The distance a worm moves forward when making one complete revolution is called?

The term that refers to the distance a worm moves forward when making one complete revolution is known as the "lead." This is a fundamental concept in the operation of worm gears and screws. The lead is crucial because it determines how far the worm will translate axially in one full turn, which is essential for understanding the mechanical advantage and speed reduction provided by the worm gear system.

When considering worm gears, the lead is directly tied to the screw-like nature of the worm. Each complete revolution of the worm translates into linear movement along its axis, and this linear distance is the lead. Understanding lead is important for applications involving precision movement and force transmission, as it impacts both performance and load capacity in mechanical systems.

Other options like pitch refer to the distance between threads or grooves, helix angle is related to the slope of the thread in a screw, and tooth form pertains to the specific shape of the teeth on gears. While these terms are associated with similar mechanical concepts, they do not define the axial travel movement of a worm upon completing a full turn.