A cutting insert includes a body having an upper face, a lower face, a plurality of planar flank faces, bidirectional acute cutting corners and bidirectional obtuse cutting corners joining two adjacent flank faces. A land has a varying width. An annular island includes a plurality of bulged extensions, relatively longer and narrower chip breaking points proximate the acute cutting corners, and relatively shorter and wider chip breaking points proximate the obtuse cutting corners. A chip breaking ramp surface flanks each of the relatively longer and narrower chip breaking points and each of the relatively shorter and wider chip breaking points. The chip breaking ramp surfaces form a series of non-collinear lines that are at a non-zero angle with respect to the cutting edge.

A cutting tool has an insert holder with an indexable cutting insert removably secured therein. The cutting insert has upper and lower end surfaces with a peripheral side surface and a through bore extending therebetween, and a plurality of upper cutting edges formed on an upper peripheral edge. The peripheral side surface includes a non-circular upper relief surface adjacent the upper peripheral edge and a circular upper abutment surface spaced apart from the upper peripheral edge. Each upper cutting edge exhibits mirror symmetry about a bisector plane, and is non-linear in a side view. The through bore has an inner undercut formed by upper and lower bore surfaces located on opposite sides of a median plane, and a clamping member makes contact with one of the upper and lower bore surfaces at an inner contact zone located between the median plane and a seat surface of the insert holder.

A cutting tool has an insert holder with an indexable cutting insert removably secured therein. The cutting insert has upper and lower end surfaces with a peripheral side surface and a through bore extending therebetween, and a plurality of upper cutting edges formed on an upper peripheral edge. The peripheral side surface includes a non-circular upper relief surface adjacent the upper peripheral edge and a circular upper abutment surface spaced apart from the upper peripheral edge. Each upper cutting edge exhibits mirror symmetry about a bisector plane, and is non-linear in a side view. The through bore has an inner undercut formed by upper and lower bore surfaces located on opposite sides of a median plane, and a clamping member makes contact with one of the upper and lower bore surfaces at an inner contact zone located between the median plane and a seat surface of the insert holder.

A cutting insert has top and bottom surfaces opposing each other and a side surface connecting them. A part of an intersecting ridge between the top and side surfaces functions as a cutting edge. On the side surface, a side surface portion adjacent to the intersecting ridge portion opposing the cutting edge intersects the top surface at an acute angle. At least on a part of a bottom surface, an inclined surface gradually approaching the top surface with increasing distance from a side surface portion on a side opposite to a cutting edge is formed. This allows a part of the cutting resistance to act on the side surface portion. As a result, friction resistance between the side surface portion and the side surface of an insert seat becomes larger, thereby suppressing a shifting of the cutting insert when cutting.

A double-sided cutting insert for a drilling tool includes a top side, a bottom side, and at least one side surface interconnecting the top side and the bottom side and forming at least one cutting edge. The top side and the bottom side comprise a different external profile and chip groove geometry and an identical inscribed circle, and each of the top side and the bottom side comprises four indexable cutting edges.