A hammer drill is designed to drill holes in concrete not break it up. Rent a small jack hammer with a pointed bit and spade bit.

Chuck

I agree with Chuck... good advice. However, that being said, I've also used a hammer drill (I carry one on all company trucks) to drill a series of holes and then laid into the concrete floor with a sledgehammer to make a few holes in my days... especially sump pump pits... :)

What exactly are you trying to do?

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Mark