| 摘要 |
PROBLEM TO BE SOLVED: To prevent a pile upper end from being bent in a driven head extending direction, by decentering an axial center of a pile upper end from an axial center of the entire pile portion, rounding an intersection angle formed by the upper end and the driven head, and enlarging a cross sectional area of the upper end relative to a cross sectional area of the front end of the pile portion. SOLUTION: A pile portion 4 is formed such that an axial center X of its upper end is decentered from an axial center Y of a section from a central portion to a lower end thereof, in a direction opposite to a direction that extends a driven head 5. In this formation, when an upper edge of the pile portion 4 is driven, a force is sufficiently downward transferred along the axial center Y. An intersection angle Z formed by the pile portion 4 and the driven head 5 is subjected to rounding processing. Thus, even if an upward strong force is applied on the front end of the driven head 5 due to an uplifting force of a roof tile, a fractural shearing force is not applied on the same. Therefore, the head 5 is prevented from being detached from the pile portion 4 due to crack occurring at a base of the head 5. Thus, nail driving work can be efficiently carried out without bending the pile portion in the driven head 5 extending direction, and the strength of the head 5 can be reinforced.
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