Abstract: The adjusting device for a rotary tool contains a flexible spring, with radially adjustable cutting plates. The holder can be deflected relative to a support by a setscrew, with a pressure zone on a threadless circumferential part jointly with a complementary zone on the holder forming a wedge surface pair. During its adjustment, the cutting plate experiences a radial displacement. The annular scale has graduation marks and at least one orientation mark A conical section of the adjusting screw (8) has an angle (?/2) of 4.5 to 24°, the pitch of the setscrew (8) is 0.1 to 0.3 mm and the adjustment range is 0.1 to 5 mm.