| 摘要 |
PURPOSE:To obtain products with a sufficient dimensional accuracy even if the products are of a hard brittle material by forming the top periphery of a tool body having a for passing through punched piece into a sharp edge and increasing the thickness of the tool body from the top periphery toward the tool body base. CONSTITUTION:The top of the tool having a straight hole 1 where a punched piece passes through at the center of the tool in the axial direction of the tool is formed into a sharp edge 2 and the thickness of the tool body increases from the sharp edge 2 toward the base of the tool body 3. When a material to be worked is put on the top of the tool body 3 and the material is pressed by a mating tool. An action equal to that by formation of a ''''shear part.... at the entire periphery is generated because the thickness of the tool body 3 increase from the sharp edge 2 of the top periphery toward the tool body base, so that punching force is reduced and shearing stresses are distributed properly.
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