A reversible cutting insert, comprising: opposing first and second end surfaces interconnected by a continuous peripheral surface, with a median plane located between the first and second end surfaces and intersecting the peripheral surface to form an insert boundary line (Lb), and an insert axis perpendicular to the median plane about which the cutting insert is indexable, the peripheral surface including three side surfaces alternating with three corner surfaces, the side and corner surfaces (26, 28) intersecting both the first and second end surfaces at side and corner edges (32, 34), respectively, with each side edge having a major cutting edge, and each corner edge having a corner and minor cutting edge (38, 40), and each corner surface having two minor relief surfaces, each minor relief surface extending away from its associated minor cutting edge, wherein: each minor cutting edge has a projected minor cutting length (L M), in an end view of the cutting insert along the insert axis, and each minor relief surface has a minor relief width between two lateral boundary points of the minor relief surface contained in a horizontal plane perpendicular to the insert axis, the minor relief width varying with an offset distance (Do) between the horizontal plane and the median plane, characterized in that each projected minor cutting length (L M) is greater than the maximum minor relief width (W MAX) of its associated minor relief surface, and a first imaginary straight line extending perpendicular to the median plane and intersecting any one of the corner cutting edges at any point along its length, passes through the median plane inside the insert boundary line (Lb). opposing first and second end surfaces interconnected by a continuous peripheral surface, with a median plane located between the first and second end surfaces and intersecting the peripheral surface to form an insert boundary line (Lb), and an insert axis perpendicular to the median plane about which the cutting insert is indexable, the peripheral surface including three side surfaces alternating with three corner surfaces, the side and corner surfaces (26, 28) intersecting both the first and second end surfaces at side and corner edges (32, 34), respectively, with each side edge having a major cutting edge, and each corner edge having a corner and minor cutting edge (38, 40), and each corner surface having two minor relief surfaces, each minor relief surface extending away from its associated minor cutting edge, the peripheral surface including three side surfaces alternating with three corner surfaces, the side and corner surfaces (26, 28) intersecting both the first and second end surfaces at side and corner edges (32, 34), respectively, with each side edge having a major cutting edge, and each corner edge having a corner and minor cutting edge (38, 40), and each corner surface having two minor relief surfaces, each minor relief surface extending away from its associated minor cutting edge, wherein: each minor cutting edge has a projected minor cutting length (L M), in an end view of the cutting insert along the insert axis, and each minor relief surface has a minor relief width between two lateral boundary points of the minor relief surface contained in a horizontal plane perpendicular to the insert axis, the minor relief width varying with an offset distance (Do) between the horizontal plane and the median plane, characterized in that each projected minor cutting length (L M) is greater than the maximum minor relief width (W MAX) of its associated minor relief surface, and a first imaginary straight line extending perpendicular to the median plane and intersecting any one of the corner cutting edges at any point along its length, passes through the median plane inside the insert boundary line (Lb). each minor cutting edge has a projected minor cutting length (L M), in an end view of the cutting insert along the insert axis, and each minor relief surface has a minor relief width between two lateral boundary points of the minor relief surface contained in a horizontal plane perpendicular to the insert axis, the minor relief width varying with an offset distance (Do) between the horizontal plane and the median plane, characterized in that each projected minor cutting length (L M) is greater than the maximum minor relief width (W MAX) of its associated minor relief surface, and a first imaginary straight line extending perpendicular to the median plane and intersecting any one of the corner cutting edges at any point along its length, passes through the median plane inside the insert boundary line (Lb).