A new chip breaker was investigated experimentally in order to find out a more effective chip breaker than the commercial chip breaker in turning. A circular cylinder of SS 41 was turned with this chip breaker under the dry cutting. Then it was found that this chip breaker is effective for a wide set of cutting condition. Then circular cylinders of the other steels, i. e. SCM 440, S 55 C, SUS 304, SK 5 were further turned with this chip breaker in this paper. It was found that this chip breaker was almost effective to SCM 440, S 55 C, SUS 304, SK 5 under the most of the cutting condition of the depth of cut from 0.1 mm to 3.0 mm and the feed rate from 0.05 mm/rev to 0.51 mm/rev. The chip breaking performance of this chip breaker was kept up to the worn flank width of 0.2 mm. The principal and feed forces of this chip breaker were slightly greater than those of a commercial one, but the thrust force of this chip breaker was less than that of the commercial one. The surface roughness by turning with this chip breaker conforms well to the theoretical one. However, the plastic deformation of the nose corner on the insert occurred under the cutting condition of large depth of cut and high feed rate, especially for SCM 440.