Most real-life gears use teeth that are curved in a certain way. The sides of each tooth are segments of the so-called involute curve. The involute curve is fully defined with a single parameter, the diameter of the base circle from which it emanates. The involute curve is defined parametrically with a pair of simple mathematical equations. The remarkable feature of an involute curve-based gear system is that it keeps the direction of pressure between mating teeth constant. This helps reduce vibration and noise in real-life gear systems.
The following tutorial will show you how to model a perfectly meshing involute gear pair in just a few minutes.
Related: Involute Gear Calculator