Abstract: A wet comminuting machine is provided with a sieve which is located at the mill base outlet and has orifices of such dimensions that they block the passage of grinding medium. Opposite the exit surface of the sieve a plate, which can be moved toward the sieve, is provided, on the side facing the sieve, with elements for pushing through the orifices of the sieve, and can be moved manually, pneumatically, hydraulically or electrically by means of a connecting rod. The elements of the movable plate are arranged in alignment with the orifices of the sieve, and are in the form of strips or spikes, depending on the particular design of sieve.