This new form of pipe is manufactured from a high grade of sheet iron or sheet steel, varying in thickness from No. 28 to No. 12. Birmingham wire gauge. The sheet metal from the mill is first cut into suitable strips, the width of which varies according to the diameter of the pipe to be manufactured. These single strips are then, by either a riveting or welding machine, formed into continuous strips of any desired lengths. The former method of joining the ends of the strips is usually employed for the lighter gauges of iron and the latter method for the heavier gauges. The above referred to continuous strip is, by means of an automatic feed, forced into the pipe-making machine, and during its transit through the same the rivet holes are punched, the laps or edges of the strip are brought together under heavy pressure, and so held during the process of riveting. The rivets are all set by compression, thereby avoiding the jar and stretch consequent upon the heavy blows needed in hand riveting. At the same time a shoulder is formed on one of the edges for the other edge to set in, by which means an even diameter throughout the whole length of pipe is maintained. In order to render the pipe perfectly watertight when it leaves the machine, there is inserted between the laps before riveting a hydraulic cement, manufactured for that purpose.

Spiral riveted pipe can be furnished of either black, galvanized or asphalted sheet iron or steel, as required. During the process of manufacture the pipe is always in view of the workman, and consequently, should there be any imperfections, they can be easily detected and remedied, an impossibility in case the seam was brazed or welded.

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