A device for coupling two parts includes a first part having a cylindrical adapting journal and a radial flat surface which limits the adapting journal by the base thereof and being radially protruded, and a second part having a receiving sleeve with a cylindrical internal surface. A clamping device, during clamping, enables the adapting journal to be inserted into the receiving sleeve and to be pressed thereto between the flat surface and a front surface. In order to guarantee an exact centering of the parts with the aid of simple means, the inventive receiving sleeve is provided with a lower conical part diverging from the internal cylindrical surface towards the front surface and the adapting journal is provided with an elastically deformable centering ring which is arranged at the level of the base and is provided with an external conical part complementary to the lower conical part.