Abstract: The present invention relates to a nib for a forming tool of bolt head or nut, wherein a nib 7 to be used for a tool comprises a segment combination nib 2 composed of a plurality of nib segments 1, and a regular polygonal hole 6 is formed at the inside of the nib. Regular polygon is formed also at the outside of the segment combination nib 2, and a bush 3 having the same shape as the nib 2 is fitted thereto so as to reinforce the nib 7. Moreover, stress absorbing hole 9 is formed on edge portion inner circumference of the bush 3 or outer surface of the segment combination nib 2. Since the stress absorbing hole 9 serves to absorb stress concentration applied to the nib segments 1, the nib 7 is not liable to flaw in comparison to prior art and stopping of the machine for exchange of the nib 7 is scarcely needed. Accordingly a forming tool with effect of improving the productivity can be provided.