Drilling tool, in particular reamer

A method for drilling out a predrilled core bore of a work-piece to a nominal diameter, said method comprising:

• inserting a drilling tool into the predrilled core bore with a defined rotary movement and a defined forward feed movement,
• said drilling tool comprising
• a drill body,
• a main blade formed on the drill body, said main blade having a radially outer cutting edge extending along a longitudinal axis of the drill body up to a blade corner arranged at a drill tip of the drilling tool, and
• at least one groove blade arranged so as to precede the blade corner of the main blade in a direction of rotation of the drilling tool,
• said groove blade having a front cutting edge at the drill tip for generating said groove, said front cutting edge extending transverse to the longitudinal axis of the drill body and transitioning at the blade corner into a groove-base cutting edge which extends along the longitudinal axis of the drill body, said groove-base cutting edge transitioning at another blade corner which faces away from the drill tip into a groove-flank cutting edge, which extends transverse to the longitudinal axis of the drill body longitudinal axis,
• wherein a groove-chip rake face and a main free surface formed at the drill tip converge at the front cutting edge and enclose an angle defining a wedge shape, said groove-chip rake face extending substantially orthogonal to an exterior surface of the drill body and having a longitudinal plane congruent with a longitudinal axis of the drill body,
• wherein at the groove-flank cutting edge which faces away from the drill tip and at the groove-base cutting edge the groove-chip rake face transitions into further free surfaces which face radially outwardly, said further free surfaces adjoining the cutting edges in the rotation direction with a free angle,
• said blade corner of the main blade being spaced apart from the groove blade by a longitudinal offset,
• wherein during said inserting the groove blade generates a groove in the inner walling of the core bore, said blade corner of the main blade being guided in the groove with at least reduced cutting stress and without material engagement and being spaced apart by a free space from a groove flank of the groove, which groove flank precedes in a direction of the forward feed movement, wherein after generation of the groove by the groove blade an unprocessed material web remains on a groove side opposite the direction of the forward feed movement, said web being removable with the main blade.