Pneumatic, << noo MAT ihk, >> tool is a power implement operated by compressed air. Pneumatic tools have various uses. For example, dentists use air-powered drills to remove tooth decay. Automobile mechanics use pneumatic wrenches to tighten nuts and bolts. Construction workers use pneumatic hammers to break up pavement. In addition, the gas turbines in jet engines and the air brakes in heavy trucks and railroad trains are operated by compressed air.
The air for pneumatic tools is supplied by a machine called an air compressor. The compressor squeezes together air molecules, usually to a pressure of about 100 pounds per square inch (690 kilopascals). The air drives the tool in either a reciprocating (back and forth) motion or a rotary (circular) motion.
Reciprocating motion is used in jackhammers, riveting tools, ramming tools, and digging tools. In these tools, compressed air causes a piston to move back and forth inside a cylinder. The piston then pushes against a striking device at the end of the tool. A small jackhammer can deliver from 2,000 to 3,000 blows per minute. In an air brake, the piston applies or releases the brake after receiving a signal from the driver to do so (see Brake (Air brakes) ).
Rotary motion is used in power drills, power wrenches, grinders, and sanders. Such tools have a rotating part called a rotor, which has several blades. The rotor spins as compressed air is forced against each blade in turn. As the rotor spins, it turns a shaft that is connected to a device for drilling, grinding, or other rotary action. Thousands of rotations may occur per minute. The high speed of the rotations causes the high-pitched noise that comes from a dentist’s drill, the turbines in a jet engine, and other rotating pneumatic machinery.
