To prevent the occurrence of deflection and chatter in long longitudinal feed work of a projecting quantity by setting a shaft directional rake angle, a radial directional rake angle, an outer peripheral side concave angle and a front side concave angle of a cutter to a specific value.

A cutting edge tip 4 placed on a tip seat 3 is fastened/fixed to a cutter body 1 by fastening force of a fastening screw 5. The cutting edge tip 4 is a positive type tip for imparting a clearance angle to an outer peripheral side surface. A shaft directional rake angle α when installed on the cutter body 1 is set to 11° to 20° to reduce a cutting load. An outer peripheral side concave angle δ is set to 1° to 5° to shorten a contact range with a wall surface of a side surface of a work material. A front side concave angle γ is also set to about 1° to 5° so as not to contact with the whole when a front cutting edge reaches a bottom surface of the work material. A radial directional rake angle β is set in a range of -5° to 5° excellent in chip discharge in a combination with the shaft directional rake angle α of a large angle.