| 摘要 |
PROBLEM TO BE SOLVED: To enhance the probability that, when the bit part of a driver is driven, it runs into the cross grooves of the driving screw, by forming the maximum width of the base part of the end conical part smaller than the minimum width of the central part of the opening end of the cross groove of the driving screw. SOLUTION: The shaft part of a driver is in a noncircular shape, and cross blades 3 are formed in the bit part 2 at its end, and the end conical part 5 whose vertex 4 is pointed is formed at the further end part of the cross blades 3. The angleαformed by the conical surface 6 of the end conical part 5 placing the axial center line P therebetween is made to be 110deg. or less. Further, the maximum width W of the base part of the end conical part 5 is formed so as to be less than the minimum width w (not shown) at the center of the opening end of the cross groove 8 (not shown) of a driving screw. The end conical part 5 of the driver becomes easily being slid into the cross groove 8 of the driving screw, and the probability in running into the cross groove 8 can be enhanced.
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