Which principle is used to describe the shape of a gear tooth?

The pressure angle is a fundamental concept in gear design that influences the shape of gear teeth. It refers to the angle at which the force is transmitted between meshing gear teeth. When two gears mesh, the pressure angle helps to define the contour of the tooth profile. Specifically, it determines the curvature of the tooth and thus affects the efficiency, strength, and smoothness of the gear's operation.

Gears designed with different pressure angles will have different tooth shapes, affecting how they engage with one another. A higher pressure angle usually allows for stronger teeth that can handle higher loads but may increase the noise and wear. Conversely, a lower pressure angle typically results in quieter operation but with increased risk of tooth failure under heavy loads.

Understanding pressure angle is crucial in gear design since it affects not only the shape of the gear teeth but also the center distance between gears, the overall size of the gear, and the load distribution across the teeth. Thus, it plays a significant role in ensuring that gears operate efficiently within a mechanical system.