A cutting tool assembly includes a cutting tool and an indexable cutting insert having an insert index axis. The cutting insert includes parallel insert first and second sides connected by an insert peripheral surface that extends peripherally around the cutting insert. At least one clamping hole opens out to one or both of the insert first and second sides, and at least a portion of the clamping hole is in a clamping region of the cutting insert. The insert peripheral surface includes cutting edges that are spaced-apart and extend from the insert first side to the insert second side. Along a width direction, which is perpendicular to the insert first and second sides, each of the cutting edges is wider than the cutting insert, at least at the cutting region of the cutting insert.

A cutting tool has an indexable cutting insert removably secured to a holding portion of an insert holder. The cutting insert has opposing first and second end surfaces with a peripheral side surface extending therebetween and a central mounting portion. The cutting insert has a plurality of cutting portions circumferentially spaced apart about a central axis, each cutting portion having a rake and relief surfaces located on the peripheral side surface. The central mounting portion has a plurality of female type or male type mounting elements having opposing first and second mounting flanks. The plurality of rake surfaces and first mounting flanks face in a first direction about the central axis, the plurality of second mounting flanks face in a second direction about the central axis opposite to the first direction, and each second mounting flank extends further from the central axis than its associated opposing first mounting flank.