Patent ID: 8776369

Claim:
A through-hole manufacturing method, the method comprising: a hole forming step of forming at least one pair of diametrically opposed through-holes comprising a first and second through-hole each having a same hole diameter in a cylindrical body by a tool piercing from outside of the cylindrical body, substantially orthogonal to a main axis of the cylindrical body, through an outer wall of the cylindrical body to an inner wall of the cylindrical body to form the first through-hole, and then through the inner wall of the cylindrical body to the outer wall of the cylindrical body to form the second through-hole; and a welding step of sealing the first through-hole by forming a sealing member having a same diameter as that of the first through-hole by welding using a welding jig made of a material having better heat conductivity than the cylindrical body, wherein the second through-hole remains, and a machining burr is not formed on the inner wall of the second through-hole in the cylindrical body.