Chemical element that is added to steel to improve its machinability.
Lead is almost insoluble in iron and when added to steels form small globules that cause two effects: embrittlement of steel, so that when it is machined by chip removal, it breaks more easily avoiding blunting and lubrication of the cutting tool, which allows higher machining speeds.
Lead free-cutting steels have a content between 0.15 and 0.35%.