To provide a molded part including a hole which prevents the easy production of a useless circular arc part at a point for connecting the inside surface of the hole and the surface of a base material and a burring method of forming the hole.
In the molded part including a stretch flange and the hole consisting of a base, the stretch flange piercing the base and stretching to a surface from one surface of the base to a surface on an opposite side is formed in the hole. The ratio of a radius of the circular arc part where the inner surface of the hole and the surface of the base are connected to the thickness of the base is smaller than 0.4. Alternatively, the ratio can be made smaller than 0.2. The burring method of the molded part including the hole includes a step of providing a punch having a non-circular columnar shape in a head part, a step of forming a prepared hole in the base material, and a step of forming the stretch flange in the prepared hole.
LIN CHENG-HUNG
HU ZHI-GANG
ZENG YONG
YANG ZHI-GUO
WANG MING-GANG
HON HAI PREC IND CO LTD
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Takashi Watanabe
Yasuhiko Murayama
Shinya Mitsuhiro