Systems of Gear Teeth

1. $14/2^\circ$ Composite system
2. $14/2^\circ$ Full depth involute (FDI) system
3. $20^\circ$ Full depth involute (FDI) system
4. $20^\circ$ Stub involute system

The 14/2° composite system is used for general purpose gears. It is stronger but has no interchangeability. The tooth profile of this system has cycloidal curves at the top and bottom and involute curve at the middle portion. The teeth are produced by formed milling cutters or hobs. The tooth profile of the 14/2° full depth involute system was developed for use with gear hobs for spur and helical gears.

The tooth profile of the 20° full depth involute system may be cut by hobs. The increase of the pressure angle from 14 /2° to 20° results in a stronger tooth, because the tooth acting as a beam is wider at the base.

The 20° stub involute system has a strong tooth to take heavy loads.

In the design of a gear drive, the following data is usually given:

1. The power to be transmitted.
2. The speed of the driving gear,
3. The speed of the driven gear or the velocity ratio, and
4. The center distance (Sometimes given due to space restriction)