Brass with improved machinability, punching and forging, and like other metals with the name of “free cutting”, Pb (lead) is added to the dual alloy of copper and zinc. It can be said that brass is particularly easy to cut because it is relatively easy to process even with a small cutting force and chips are easily separated. However, some cracks occur in hot working due to the inclusion of lead. It is used for watch parts, gears, musical instrument valves, etc.