| 摘要 |
PURPOSE:To produce synthetic resin bolts with excellent accuracy at high speed, while using the die for form rolling a metal screw for the purpose of form rolling a synthetic resin bolt by forming the inclined surface of the screw crest of a die into a convex curved surface. CONSTITUTION:The inclined surface of the screw crest of a die is formed into a convex curved surface, and said convex curved surface is preferably made such that the crest-inclined surface is formed into a circular arc-shape in section. The degree of the circular arc is defined by the kind and the property of synthetic resin and the condition at which bolts are manufactured. The best shape of said convex curved surface is affected by the bulging rate of the curved surface and its material. Formula (a/HX100) is equal to the bulgingrate, where H; the height of the crest of the die, a; the maximum bulging size from the inclined surface of a standard screw crest. For instance, for hard vinyl chloride resin, polystyrol resin and acrylonitrile resin, the bulging rate is preferably 3-10%, and for polyamides resin it is preferably 15-20%. Thus the synthetic resin screw may be form-rolled by said die. |
