GRIP CHANGING DEVICE FOR WORKPIECE AT LATHE, GRIP- CHANGING MACHINING METHOD AND TWO-SPINDLE OPPOSED LATHE

摘要

PROBLEM TO BE SOLVED: To provide a workpiece grip device that changes the grip of a workpiece between an outer peripheral part and a central part of the workpiece at a lathe. SOLUTION: The workpiece grip device is provided with a chucking claw 4 for gripping the outer periphery of the workpiece; a pull rod 8 provided with a hook 11 advancing and retreating on a spindle axis through the center of a chuck; and a holding member 15 with a noncircular hole 16, held detachably in an axial direction while being regulated in rotation on the spindle axis. The hook and the noncircular hole are provided with such shape as to be able to pass at a prescribed relative angle but to be unable to pass at a different relative angle. The outer periphery of the workpiece is gripped by the chucking claw 4 to machine a center through hole 1, and the pull rod 8 is passed through the center through hole to lock the holding member 15. The pull rod is retreated to hold the workpiece, and the chucking claw 4 is opened to machine the outer periphery.