Stopping in to say hello, and recommend a couple new bits and rent a small hillti drill with a depth gage, most of the time they come with bit's so buying a couple bits is out and save you plenty. A slab that is over 8 to 12 mouths old will be harder than a rock (Should be) and plenty of rock to bor threw on each hole, we did a test hole on my friends shop a few years back and the drill walked on us even after we made it a 1/4'' in, so we tried a small hillti drill and it kept going strait and drilled the holes neatly for the led keepers.