Abstract: A mill is formed by a plastic rotating part, a high-hardness rotating part, a high-hardness stationary gear, and a plastic stationary part, such that the high-hardness rotating part and the high-hardness stationary gear are provided with a plurality of teeth complementary to one another for the grinding function. The high-hardness gear and the plastic stationary part advantageously have locking means enabling an automatic assembly of the mill, since the mentioned elements are able to easily rest relative to one another in the suitable position and fit together effortlessly.