PURPOSE: To bend a rimmed material freely by forming plural concave grooves longitudinally on the bottom face of a metallic mold leaving a part, pressing plural edged plates to the side of the metallic mold where no groove is provided using a spring, and making an auxiliary device engaged to the above.

CONSTITUTION: Many concave groove 8 are formed longitudinally on the bottom face of a metallic mold 5 that is fitted to a metallic mold holder 6 of a bender leaving a part. A proper number of edged plates 10 are pressed against the side on which no groove is provided using a spring 11. On the other hand, a transitory positioning plate 20 that is moved transversely by a pusher 21 and a divider 22 that intrudes into the edged plates 10 interlocking with the former are provided on the side of the bender stand corresponding to the edged plates 10. A regular positioning plate 15 moved transversely by a chain 16 and a regular positioning mechanism 14 consisting of a pawl 17 interlocking with the former are in stalled on the opposite side. A grooved rack 18 that is movable vertically and provided with a concave groove 19 of the same pitch with the concave groove 8 on the bottom of the metallic mold is installed under the pawl 17 allowing connection with the pawl 17.