| 摘要 |
PURPOSE:To lower production cost and improve an outward appearance by a method wherein a concentric small-diameter semicircular projection is formed on one end face of a cylinder, and a ring groove is formed by butting and securely bonding two cylinders at their diametral step parts of small-diameter semicircular projections. CONSTITUTION:A concentric small-diameter ring projection is formed on one end face 1a of a cylindrical molded piece 1. A half of the ring across a diametral step part 2 is thin-walled. A thick-walled semicircular projection 3 and a thin-walled semicircular projection 4 are integrally formed. The peripheral surfaces of the respective projections are curved outward as circular surfaces 3a, 4a. Two cylindrical molded pieces 1 of such a shape are butted and securely bonded to each other at their diametral step parts 2. In this manner, an obtained rod body is provided with a ring groove 5 having a concaved peripheral surface at the center thereof. |
