| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for forming a deep hole, in which deviation from the axial center and variance in the hole diameter, are small even in the case the L/D ratio is≥10. SOLUTION: A base stock W is set on a guide 4 in a die 1 and the base stock is extruded with a punch 6 from the upper part. Then, the deep hole is formed with a perforating pin 3 in the axial direction of a cross sectional area reduction part W1 formed by forward extrusion. As a condition of the forward extrusion, a tensile-stress region is present in the inner part of the base stock if a die half-angleαis≥30°and a cross sectional area reducing ratio is≤25%. And, since the load applied to the perforating pin 3 is reduced with the tensile stress if the hole is formed on this condition, the deep hole having small deviation from the axial center and small variance in the hole diameters in each depth can be obtained. COPYRIGHT: (C)2008,JPO&INPIT
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