Abstract: A helical cutting tool having a plurality of cutting inserts of quadrilateral configuration removably attached to seats formed in the cutting tool, with each insert including a cutting edge extending in the axial direction bounded on opposite sides by a pair of parallel, radially-extending edges. The cutting inserts are disposed in a helical array in which the cutting edge of each insert is spaced in the circumferential direction from the seat of the next adjacent insert and is in overlapping relationship in the axial direction with the cutting edge of the next adjacent insert, and in which the radially-extending edges of each insert are in overlapping relation with the radially-extending edges of the adjacent inserts, such that the cutting edges of all the inserts define a continuous, non-interrupted, cutting line of stepped configuration.