Pipe, spool forming die, and pipe manufacturing method

A pipe extending from a first side toward a second side, the pipe comprising:

• a side wall separating an inside and an outside of the pipe;
• and
• a spool that is a part of the side wall formed to be bent so as to protrude from an outer circumferential surface of the pipe and extending to surround the outer circumferential surface,
• the spool comprising:
• a first portion located on the first side;
• and
• a second portion located on the second side,
• wherein there is a clearance between the first portion and the second portion in a top region that comprises an outer circumferential end of the spool, and
• wherein the first portion and the second portion substantially abut each other in a base region located between the top region and a region of the side wall around the spool.