The tube to be drawn is threaded over the long rod which is anchored in place, and the forged-down small end is pushed through the “die,” very firmly fastened to the bench near its center. The pliers take hold of the forged-down end of the tube with a vise-like grip, and are then hooked into the draw chain. The tube is thus slowly drawn through the hole in the die. As these dies are of very hard material, either hard cast iron or hardened steel with hole a little smaller than outside of the tube, they compress the tube upon the mandrel inside and the thickness of wall is thus regulated, the excess metal being squeezed out so that the tube is very materially lengthened. Tallow or grease with the lime-coat lubricate the tube, a little being continually drawn into and through the somewhat funnel-shaped die. As was the case with the “cold finishing” of plate and the drawing of wire, this cold working increases the elastic limit and tensile strength of the steel. So cold-finished tubes are stronger than hot-finished. For many purposes such increase in strength is highly desirable. The exterior of the tube is also made very smooth and uniform in diameter by the drawing. [Illustration: HOW TUBES ARE DRAWN ] The cold-drawing has a disadvantage, however. It somewhat embrittles the steel, as may be inferred from the increase in strength. This is not a serious matter, however, unless the cold-drawing has been overdone. But for smaller sizes of tubing many drawings have to be resorted to, to reduce the steel to the size required. Sometimes ten or even fifteen passes are required before the tubes reach their final size. In such case the tubes have to be annealed and repickled, limed and dried after each pass or two in order to restore to the steel its ductility. If this were not done the tube would eventually break in the die. The last pass is through an accurate “sizing” die which corrects any variation in inside or outside diameter. As the pulling strain which the steel will stand is limited, too much of a reduction in size in any single pass must not be attempted. As annealing, pickling, drying, etc., have to be done after every pass or two, a considerable period of time elapses between the piercing of the billet and its final pass as a small tube. For economy in handling, tubes cannot be considered or handled singly, but must be treated in quantity, so this period between billet piercing and the final pass may be as much as two weeks, possibly more. The tubes must next be straightened. This is done in cross rolls as has been mentioned under the manufacture of lap-welded pipe, or in various other types of machines. [Illustration: CUPPING AND DRAWING SEAMLESS TUBES FROM PLATES ] Much seamless tubing goes into automobile, bicycle, and various other products for which very high grade and perfect material is desirable. One of the many interesting applications of seamless tubing is its use in very fine sizes for hypodermic needles.