The air hammer is an automatic hammer driven by compressed air. Air hammers, also called pneumatic hammers, are a kind of pneumatic tool. One type of air hammer is the noisy device used to break pavements. They're familiarly known as "jackhammers". Other types of air hammers are used to drive rivets, chip metal, or remove paint and rust.
An air hammer is controlled by means of a trigger. When the operator pulls the trigger, the air enters the air hammer through the handle and drives a piston forward. The piston strikes a hammer or other tool and pounds it against the work surface.
In some air hammers, valves reroute the air after each stroke. This type of air hammer delivers as many as 3,500 long, powerful strokes per minute. In other air hammers the piston acts as its own valve and reroutes the air as it moves. This type of air hammer can deliver 15,000 strokes per minute, but each stroke is shorter and less powerful than in the air hammers equipped with valves.