1. Materials 

Because worm gears involve high sliding speeds at the contact point, selecting the right materials is critical to minimize friction and prevent "galling" (welding of metals).

• The Worm: Usually made of hardened steel (e.g., Alloy Steel, Carbon Steel). The threads are often ground to a high surface finish to reduce friction. Common materials include 40Cr or 20CrMnTi.

• The Worm Wheel: Typically made of softer, non-ferrous metals, most commonly Bronze (Phosphor Bronze or Aluminum Bronze).

• Why? The softer bronze deforms slightly to conform to the hard steel worm, distributing the load and reducing wear. In low-load applications, high-grade cast iron or plastics (nylon) may be used.

2. Primary Functions 

A. Speed Reduction

B. Torque Multiplication 

C. Self-Locking 

D. Change of Direction