THREAD ROLLING MACHINE TO PREVENT BENDING OF AXIS OF WORK

PURPOSE: To dispense with the work to straighten the bending of the axis after the thread rolling by providing a bending preventing means to prevent the bending of the axis of a work in a thread rolling machine. CONSTITUTION: A work 10 is arranged on a rest 35 between thread rolling cylindrical dies 11, 13. A hydraulic pump 105 is driven to move a piston 91 to the left while rotating devices 19, 21 are rotated in the same direction at the same speed. The thread rolling cylindrical dies 11, 13 presses a work 10 to start the thread rolling. After a prescribed period of time is elapsed, a controller 39 is controlled so as to reduce the moving speed of the thread rolling cylindrical dies 11, 13. During the finishing process, plain cylindrical dies 23, 25, 27, 29 are brought into full contact with a shaft part of the work 10 at the prescribed time, and the pressing is achieved. The bending of the axis of the work 10 is straightened by this pressure. A direction switching valve 101 is switched to (c) at the prescribed time, and an opening/closing valve 103 is opened. The high pressure in a cylinder 93 flows from a hydraulic pressure port 99 to an oil tank 117, and the piston 91 is moved by a spring 97 to the right.