Worm shaft manufacturing type Precursor dies

摘要

According to the present invention, a set of roll-type dies allows a round bar-shaped material to enter the same and machines a toothed gear on an outer circumferential surface of the round bar-shaped material to machine a worm shaft by forming the toothed gear on the outer circumferential surface. The outer circumferential surface of the round bar-shaped material is machined into the worm shaft by an entry portion tooth form area to guide entry of the round bar-shaped material by the set of roll-type dies, and an escape portion tooth form area where an area machined into the worm shaft is discharged through a balance portion tooth form area to continuously machine a tooth form on the outer circumferential surface of the round bar-shaped material while passing through the entry portion tooth form area. The length of the entry portion tooth form area, the length of the balance portion tooth form area, and the length of the escape portion tooth form area sequentially become shorter. The toothed gear can be machined by continuous forward transport of the round bar-shaped material while being separated by taking into consideration the diameter of the round bar-shaped material while a fixing property and a movable property of the roll-type dies making up a set are not classified. A length ratio of the entry portion tooth form area into which the round bar-shaped material moves, the balance portion tooth form area for machining the outer circumferential surface of the material, and the escape portion tooth form area to discharge the machined area of the round bar-shaped material is set to 3:2:1 to allow smooth entry of the round bar-shaped material, prevent overload on the roll-type dies, and machine the toothed gear to facilitate machining.