| 摘要 |
A friction clutch includes drive and follow members. 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 and follow-side contact surfaces so that the output shaft and end-bit mounting section (5) can rotate together, and a cutoff position where the output shaft and end-bit mounting section are non-rotatable together. A shaft (42) has one end side rotatably supported by a first bearing (31A) and another end side rotatably supported by a second bearing (47A). The shaft supports the drive and follow members so that the drive and follow members are arranged coaxially in the axial direction. The drive and follow members are arranged between the first and second bearings.
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