The assembly comprises a coupling for direct or indirect coupling the core rod (15) to the lower punch (12) of a powder press. The coupling is configured as a magnetic coupling and comprising two coupling elements (20, 30), the first (20) of which is actively connected to the core rod (15) and the second (30) of which is actively connected to the lower punch (12). The magnetic coupling comprises several permanent magnets (24a, 24b, 33a, 33b) arranged at each coupling element. These permanent magnets (24a, 24b, 33a, 33b) are arranged and adapted to each other such that when coupling the two coupling elements (20, 30) the first coupling element (20) is automatically rotated by the effect of the field lines of the magnets (24a, 24b, 33a, 33b) into a predetermined angular position relative to the second coupling element (30).