How gears work. Gears are produced in a wide range of sizes, and they vary greatly in use. They range from the tiny gears that drive the hands of a watch to the huge gears that turn the propeller of a supertanker. A simple gear consists of a metal wheel or disk with slots called teeth around the edge.
Gears always work in pairs.
Each gear has a metal axle in its center. The axle of one gear is connected to a power source, such as an electric motor. When the power axle turns, its gear turns and causes the second gear to rotate in the opposite direction. This action powers the axle of the second gear to do useful work. Most gears are made of steel, but such materials as bronze, or nylon or other plastics are also used.