TABLE OF CONTENTS Gears are used to transmit mechanical power; they provide positive transmission of power from one rotating shaft to another and determine speed, direction of rotation, and torque or turning effort. Gears are efficient and dependable. They are used for heavy duty as well as light duty applications and for low-speed drives as well as high-speed drives. Gears are generally made of steel and hardened to reduce wear, but can also be made of cast iron, brass, bronze, other metals, and gears can also be made of laminated phenolic and several types of plastic. Gears are generally made to industry standards established by the American Gear Manufacturers Association (AGMA). Standard gears are available as catalog items from many manufacturers. Machines that require gears are generally designed to use standard gears. If this is not practical, special gears must be designed. The designs of some gears are very complex. Three different types of gears spur, bevel, and worm will be reviewed. The way gears are shown on prints and gear terminology will be defined. This information will provide the basis for a better understanding for reading gear drawings.
There are many different types of gears, Fig. 10-1. The most commonly used type is the spur gear. Bevel gears and worm gears are also popular. Each type of gear has different and specific functions. There are also many modifications to basic gears, such as spiral bevel and double-enveloping worm gears.
