why use copper to make worm wheel？

Worm wheel and worm shaft are commonly used transmission components in our worm gearbox. We often see that the worm wheel is made of copper, while the worm is made of steel.

Many people might find this strange: copper is more expensive and not as hard as steel, so why do we use copper to make worm wheel?

Actually, this copper is not ordinary brass; it's bronze, usually tin bronze, which is a copper alloy.

What are the advantages of this alloy? It has good wear resistance. Because the transmission surfaces of the worm gear and worm experience friction and significant sliding, if both were made of steel, they would wear out easily. Using copper enhances wear resistance and also provides a self-lubricating effect. Bronze is slightly softer, and after the worm is machined, the two components run together and automatically adapt to a larger, more suitable contact surface, thus increasing their load-bearing capacity.