Abstract: The invention relates to a locking system for a rotatable part, in particular in arrangements in which two parts which can be rotated in relation to each other, for example a die and a punch in a stamping apparatus, have to be aligned exactly in relation to each other. In order to provide a positionally accurate mechanical locking system with a simple design, the invention proposes that a gearwheel (3) having an end-side and/or axially effective toothing system (4) is connected to the rotatable part (2) fixedly in terms of rotation, and that at least one toothing segment (5a-5f) which can move to and fro in the direction of the axis of rotation and/or parallel to the axis of rotation of the gearwheel is arranged over the circumference of the gearwheel, wherein the teeth or gaps between the teeth of the toothing segment and gearwheel can be brought into engagement without play.