A bevel and hypoid gear cutting tool comprising a disk-shaped cutter head (30; 120) having a plurality of cutting blade mounting slots and a cutting blade positioned in at least one (31; 121) of said cutting blade mounting slots wherein said at least one cutting blade projects from a face of said cutter head, said at least one cutting blade having a length and including shank portion and a cutting end portion wherein said shank portion has a cross-sectional shape defined with respect to a plane oriented perpendicular to said length, wherein said gear cutting tool further comprises: said cutting blade shank cross-section having a circumference wherein more than half of the cross-sectional circumference is circular in shape, the cutting blade shank portion further including at least one flat surface (98; 108, 109; 128) extending along the length of the shank whereby said cross-section further includes at least one straight line portion, characterised in that each of said plurality of cutting blade mounting slots comprises at least four sides with at least one flat surface being seated against at least one of said sides, the clamping of the cutting blade in the cutting blade mounting slot being of positive seating comprising: a clamping-force-side seating of the blade, a first seating against a first slot seating surface (35; 125), and a second seating against a second slot seating surface (36; 126); the first and second seating surfaces belonging to two different sides of said at least four sides of the blade mounting slot; the positive seating further comprising a first contact type being that of a flat surface (98; 108, 109; 128) on said shank seated against a seating surface (35; 35, 36; 125) of the slot, and a second contact type being that of a contacting point (97; 99; 107; 127) at the circular-shaped part of the shank spreading to a contacting area under the clamping force, wherein: the contact type of one of the first seating and the second seating is the first contact type, and the contact type of another of the clamping-force-side seating or the first and second seatings is the second contact type, and the remaining of the three seatings of the positive seating being of either the first or the second contact type. said cutting blade shank cross-section having a circumference wherein more than half of the cross-sectional circumference is circular in shape, the cutting blade shank portion further including at least one flat surface (98; 108, 109; 128) extending along the length of the shank whereby said cross-section further includes at least one straight line portion, characterised in that each of said plurality of cutting blade mounting slots comprises at least four sides with at least one flat surface being seated against at least one of said sides, the clamping of the cutting blade in the cutting blade mounting slot being of positive seating comprising: a clamping-force-side seating of the blade, a first seating against a first slot seating surface (35; 125), and a second seating against a second slot seating surface (36; 126); the first and second seating surfaces belonging to two different sides of said at least four sides of the blade mounting slot; the positive seating further comprising a first contact type being that of a flat surface (98; 108, 109; 128) on said shank seated against a seating surface (35; 35, 36; 125) of the slot, and a second contact type being that of a contacting point (97; 99; 107; 127) at the circular-shaped part of the shank spreading to a contacting area under the clamping force, wherein: the contact type of one of the first seating and the second seating is the first contact type, and the contact type of another of the clamping-force-side seating or the first and second seatings is the second contact type, and the remaining of the three seatings of the positive seating being of either the first or the second contact type. a clamping-force-side seating of the blade, a first seating against a first slot seating surface (35; 125), and a second seating against a second slot seating surface (36; 126); the first and second seating surfaces belonging to two different sides of said at least four sides of the blade mounting slot; the positive seating further comprising a first contact type being that of a flat surface (98; 108, 109; 128) on said shank seated against a seating surface (35; 35, 36; 125) of the slot, and a second contact type being that of a contacting point (97; 99; 107; 127) at the circular-shaped part of the shank spreading to a contacting area under the clamping force, wherein: the contact type of one of the first seating and the second seating is the first contact type, and the contact type of another of the clamping-force-side seating or the first and second seatings is the second contact type, and the remaining of the three seatings of the positive seating being of either the first or the second contact type. the contact type of one of the first seating and the second seating is the first contact type, and the contact type of another of the clamping-force-side seating or the first and second seatings is the second contact type, and the remaining of the three seatings of the positive seating being of either the first or the second contact type.