| 摘要 |
PROBLEM TO BE SOLVED: To provide a collet chuck device of an automatic lathe capable of reducing the wear and noise of a bearing member without causing-an increase in cost and the complication and enlargement of a structure. SOLUTION: In the collet chuck device, the outer peripheral section 31 of a shifter 21 includes a tapered portion 32 and a large diameter portion 33 and a control unit portion controls the driving torque of a servo motor 47 to a first driving torque enabling the shifter 21 to move relative to an actuating portion 36 when a collet chuck 13 is to be opened or closed. When the collet chuck 13 is closed and the actuating portion 36 abuts against the large diameter portion 33, the control unit portion controls the driving torque of the servomotor 47 to a second driving torque being smaller than the first driving torque and enabling the shifter 21 to be kept in a state in which it will not move in the direction of the axis of a main spindle 3. Thus, the shifter 21 is pressed with the second driving torque by the servomotor 47 and a single row deep groove radial ball bearing 23 is exerted with a preload derived from the second driving torque.
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