| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a method and a punch for working a punched hole, which improves fatigue strength and hardly generates the seizure and wear of a punch during working. <P>SOLUTION: In a method of working a hole, after twice punching a prepared hole which is smaller than the diameter of the objective hole of the final shape and similar to the hole in one working stage, the prepared hole is expanded to have the diameter of the objective hole, both of the difference between the radius ra of the punching part A for the prepared hole and the radius rb of the punching part B for the prepared hole of the punch 11 for the prepared hole and the difference between the radius rb of the punching part B for the prepared hole and the radius rd of the punching part D for the objective hole are not more than 0.5 mm; and both heights of the punching part A for the prepared hole and the punching part B for the prepared hole are not less than the sheet thickness of a material to be worked. After the prepared hole is punched by the punching part A for the prepared hole and the prepared hole is punched by the punching part B for the prepared hole, the prepared hole is expanded to have the diameter of the objective hole by using a tapered part C the diameter of which increases to the diameter of the objective hole. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
