Rotary hammer vs. hammer drill: What's the difference?

Hitachi just released a pretty sweet looking new rotary hammer, and I thought I'd use the announcement to clear up a common question: Which kind of hammer do I need?

Both are great for breaking through masonry—like when removing a damaged stucco surface—but rotary hammers are the beefier of the pair.

They're the tool to use if you're drilling through hardened concrete, such as a foundation slab. The hammering action happens when a pneumatic piston continually pounds the bit into the work surface.

The spinning bit pulverizes the concrete and its flutes move the broken material up and out of the hole. Because you can disengage the rotation on most rotary hammers, they can be used as either a drill or simply a heavy-duty pneumatic chisel.

A hammer drill, on the other hand, is a vibrator.

Hammer drills, which punch holes through brick masonry or concrete block, are not as aggressive. If you want to drive an anchor into a brick wall, though, a hammer drill is plenty.

As you use a hammer drill, the rattling noise you hear comes from two ridged plates vibrating against one another. Imagine two poker chips pressed firmly together, spinning in opposite directions.

So while each tool has a beats per minute (BPM) rating—this new Hitachi's ranges from 1200 to 2500—the rotary hammer is the one that's truly "beating" as you use it.

But I guess "rattles per minute" just doesn't have the same concrete-crushing connotation.

Anybody busted through some brick lately?

Tell us about it for our "What's in your toolbox" section.