Tubes of lead and brass are cast in short and thick pieces, and then
drawn through holes in a draw-plate, similarly to wire, but having
a rod or “mandril” passed through the length of the tube to keep the
hollow of the right calibre.
Illustration: TUBE DRAWING.
Iron tubing for gas and water pipes, if more than about two inches
in diameter, is cast; but smaller, or “service-pipes,” are made of
wrought iron plate rolled on a mandril, and welded at the edges by
being drawn at a white heat through a draw-plate.