Screw and screw forming tool
AssigneeMiyagawa Kinzoku Kogyo Company Limited
InventorEinosuke Miyagawa
Life of this patent
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Abstract
A screw having a star-shaped socket hole in the top surface of the screw head in the form of two equilateral octagons which are disposed between a regular octagon and a regular square inscribed in the regular octagon and which are placed one upon another in concentric and out-of-phase relation with a phase shift of about 45.degree. so that there are eight convex regions which alternate with eight concave regions. A tool for forming the same is also disclosed.
Claims6
A screw characterized in that the top surface of the screw head is formed with a star-shaped socket hole in the form of two equilateral octagons which are disposed between a regular octagon and a regular square inscribed in said regular octagon and which are placed one upon another in concentric and out-of-phase relation with a phase shift of about 45.degree. so that there are eight convex regions which alternate with eight concave regions.
A screw forming tool characterized in that it comprises a punch whose end surface is formed with a star-shaped projection in the form of two equilaterial octagons which are disposed between a regular octagon and a regular square inscribed in said regular octagon and which are placed one upon another in concentric and out-of-phase relation with a phase shift of about 45.degree. so that there are eight convex regions which alternate with eight concave regions.
Dependencies are inferred from the claim text.