FIELD: machine building.
SUBSTANCE: mechanical grinding system intended for grinding of lignocellulosic material and having opposite plates of a refining machine. At least one of the plates includes a fibrous material inlet zone located radially inwardly from the grinding surface, and outlet of ground fibrous material, which is located radially on the outer side of the grinding surface. At that, the grinding surface includes knives and grooves, where each knife has the front edge between a section of side wall of front edge and upper ridge of the knife, and surface of upper ridge has a flat surface passing between front edge and rear edge of the knife; front edge is oriented in the rotation direction of the opposite lying plate, and front edge has an internal angle comprising 150-175 degrees, between upper section of side wall and upper ridge, and upper section of side wall passes from upper ridge to at least the middle of front edge between upper ridge and bottom of one of the grooves adjacent to the knife, and each knife has rear edge forming an internal angle that is less than internal angle of front edge, and rear edge is located between upper ridge and rear edge of the knife.
EFFECT: invention allows minimising impact forces and shear of fibrous material, which occurs in this connection, and maximising compression pulses for material grinding.
