Gears are mechanical elements which transmit motion by means of successively engaging teeth.
Gears are used to transmit motion from one shaft to another or between a shaft and a slide.
Rotary motion can be transferred from one shaft to another by a pair of plain cylinders or disk 1 and 2 as shown in figure (a) below.
Power transmitted between two shafts is small because there is a possibility of slip. In order to avoid slipping, a number of projections (called teeth) as shown in figure (b) above.
According to the relative positions of their axes they are classified as spur gear, helical gear, and herringbone gear as shown in figure below.
Applications of Gears: