| 摘要 |
A driver bit and a header punch for manufacture of screws comprising a screw comprising substantially vertical end wall portions of predetermined depth formed on an end edge portion of a bit fitting groove on a screw head, non-planar bottom portions raised from lower edge portions of the vertical end wall portions toward a center of the screw head, inclined groove portions extending from raised portions of the non-planar bottom portions toward a center of a screw neck, a substantially conical-shaped bottom surface formed on a bottom of the groove, the bit fitting groove being adapted to a driver bit, which has a blade adapted to be fitted into the bit fitting groove and has a lower edge portion of the blade adapted to abut against the non-planar bottom portions. In this manner, groove portions of a cross groove on the screw are improved in construction, whereby it is possible to effectively prevent a driver bit from coming out, prevent breakage of screws caused in the prior art, always achieve an appropriate and rapid screw fastening work even when the cross groove of the screw is broken, and to significantly enhance an efficiency in work. <IMAGE> |
