On Mon, 13 Feb 2006 22:56:14 GMT, "." [email protected] wrote:


one has to wonder why the diamond tipped core drill was invented and
why drilling rigs were invented and why hundreds of enterprising people
have bought drilling rigs and franchises for drilling concrete )

To make money? ;-)

about the only inexpensive solution for the OP is to scribe a circle on
the outside wall, drill a hole in the middle right through the outer and
inner walls to give a reference, repeat the circle scribe on the inside
and then drill series of holes around the scribed circles until the desired
~185mm hole is achieved.

Yes, that is less expensive than the additional offcut of 8 x 2 but
then he has to ensure every hole doesn't run off as it starts or break
into an adjacent hole and that each hole is perpendicular to the wall
by eye (rather than having a jig that gives him a feel that he's
drilling in the right direction?


as for finish, it's only the outermost 2 or 3 mm which has to be perfectly
circular as the render / plaster will do what it's desigend to do: hide the
underlying imperfections

Assuming he wan'ts to tidy up the rendered finish?

from a critical eye which most people don't have.

True ;-)

personally, hire the rig or I'd get someone in. someone who does a job
day in, day out usually produces a better result and there are times when
even the most avid DiYer needs to box a job off by paying someone else
to get the whole project over a time consuming obstacle.

I'd see that particular job as a bit of fun ;-)

The challenge would be if the outside was accessed by trying to stand
on a 45 deg roof .. ;-) Thanks goodness for ladders and scaffold
boards ;-)

All the best ...

T i m