| 摘要 |
PURPOSE:To reduce the one side wear and breakage of a die and the working burr of an elliptical hole by working a round hole at the positions of both ends and the center, working a round hole similarly at the center between the worked adjacent round holes and working the elliptical hole by repeating the action working the round hole at the center of the adjacent round holes each other. CONSTITUTION:A round hole 1 and 2, 3 are worked at the position becoming the center and both ends of an elliptical hole by the round type punch with the width of the elliptical hole to be formed as its diameter. The round holes 4 and 5 having the same diameter are formed in the middle of the round holes 2, 3 at both ends and the round hole 1 at the center. The round holes 6, 7, 8, 9 are in succession worked by the same punch at the center between the adjacent round holes to make the designated dimension of the unevenness or step difference of a straight line part becoming a specified value by repeating the action like this in several times. The resistance applied on the blade tip of the round type punch is thus attained to the symmetrical position with respect to the center of the punch and the size thereof becomes equal as well, so the one side wear and breakdown of a die can be prevented and the burr in working can be reduced as well.
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