On 11/21/2010 2:52 PM, Rudy wrote:

As I said, I must be hitting aggregate/stone or rebar ^@!#@#!#@1!

Stick a cut nail or other hardened nail in the hole and see what
happens. Like Steve B said, hitting rebar you will hear a ping, that's
a bitch because the concrete around it will dull a metal steel bit. If
it's a stone, there is a chance the cut nail will go in and hold. Hit
it with a 2 or 3 pound hammer. (wear safety goggles, those suckers can
fly) My last house with a poured foundation had stone in it that was
hard as all hell. It's not always easy but you can get a cut nail in
there if it isn't hitting rebar.