Assembly, shock absorber, and method for manufacturing assembly

A method for manufacturing an assembly in which a fixing pin is disposed inside a plurality of stacked circular members to arrange and integrate the circular members in an axial direction thereof, comprising:

• a shaft portion insertion step of inserting a shaft portion of the fixing pin into the plurality of circular members, the fixing pin including the shaft portion extending in the axial direction and a flange portion extending radially outward from one end side of the shaft portion;
• and
• an integration step of inserting a non-circular punch into a non-circular recessed portion provided on an end face of the shaft portion on the other end side to rotate the punch, having the maximum diameter larger than the minimum diameter of the non-circular recessed portion,
• plastically deforming an outer circumferential portion of the shaft portion on the other end side to protrude radially outward from an inner circumferential surface of the circular members, and integrating the plurality of circular members with the fixing pin.