What element is often added to metals to enhance their machinability?

Sulfur is commonly added to metals, particularly to iron and steel, to enhance their machinability. The primary reason for this is that sulfur forms manganese sulfide inclusions within the metal matrix, which act as chip breakers and reduce cutting forces during machining processes. This results in a smoother cutting action, improved surface finish, and reduced tool wear.

While other elements like carbon, silicon, and manganese can influence various properties of metals, they do not have the same specific impact on machinability as sulfur does. Carbon, for instance, primarily affects hardness and strength; silicon is used to improve the oxidation resistance and fluidity in castings; and manganese helps with toughness and hardenability.