A boring or drilling tool, in particular for metallic materials, having
- an essentially cylindrical tool body (1) defining a longitudinal axis (16), which tool body (1), on a fastening end, has a coaxial fastening shank (2) and an opposite end, said opposite end defining a cutting-edge end;
- at least one cutting element seat (10, 11) for receiving said at least one cutting element (7, 8) located at said cutting-edge end (4);
- at least one flute-like chip removal space or recess (14, 15) formed on an outer circumference of the tool body (1),
- said chip removal space or recess being open on said cutting edge end (4) of the tool body (1) in an end face (17) thereof, and extending over the length of the tool body into the region of its fastening end, and
- said at least one seat (10, 11) for receiving said at least one cutting element (7, 8) being formed in the region of the chip removal space or recess (14, 15) on the cutting edge end (4) of the tool body;
- wherein said at least one cutting element (7, 8) is secured to the at least one seat (10, 11) and has at least one cutting edge operative on said end face (17) of the tool body (1);
- wherein said at least one cutting element (7, 8) protrudes radially with an outer cutting edge corner (7b) adjoining said at least one cutting edge (7a, 7b), beyond the circumference of the tool body (1),
- said outer cutting corner (7b) defining, in operation of the tool, a flight circle,
- whereby in material removing machining, cutting forces act on said at least one cutting edge (7a) at said end face of the tool body (1) and to generate a resultant radial force (F) which is radially oriented with respect to said longitudinal axis (16) and located at an angular position relative to said at least one cutting element;
- said tool further comprising
- means for improving the rigidity of the tool body (1) and for counteracting elastic bending under the influence of said resultant radial force (F),
- said means including
- the shape of the at least one chip removal space or recess (14, 15) in the tool body,
- wherein each chip removal space or recess (14, 15) is divided into three axially adjacent segments (I, II, III);
- a first segment (1) adjoining said end face (17) of the drill body and including the at least one cutting element seat (10, 11), and extending in axial direction at least slightly beyond the axial length of the at least one cutting element from the cutting end (4);
- a second segment (II) axially adjoining said first segment and being formed, helically, with a twist (21) of less than 90.degree. relative to said longitudinal axis (16) of the tool body,
- said third segment (III) axially adjoining said second segment and being formed essentially straight-fluted and oriented at least substantially parallel to said longitudinal axis;
- and
- wherein the axial length and twist in said second segment (II) is dimensioned such that the primary axis of inertia (0-0) of the geometrical moment of inertia in a cross-section where the second segment (II) adjoins the third segment (III), at least approximately corresponds to the angular position of the resultant radial force (F).