Patent ID: 6928732

Claim:
A method of manufacturing piping having a respective joining portion at both end portions of a pipe in which a diameter expanding portion is formed at an end portion of a pipe, comprising the steps of: a first step of adjusting the pipe length necessary to form the diameter expanding portion before forming the diameter expanding portion, a second step of absorbing an excessive pipe material which is not allowed to adjust the pipe length when forming the diameter expanding portion, wherein the diameter expanding portion is formed in a predetermined shape by means of adjusting the volume of material at the forming end of the pipe without occurring flashes and underfills (thin portions); said first step including: a step of positioning one end of the pipe by a jig, the pipe being formed in an excessive length capable of absorbing the fluctuation of the pipe length, a step of fixing the pipe by clamping the pipe at a position apart from the one end of the pipe, which is positioned by the jig, in a determined distance defined by a product size by a pipe chuck, and a step of adjusting the pipe length by adjusting a size of an annular protruding portion formed on an outer circumference of the pipe, and said annular protruding portion being formed by pressing the end of the pipe in the fixing side with a punch used for sizing, buckling the pipe and pushing out a portion of the pipe into a relief space previously formed on an end face of said pipe chuck, and said second step including the steps of: a step of inserting the other end portion of the pipe into a connector having a through-hole, the inner diameter of which is expanded, and a step of caulking the other end portion of the pipe with a diameter expanding tool so as to expand the diameter of the other end portion thereof and caulk the other end portion of the pipe to the inner face of said connector, wherein, as a pipe length fluctuation absorbing portion is previously formed in a portion of the inner face of said connector, when a plastic deformation is given to the other end portion of the pipe by said diameter expanding tool so as to form the diameter expanding portion, the excessive pipe material is absorbed by the pipe length fluctuation absorbing portion of said connector and the pipe length is adjusted and automatically conformed to a predetermined length.