The smooth motion with which worm gears should continuously operate and an acceptable and reliable service life depend not only on the design and quality of manufacture, but on the selection of two entirely different materials that are paired together. The torque that can be transmitted by a worm gear set is always limited by the surface pressure that the materials, from which they were made, can accept without deteriorating.

There are three principal factors that will effect the performance of a set of worm gears in relationship to the materials that were chosen:

(1) WEAR: The material must have...