A replaceable cutting head is adapted for co-axial coupling thereof, along a coupling axis, with a tool shank in a self-clamping fashion. Both the cutting head and the tool shank have a mounting portion comprising a centering section and a positioning section. The centering section is formed with a peripheral centering surface which extends circumferentially with respect to the coupling axis and has a substantially conical shape at least at two portions thereof. The positioning section has at least two peripherally disposed and circumferentially extending and spaced apart positioning surfaces adapted for the provision of an axial support of the cutting head on the tool shank. Each positioning surface is inclined with respect to the coupling axis so that an axial distance therefrom to a broad end of the peripheral centering surface increases in a direction generally corresponding to the direction of cutting forces acting on the cutting edge during a cutting operation. One of the positioning and centering sections is formed with at least two circumferentially spaced apart fixation wings with, respectively, either the positioning surfaces and or the portions of the centering surface belonging thereto.