Abstract: A spinning method for forming pipe bodies of varying diameter. In the spinning method, when a necked portion is formed at the end of the pipe material by the spinning method, working rollers are restricted so as to return immediately before the pipe end instead of being allowed to axially move beyond the end of the working object pipe. The amount of diameter reduction at the pipe end is set to be smaller than that of the most diameter reduced portion connecting to the pipe end. A protruding portion of a so-called bellmouth shape is formed at the working end, thereby preventing generation of fractures originating at the working end of the base portion or the welded portion and generation of wrinkles during the spinning process.

Abstract: Provided is a spinning method of reducing a diameter of a work piece pipe body with processing rollers disposed on an outer surface of the work piece pipe body, the processing rollers being configured to be relatively revolved around the work piece pipe body, wherein, when the processing rollers are axially reciprocated while being moved in a radius direction of the work piece pipe body, wherein the diameter reducing process with the processing rollers is performed under a state in which a wound body formed of an elastic sheet-like material is inserted as a core body into the inside of a portion of the work piece pipe body to be subjected to the diameter reducing processing.

Abstract: Provided is a spinning method of reducing a diameter of a work piece pipe body with processing rollers disposed on an outer surface of the work piece pipe body, the processing rollers being configured to be relatively revolved around the work piece pipe body, wherein, when the processing rollers are axially reciprocated while being moved in a radius direction of the work piece pipe body, wherein the diameter reducing process with the processing rollers is performed under a state in which a wound body formed of an elastic sheet-like material is inserted as a core body into the inside of a portion of the work piece pipe body to be subjected to the diameter reducing processing.

Abstract: When the necked portion is formed at the end of the pipe material by the spinning method, working rollers are restricted so as to return immediately before the pipe end instead of being allowed to axially move beyond the end of the working object pipe. The diameter reduction amount of the pipe end is set smaller than that of the most diameter reduced portion connecting to the pipe end. A protruding portion of so-called bellmouth shape is formed at the working end, thereby preventing generation of fractures originated from the working end of the base portion or the welded portion and generation of wrinkles during the spinning.