an angle grinder and flap disks to tidy up, or make a
flat base on a boulder.

Should I be looking for a non-hammer solution (diamond?).

If you want a 40mm hole, go and hire a core drill.


The other thing is that this "rock" had what the seller called "a special
halogen bulb" in the hole so that the water bubbled up over the bulb.

Very likely an LED, if it's a small "bulb". Use a constant voltage
drive, not constant current.

If you use a halogen, then solder to the pins. They're always prone to
corrosion and especially in a damp environment. I don't like these
silicone encapsulations, as I don't trust the waterproofing. I'd use a
test tube almost full of silicone oil. Keep the bulb submerged in oil
and the test tube underwater for cooling, but leave the airspace above
the bulb to allow for expansion.

I suppose one answer to drilling the hole is to make the rock - anyone
got any recipies for half realistic rock mixes? :-)

Try the pond newsgroups and look for "hypertufa" recipes.


If you're making water features, do some reading on traditional
Japanese designs as well. Sadao Hibi's book "Japanese Detail:
Traditional Architecture, Gardens and Interiors" is good, or
Davidson's "Zen Gardens", if you can find them,