Model showing by wire hyperboloidal pitch surfaces of skew level wheels.

This is a diagrammatic model of skew-bevel gears. The geometry of some elements of machine design is difficult to explain by drawing and hard to grasp when examining the finished parts. Before the advent of computer graphics this geometry could best be shown by using teaching models such as this example. The model illustrates the hyperboloidal pitch surfaces of skew-bevel gears. That is, gears on axes which are at an angle to one another but do not meet.