Hammer Drill vs. Impact Driver
A hammer drill’s body style is similar to that of a drill-driver. However, a hammer drill is built to add extra power and a hammering action. The direction of force is different, though. The force of the hammer drill is applied directly to the bit as it hits the medium as if there was a hammer being smacked into the back of the drill as it presses forward, almost like a jackhammer. This helps break up a harder material with the bit tip while the spirals of the drill bit spin the debris out of the hole you create. Hammer drills are usually used for work with stone and concrete and should be used with masonry bits only.
There are two modes of operation on most hammer drills. In addition to its normal action, the hammer function can be turned off. This lets the drill function as a standard drill-driver for use with wood or metal. This can be useful when you are unsure what the material is you’ll be drilling – if, for example, you are unsure if there is wood or concrete behind a wall – but since a hammer drill is more expensive and heavier than a standard drill, it would not be an advisable tool for lighter household tasks.