JOINT STRUCTURE

PURPOSE:To provide a joint structure which prevents dislocation in the axis of a cylinder relative to a pin after joining so as to inhibit water from entering the cylinder by forming a female thread on the inner surface of the cylinder portion of a cap part and a centering portion on the outer surface thereof, and forming the outer surface of the fore-end of cylindrical portion in a tapered shape with its diameter gradually decreasing toward the foremost end. CONSTITUTION:A cap nut 5 seated on one end portion of a cylinder 4 constituted of a cap portion 5a covering the top end of a pin 2, a flange 5b provided in the outside periphery of a lower portion thereof, and directed outward with its under side having a seat surface for seating on a washer 6, and a cylindrical portion 6c projecting from the seat surface. A female thread engaging with a male thread of the pin is formed on the cylinder portion 5c of the cap nut 5 in its inner surface, and a centering part 5d abutting on the inner surface the cylindrical portion 5c is provided on the outer surface thereof is relatively smaller than the inner diameter of the cylinder 4, and its fore-end outer surface has a tapered portion 5e with its diameter gradually decreasing toward the top-end. This enables simple joining of the pin 2 and the cylinder 4 with each other coaxially and the space for joining can be reduced.