On Tue, 2013-08-20 at 23:46 +1200, RussellMc wrote:
> I can make a large enough hole in time with successive 20mm holes. These
> are hard on the bit, the drill and me - quite a suibstantial amount of
> effort required for one hole through.
> I've been thinking about other possible methods that could be achieved at
> modest cost. Any superior ones would be welcome.

Offhand: why are you drilling 20mm holes? That's alot of material to
move.

I regularly use a 3/8" masonry bit for this sort of thing. It's about 12
inches long.

I just drill holes in the shape of a circle. You NEED a hammer drill,
don't even bother thinking about doing it any other way.=20

Discount drills with a hammer drill mode can be had for about $50 where
I live (no reason to get a dedicated hammer only drill if money is an
issue), and it's more then enough for this sort of work (spend more if
you plan to use bigger bits in the future).

Once the holes are drilled usually a few hits with a sledge hammer and
the "plug" falls out. Then it's a little chisel type work to smooth out
the hole, if you feel like doing that (I usually don't).

I can't imagine the job you're describing taking much more then an
hour.=20

TTYL

--=20
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