| 摘要 |
PURPOSE:To form plural neighboring holes with high accuracy by adding compressive stress at least more than the yielding point of a material to the neighboring peripheries of the holes for forming ring-shaped concave grooves and performing press stamping. CONSTITUTION:Underholes 12, 13 and 14 are formed on a material plate 11 by a press followed by forming the round holes 15, 16 and 17 having the diameter larger than that of the underholes but the same diameters by the press for reducing the neighboring width W. Next, processing is performed while applying compressive stress at least more than the yielding point of the material 11 so that the ring-shaped concave grooves 15' and 17' may be formed on the peripheries of the round holes 15 and 17 on both sides in the range less than the neighboring width W and a heterodiametered ring-shaped concave groove 16' made of a concave groove, where the regional part on the long side is larger than the regional part of the shorter side, may be formed on the periphery of the central round hole 16 respectively for forming a tubular electrode structure 18. Thereby, shifting of the material on the peripheral part of each round hole can be confined thus making the accuracy of the hole diameter and the flatness of the periphery of the hole highly precise. |
