Rotary hammers pound the drill bit in and out while it is spinning. However, they use a piston mechanism instead of a special clutch. This causes them to deliver a much more powerful hammer blow. One can drill bigger holes much faster. Rotary hammers have such force, in fact, that the usual masonry bits are no longer adequate. Their smooth shanks would be pounded loose from the tool's chuck in a few seconds. Therefore, they require special bits which can lock into the rotary hammer and continue on spinning while smashing away. Specifically designed for rock, stone, and concrete work, they have the muscle to get the job done!