| 摘要 |
PURPOSE:To improve draw-resisting force by forming first and second projected ribs on the outer periphery of a nut so that they extend in the directions allowing them to intersect each other, and forming the second projected ribs lower than the first projected ribs. CONSTITUTION:First right-hand helical projected ribs 2 and second left-hand helical projected ribs 3 are formed on the outer periphery of a metallic or ceramic cylinder. The height of the second projected ribs 3 is then formed lower than that of the first projected ribs 2. After the cylinder is turned clockwise to be screwed into a prepared hole, counterclockwise rotation of the cylinder is blocked by the presence of the second projected ribs 3, and the draw- resisting force can thus be improved. |
