I'm trying to drill 1/2" holes in a concrete basement floor in a 70 year old house. I don't think I'm hitting rebar, but not sure. I can't *see* rebar down in the holes, but I can't get much more than an inch in the floor. I've got a pilot bit and a 1/4" bit down a couple inches but I can't get the 1/2" drill in there for the life of me. I've tried 6 different holes in 2 different locations of the basement with no luck. The first time I was near the foundation, so I thought I was hitting rebar. Now I've drilled out near the middle of the floor, but I can't get through there either. I'm using Dewalt carbide hammer drill bits and a Makita 1/2" hammer drill. Is there some trick to this or something I'm doing wrong? I've drill into concrete millions of times, but I can't get into this floor for anything. Any tips? Thanks.

Not sure of your problem but I doubt rebar. I have a D shank Bosch hammer drill and I have drilled any number of holes from 1/8 to to 3/4" without any issue. Make sure you have the dial set to "H" and the bit is all the way in. http://i.ebayimg.com/00/s/Mjg0WDMwMA==/z/D00AAOSwRLZT~xkL/$_35.JPG?set_id=2 (http://www.ebay.com/bhp/bosch-hammer-drill)

Ended up drilling small hole and busting it with a star drill. Rinse and repeat, then finished up with my 1/2" drill. Just took a lot of patience. Yep, the floor was just that hard.

If it happens again, sometimes you can see filings, or a magnet in the hole.
I have also seen very tough concrete, wondered if it was a very hard stone, or just the concrete? Good you got it.