I am in the process of digging T-post holes in some mighty hard caliche / Limestone rock. How am I doing it - I just bought a Dewalt DW 25551 Rotary Hammer Drill on Ebay to drill T-post holes using a 1 1/2 in diameter Carbide bit. This is an 11 amp drill that will drill using up to 5 inch core bits in concrete. You can find them on Ebay by doing a search for Rotary hammer Drill. Bosch, Hilti, Hitachi, etc are other brand names for these BIG drills. The drill allows me to put posts where I WANT TO vs where the rocks want me to.