Free-Cutting Brass

(in Russian, automatic brass), leaded brass, a brass alloyed with lead which contains 57 to 75 percent copper, 0.8–3.0 percent lead, and the rest zinc. The addition of lead promotes the formation of short and friable shavings during machining, reduces wear on the cutting tool, and permits parts to be processed rapidly on automatic machines. Free-cutting brass is produced in the form of rods, strips, bars, and sheets from which bolts, nuts, clock parts, and other mass-produced objects are fabricated. The mechanical properties of free-cutting brass depend on composition and state (soft or cold-worked): ultimate strength is 300–600 meganewtons per square meter (30–60 kg/mm²), and the relative elongation is 2.0–50 percent.