The leading end portion of a caulking pawl portion formed in the end portion of a pipe main body is formed integrally with the pipe main body through the side surface portion of the caulking pawl portion which has a larger width in the longitudinal direction thereof than the width of the leading end portion in the longitudinal direction thereof. At the same time, the leading end portion of the caulking pawl portion is also formed integrally with the cap side end of the side surface portion of the caulking pawl portion.
In the method and apparatus of making a header pipe, the end faces of the edge portions of a flat plate, which have been respectively cut into a given shape according to a trimming operation, are then respectively face-struck into a linear shape. Also, in the trimming operation, each of the edge portions of the flat plate is cut into a shape having a larger dimension than that of a finally required shape thereof, and the thus produced excess length portions of the edge portions are worked by compressing when a pair of semidivided cylindrical portions are butted against each other. Since a connecting portion situated between the pair of semidivided cylindrical portions is always pressed with a given pressure, the working properties of the connecting portion in the molding operation are prevented from being revived. Further, in the neighborhood of one side edge portion and the other side edge portion, there are formed pressing recessed portions or pressing projecting portions which, when connecting together one side edge portion and the other side edge portion, are used to press against one side edge portion and the other side edge portion in their mutually opposing directions.
