| 摘要 |
PROBLEM TO BE SOLVED: To provide a driver bit constituted so as to sufficiently moderate impact in fastening by a simple machining. SOLUTION: A bottomed hole 6 is drilled in a bit shaft 3 to form a cavity part 3a, so that the impact received in the completion of fastening can be moderated by the cavity part 3a, impact to a driving blade 2 can be reduced, and damage of the driving blade 2 can be prevented. A plurality of bottomed hole 6 are disposed at a plurality of stages, so that a substantially U-shaped cross section can be dispersed over a certain length and the entire periphery of the bit shaft, stress concentration can be avoided in the cavity part 3a, and the damage of the cavity part can be reduced, The driver bit having arbitrary rigidity can be provided by arbitrarily changing the depth of each bottomed hole 6. COPYRIGHT: (C)2004,JPO
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