PURPOSE: To roll a large gear, etc. at high accuracy without enlarging the size of flat dies, by reciprocating flat dies consisting of a central finishing tooth group and a pair of symmetrical chamfering and escape tooth groups on both sides, and narrowing stepwise the distance of two dies.

CONSTITUTION: A finish tooth group B is formed at the center of tooth surface of flat dies and laterally symmetrical chamfering and escape tooth groups are formed on both sides. In forward stroke of the two flat dies 1a, 1b, the distance between reference pitch lines of two dies 1a, 1b is set to a dimension l1. In backward stroke of dies 1a, 1b, a dimension l2 is made smaller than the dimension l1. Accordingly, in forward working, a shallow tooth form of small reduction is formed on the peripheral face of a work 2, and in backward working, a deeper tooth form than forward working is formed. The number of reciprocations of dies 1a, 1b is determined properly according to the degree of difficulty of working of the work 2.