Abstract: A centrifugal mill for disintegrating fibrous material is provided with a cylindrical grinding track in front of a conical grinding track. The grinding tracks are corrugated and are adapted to cooperate with rotary grinding blades. The corrugation of the cylindrical track is coarse compared to that of the conical grinding track. The charging port of the mill is arranged at the larger cone diameter and the discharging port for the ground stock is arranged at the smaller cone diameter. Means are provided for conducting a controlled air flow from the larger cone diameter to the smaller one through regular spaces between the rotary grinding blades in the peripheral direction thereof.