Rotary cutting tool and cutting insert

摘要

An insert-exchangeable, rotary tool to which throwaway inserts are detachably attached, the insert (1) comprising substantially square-shaped face and bottom surface (14,16) and an outward curved flank (15) on each side surface, and having a positive-type shape in which an outward curved edge line formed by the face and the flank serves as a cutting edge (11); each flank having in a substantially center portion a flat surface portion (12) extending to the bottom surface without contacting with the cutting edge; a major cutting edge (11) formed by the outward curved edge line circularly extending from its lowermost point (7) toward a periphery of the tool when the insert is attached to the insert-exchangeable, rotary tool, such that it has a negative radial rake; and the lowermost point being positioned inward a center of the outward curved major cutting edge.