| 摘要 |
PROBLEM TO BE SOLVED: To provide an appreciably convenient and innovative Phillips screwdriver bit structure. SOLUTION: This bit structure has four prescribed-width blades 2 projecting radially at the tip of a bit rod 1. With a face F1 perpendicular to a center bit axis L of the bit rod 1 being as the border, each of the four blades 2 divides into a first or tip-side blade 2a whose distance to the center bit axis L becomes smaller as it is nearer to the tip, and a second or base-side blade 2b whose distance to the center bit axis L becomes smaller as it is nearer to the tip and whose tip face 2b' exposed overlaps with a radially outside part of the perpendicular face F1. The base of the first blade 2a and the tip of the second blade 2b are different in width, and the side edges of both first and second blades 2a and 2b are practically parallel to each other.
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