| 摘要 |
PURPOSE:To easily work a long sharp part at low cost by forming a circular columnar part sharply after forming the taper part diminishing the tip part of a pin blank and the columnar part having a short smaller diameter continuing thereto. CONSTITUTION:The tip part of a columnar pin blank 20 is subjected to a drawing by a header to form the taper part 21 becoming gradually slenderer at the tip composed of the curved face having a lenient inclination and smooth and the columnar part 22 having a short smaller diameter continuing to this taper part 21. At this time the boundary zone 23 of the taper part 21 receiving the largest resistance at the pin driving time and the linear part of the pin blank 20 becomes the smooth continuous face having a lenient inclination. The columnar part 22 is then formed sharply by cutting to form the comparatively long sharp part 25 composed of a formed tip part 24 and the taper part 21. The length of the sharp part 25 is taken as 1.5D<=L<=2.0D (wherein D is diameter of pin blank).
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