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The manufacture of lead pipe by the ordinary method combines, like that of sheet lead, the double process of casting and elongation. Whatever may be the dimensions of the pipe required, it is first cast in the form of a short and extremely thick cylinder, which is afterwards reduced to the proper size by being forcibly drawn, when placed in a mandrel of the exact size of its internal diameter, through a succession of progressively decreasing steel dies. By this process, however, although affording pipes of good quality, with regard to soundness and finish, lengths of from twenty to thirty feet only can be obtained; and, consequently, when very long pieces without a joint are required, recourse must be had to the hydraulic pipe-prcsa shown in our engraving. This machine consists of a common hydraulic press, T, connected with a double force pump, by which water is pumped beneath the piston, B, through the small metallic pipe, ; above the top of the press, and on a level with the floor of the workshop, is supported by the stout iron pillars, P, a heavy casting, containing the cylindrical reservoir, c, for the reception of the metallic lead, and an annular fireplace, F, charged with pit coal, and communicating with a chimney for the escape of the smoke. At the uppor extremity of the cavity, c, is secured a steel die, of the diameter of the outside of the pipe to be made, whilst a mandrel, m, which passes directly through its center, has the same dimensions as the inside of the pipe which is to be produced. To use this apparatus, the piston, B, is brought into the position shown in the cut, and the space, c, filled with molten lead, through the spout, S, which is immediately removed, and the aperture firmly stopped by a stout iron plug, kept in its place by a strong key. The pressure is now established by admitting the water through a valve, beneath the piston, which forces the other extremity, B', accurately fitting the cylindrical cavity, C, gradually upwards, and causes the lead to escape in the form of a perfectly finished tube through the annular space existing between the mandrel and the fixed collar. The pipe, in proportion as it escapes from the press, is coiled around the drum, D, from which it is afterwards removed, and cut into convenient lengths. The pipe made by this machine is of good quality, and may be made of almost any required length. On admitting the pressure above the piston by means of a valve, the plunger again descends to the bottom of the cavity.J. A. Phillips' Treatise Metallurgy.
