| 摘要 |
PROBLEM TO BE SOLVED: To provide a bit coming-off preventing mechanism for a power tool by surely preventing switching by mistake from a fixed condition to an opened condition so as to improve reliability. SOLUTION: A bit coming-off preventing mechanism is provided with a roller 2, arranged capable of protruding/sinking in a roller hole 1a formed in a cylindrical drill holder 1 to penetrate in a radial direction thereof, to engage with a recessed part of a bit 11 inserted in the drill holder 1 in a condition protruded to an internal peripheral surface side of the drill holder 1, to hold the bit 11 incapable of rotating relating to the drill holder 1, and a sleeve S assembled outside the drill holder 1 coaxial thereto and rotatable in a peripheral direction to protrude/sink the roller 2 in accordance with its rotational position in the roller hole 1a. The sleeve S is arranged slidably in an axial direction relating to the drill holder 1. A lock means L impeding rotation in the peripheral direction of the sleeve S relating to the drill holder 1, in a condition that the sleeve S is slid in one side, is provided.
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