| 摘要 |
Apparatus for rotating a cylindrical workpiece to be machined, having one or two automatic clamping devices on a rotatable hollow driven shaft into which the workpiece is inserted. Each clamping device has three chuck jaws mounted to swing into clamping engagement with the workpiece. Two pivots are provided for each jaw which swings about one or the other of them depending on the direction of rotation: the provision of two pivots gives a smaller and less cumbersome apparatus. To make the pivots swing into clamping engagement, a floating drag plate is freely rotatable on the shaft adjacent the clamping device. It is braked, to restrain rotation with the clamping device but it is positively linked to each jaw by a gudgeon pin, so that on rotation of the clamping device the braking restraint on the floating drag plate is transmitted to the jaws and urges them into clamping engagement with the workpiece.
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