To prevent separation of a plug from a through hole of a hollow blade.
A hole closing process for closing, with a plug 21, a through hole 14 on a secondary interim product 60 of a hollow blade is performed. The plug 21 has an outer portion 22o forming a part of an outer peripheral portion of the hollow blade, and an inner portion 22i forming a part of an inner peripheral portion opposed to an internal space 12, and having an outer diameter larger than an outer diameter of the outer portion 22o and an inner diameter of an outer opening portion 15o of the through hole 14. In the hole closing process, the plug 21 is pressed into the through hole 14 in such a manner that the inner portion 22i of the plug 21 is directed to the through hole 14 from an internal space 12 side of the secondary interim product 60, and the plug 21 is joined to the through hole 14 of the secondary interim product 60.
Masatake Shiga
Tadashi Takahashi
Tetsuo Yamazaki
Yasushi Matsunuma