On Tue, 23 Jun 2009 11:36:32 GMT, Cicero
wrote:

On Tue, 23 Jun 2009 01:43:03 -0700, Rory wrote:

Is there a trick to this?

I had to put up a drilled mirror last night. It's metric of course, but
the holes are exactly 1.5" in from each edge, which made measuring the
holes from the centre line difficult.

So I did the first hole (top right hole and put the mirror in place.
Then holding it and checking it was vertical, I marked through the other
holes.
Removed mirror and drilled other holes. I used a 3mm pilot drill to
try
to start the hole in the right place and then 6mm masonry.

Put the plugs in but a couple of the holes are half the hole diameter
out. . Of course, with a drilled mirror, and the washers used,
there's absolutely no margin for error - how on earth are you supposed
to drill holes in masonary with complete accuracy?

=========================================

You can improve success rate by centre punching as if drilling metal, but
it will take longer. Remove a circle of plaster (about 1" diameter - just
enough to see clearly) and mark the hole position on the brick face.
Centre punch the mark using either a proper centre punch or a 6" nail.

I find that this is where the old fashioned Rawdrill comes in handy
and I always start off in plaster with it. Mark up, line up the
Rawdrill with the mark, one hard whack with the hammer to take it
through the plaster, then a couple more whacks to start the hole in
the base. then use a masonry drill to finish off.

Now
using your smallest bit (1/8") drill the hole directly into the brick /
block. Open up the hole to take a plug and fix the mirror to this hole.
Use the same technique (centre punch / drill) to mark each hole in turn
directly into brick. When all holes are correctly drilled put a plug and
screw into each hole (without mirror) and make good the plaster with
Polyfilla.

If this still doesn't work, drill oversize holes and insert solid wooden
plugs to take the screws.