PURPOSE: To set up the position of key groove of die supporting shaft at the position fitting for the die condition and to accurately arrange the screw thread phase of the die supporting shaft at the contact position of raw material, by previously providing indication line on the tip face corresponding to a pair of thread rolling dies.

CONSTITUTION: The indication line 16 is marked on the axis including section included the center of the key groove 6 on the tip face of a pair of dies 1, 1' and the axis including section A" placed at an angle of Q+ in clockwise rotating direction at the left side round die 1 radiately from the center of the die 1 and the same indication line 16' is marked on the right side die 1'. The block 14 having the indication line 17 at the distance H from the lower tip face 15 to the section A"-B" on the support 3 and the lines 17 and 16' are arranged in a straight line and next, the line 16 is arranged in a straight line rotating the die 1. Hereby, relative position of the keys 6, 6' of both dies support axis, is able to conform to the screw thread rolling die without requiring pitch conforming operation leaving streak on the outer circumference of raw material.