| 摘要 |
A driving section generates rotational driving force and has an output shaft (31) that outputs the rotational driving force. An end-bit mounting section (5) holds an end bit (10) and is rotatable about a rotational axis. A friction clutch is provided between the end-bit mounting section and the driving section. The friction clutch includes a drive member (241) and a follow member (244). The drive member rotates together with the driving section and has a drive-side contact surface. The follow member rotates together with the end-bit mounting section and has a follow-side contact surface contactable with the drive-side contact surface. The friction clutch is movable between a transmission position where frictional force is produced between the drive-side contact surface and the follow-side contact surface so that the output shaft and the end-bit mounting section can rotate together, and a cutoff position where the output shaft and the end-bit mounting section are non-rotatable together.
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