Method and jig for manufacturing butterfly valve

A method for manufacturing a butterfly valve including a valve housing having a fluid passage therein, a valve shaft rotatably provided in the valve housing across the fluid passage, and a valve disc fixed to the valve shaft in the fluid passage, the method comprising:

• providing a pin having a head portion and a shaft portion;
• the valve shaft including a valve-shaft-side through-hole having an axis extending in a direction perpendicular to an axial direction of the valve shaft and through which the shaft portion of the pin is insertable;
• the valve disc including a valve-disc-side through-hole corresponding to the valve-shaft-side through-hole and through which the shaft portion of the pin is insertable;
• attaching the valve disc to the valve shaft such that the valve-shaft-side through-hole and the valve-disc-side through-hole communicate with each other;
• inserting the pin into the valve-shaft-side through-hole and the valve-disc-side through-hole from a side of the shaft portion of the pin;
• when welding a tip portion of the shaft portion of the pin to a periphery, pressing the valve shaft from a side of the head portion of the pin toward a side of the tip portion of the shaft portion of the pin to deform the valve shaft;
• and
• releasing the pressing of the valve shaft after completion of the welding.