A turning tool includes a tool body, insert seat and a turning insert. The turning insert has a top surface and an opposite bottom surface, a reference plane between the top and bottom surfaces, and a center axis intersecting the top and bottom surfaces. A circular cutting edge of the insert is concentric in relation to the center axis. The bottom surface includes a set of radial grooves and a set of flat surfaces. The flat surfaces extend in a plane parallel to the reference plane. The insert seat includes a bottom surface and a rear surface. The bottom surface of the insert seat has a first ridge and a support surface, wherein at least one of the flat surfaces of the turning insert is in contact with the support surface. A cross-section of the first ridge is smaller than a corresponding cross section of one of the radial grooves.

A cermet insert includes a first surface, a second surface, a cutting edge, a third surface located opposite to the first surface, and a through hole extending from the first surface to the third surface. An inner wall constituting the through hole has, at least in a center portion, a binder-phase-rich layer having a higher binder phase content than an interior of the base. A thickness T1 of the binder-phase-rich layer at the center portion is larger than a thickness T2 of the binder-phase-rich layer at an end portion. The thickness T1 is 1 μm or more and 20 μm or less, the thickness T2 is 0.2 μm or more and 6 μm or less. The first surface includes a chip breaker. An arithmetic mean roughness Ra of the chip breaker is 0.05 μm or less when a cut-off value is 0.08 mm.

A turning tool includes a tool body, insert seat and a turning insert. The turning insert has a top surface and an opposite bottom surface, a reference plane between the top and bottom surfaces, and a center axis intersecting the top and bottom surfaces. A circular cutting edge of the insert is concentric in relation to the center axis. The bottom surface includes a set of radial grooves and a set of flat surfaces. The flat surfaces extend in a plane parallel to the reference plane. The insert seat includes a bottom surface and a rear surface. The bottom surface of the insert seat has a first ridge and a support surface, wherein at least one of the flat surfaces of the turning insert is in contact with the support surface. A cross-section of the first ridge is smaller than a corresponding cross section of one of the radial grooves.

A cermet insert includes a first surface, a second surface, a cutting edge, a third surface located opposite to the first surface, and a through hole extending from the first surface to the third surface. An inner wall constituting the through hole has, at least in a center portion, a binder-phase-rich layer having a higher binder phase content than an interior of the base. A thickness T1 of the binder-phase-rich layer at the center portion is larger than a thickness T2 of the binder-phase-rich layer at an end portion. The thickness T1 is 1 ?m or more and 20 ?m or less, the thickness T2 is 0.2 ?m or more and 6 ?m or less. The first surface includes a chip breaker. An arithmetic mean roughness Ra of the chip breaker is 0.05 ?m or less when a cut-off value is 0.08 mm.