Conversion. Copper and brass processing. Copper tube is made either by extrusion or piercing. In the piercing method, illustrated here, a hot round billet, or solid piece of copper, about fourty-five inches long, is rotated between tapered rolls and forced against a pointed mandrel which pierces the center of the billet. The billet then emerges in the form of a tube about eleven feet long. The Chase Copper and Brass Company, Euclid, Ohio