Method for manufacturing a worm shaft for a gearbox and gearbox incorporating same

A method of manufacturing a plurality of worm shafts for use in a family of gearboxes comprising:

• establishing a common center to center distance between the worm shaft and a wheel for the family of gearboxes;
• establishing a first desired axial pitch for a thread of the worm shaft for a first desired gear ratio based on the outer diameter of a worm shaft blank for use with all gear ratios of the family of gearboxes;
• and
• establishing a second desired axial pitch for a thread of the worm shaft for a second desired gear ratio based on the outer diameter of the worm shaft blank for use with all gear ratios of the family of gearboxes.

A plurality of gearboxes, comprising:

• a first gearbox comprising a first worm shaft and a first gear, the first worm shaft and first gear having a first speed gear ratio, the first worm shaft having a first thread having a first axial pitch;
• and
• a second gearbox comprising a second worm shaft and a second gear, the second worm shaft and second gear having a second speed gear ratio, the second worm shaft having a second thread having a second axial pitch,
• wherein the first and second threads have substantially the same outer diameter.