]Dale, I've never used a diamond drill. I have used a diamond 10 inch saw to cut rock, and it holds up well,
Yes, done a few suiseki with a friends.
I learned when drilling pots, that the easiest way to keep water on the work is to set the pot in a tub with water just covering the area to be drilled. The pot will stay cool and lubricated. .
Just don't drop the drill in!!
Re. concrete, I think it's best drilled using a carbide tooth core drill in a rotohammer. Maybe a diamond drill is too fine to cut effectivly in concrete which is softer than high fired ceramic. Just a guess.
Possibly the differences in hardness ( concrete, rock substrate, etc,) as you go through the concrete.
Yes, I use carbide drills in a rotohammer to drill the cement cast "wood rounds" or "cypress looking slabs" I use on top my monkey poles. Ziiipppp....right through!
Dale