On Fri, 04 Sep 2009 15:50:15 +0100 (BST), "Dave Liquorice"
wrote:

Leaning on the drill, particulary with a long bit, is going to make
it flex/bend and deflect off harder bits in the wall rather than
drill through them.

Perhaps that was my mistake then. I don't remember consciously leaning
on the drill but I guess I must have done without realising it.
Perhaps it is an old habit from the old days of pre-sds drills? I
haven't had any trouble before but then again, I haven't done a deep
sds hole before now.

It's probably asking a bit much to get a 15mm pipe through a 16mm
hole as well. As others have pointed out it really ought to be
sleeved. Cement and copper don't get on...

I think I have used 16mm holes in wood and brick to pass pipes through
but for concrete it clearly doesn't work.

I know cement and copper have been discussed on the group before but I
didn't think there was any consensus whether they corroded or not. I
seem to remember people arguing both sides. I was thinking of lining
it more for protection so the copper did not get scratched on the
jagged edges of the concrete.

Our house was built with copper CH pipes buried in the concrete floor.
I thought this was wasteful as it was heating the concrete, not the
radiators. The 30 year old copper pipe was black. Is that a sign of
corrosion? But it certainly was not leaking and it was 30 years old.