PURPOSE: To completely eliminate a molding burr generated at the time of molding and to improve the skin touch by forming a spherical projection in the tip of a fixed edge, constituting the spherical projection of two large and small hemispherical parts, and forming the hemispherical part of the slide contact side larger than the hemispherical part of the skin touch side.
CONSTITUTION: A fixed edge 1 is formed by using ceramics powder by an injection sintering engineering method, and in the tip of the fixed edge 1, a spherical projection 3 of a spherical shape is formed. The spherical projection 3 is formed by hemispherical parts 3a, 3b divided into two to the upper and the lower parts in the center part, and the hemispherical part 3a positioned on the slide contact side 4 is made larger than the hemispherical part 3b positioned on the skin touch side. The spherical projection 3 is brought to secondary working by sand blasting, and a burr 6 in the lower end peripheral edge of the hemispherical part 3a and a parting line generated at the time of molding is eliminated. As for the direction for executing the sand blasting, it is executed from the hemispherical part 3b side. By making the hemispherical part 3a larger than the hemispherical part 3b, in the case of executing sand blasting, small particles (sand) come to hit easily against the lower end peripheral edge of the hemispherical part 3a positioned in the upper part in which the burr 6 is formed and the part of the parting line, and the burr 6 is eliminated surely.
YAMAMOTO YOICHI
MATSUMAE TOSHIYUKI
FUBE JIYUUZOU
