ROTARY CUTTING TOOL AND REVERSIBLE CUTTING INSERT HAVING VARIABLE-WIDTH MINOR RELIEF SURFACES THEREFOR

In a rotary cutting tool (52) used for milling operations, a reversible cutting insert (20) is removably secured in a cutting body (54). The cutting insert (20) has two opposing end surfaces (22) interconnected by a continuous peripheral surface (24), which includes three side surfaces (26) alternating with three comer surfaces (28). The side and comer surfaces (26, 28) intersect with both end surfaces (22) at side and comer edges (32, 34), respectively, with each side edge (32) having a major cutting edge (36), and each comer edge (34) having a comer and minor cutting edge (38, 40). Each minor cutting edge (40) has a projected minor cutting length (L M ), in an end view, and each associated minor relief surface (48) has a minor relief width (W) between two lateral boundary points contained in a horizontal plane (PH), varying with an offset distance (D O ) between the horizontal plane (PH) and a median plane (M). Each projected minor cutting length (L M ) is greater than the maximum minor relief width (W MAX ) of its associated minor relief surface (48).