| 摘要 |
PURPOSE:To enhance a strength of a ball receiving seat to smoothly rotate a ball for a long term by a method wherein the ball is rotatably held by a tip edge part and inward projected parts formed by pressing and deforming the vicinity of a tip of a metallic pipe inward as the ball receiving seat, and the outer diameter of the ball and the wall thickness of the pipe are determined so as to meet a specific relation. CONSTITUTION:A ball 5 is rotatably held at a tip of a metallic pipe 2 by a plurality of inward projected parts 3 formed by pressing and deforming the vicinity of the tip of the metallic pipe 2 inward as a ball receiving seat and a tip edge part 4 formed by pressing and deforming the tip of the pipe 2 inward. In this ballpoint pen tip, where the outer diameter of the ball is Amm and the wall thickness of the pipe 2 is Tmm, the both are determined so as to meet the relation of A/T<=5.8, pref. 2.5 <=A/T<=5.8. As a result, the ball receiving seat can be enhanced in strength and prevented from cracking, and the ball can be smoothly and stably rotated for a long time. |
