In article , Dave Hinz
wrote:

On Mon, 1 May 2006 17:50:31 -0400, Proctologically Violated©®
wrote:

Drilling the hole--6" diam, I think--is doable, as I got rotary hammers, a
bottle of vitamins, etc...
I figgered I would hammer-drill a dozen or so 3/8-1/2 holes thru, and chip
out the webs, to give a reasonably round 6" hole.

Hire someone with a "Core drill" to come in and do it. Pretty much a
big hole saw. Pay the man and you're done.

But I would like to support sed hole, once drilled, to thwart cracks that
might emanate from it, if left unsupported.

Another reason to core it; you get a nice smooth surface with no corners
for cracks to start in.

Is all this a good idea/bad idea? Wife's not crazy about it.

Definately then, hire it out. That way the mess is _their_ fault, not
yours.

Second this idea. I had to have 2 of 100mm holes put thru a 150mm
reinforced concrete water tank for overflow pipes. Got a man with a
core drill in & the job was fast, accurate, relatively clean. Cost me
just over $100 IIRC and worth every cent.

PDW