ABSTRACT
Gears are used to transmit torque, rotary motion, and power from one shaft to another. There are four principal types of gearing: spur, helical, bevel, and worm gears. The main requirement of gear tooth geometry is the provision that angular ratios are exactly constant. It assumes that the teeth are perfectly formed, perfectly smooth, and absolutely rigid. To obtain conjugate action, most gear profiles are cut to conform to an involute curve. The discussions are limited to toothed wheel gearing of the involute form. Various applications exist where many pairs of gears are in mesh. Such a system is generally called a gear train. Also referred to as the epicyclic trains, planetary gear trains permit some of the gear axes to rotate about one another. Such trains always include a sun gear, an arm, and one or more planet gears. Various methods are employed to manufacture gears. These can be divided into two classes: forming and finishing.
