PURPOSE: To improve the life of a liner by linearly disposing plural wear resistant inserts into the liner along a concentrated wear path and constituting these inserts of blanks having the higher wear resistance than the wear resistance of a liner blank.

CONSTITUTION: While the feed material supplied from the center of a hub 86 passes a pocket 96 by rotation of a rotor 20, a feed material layer 124 is formed along a path 126. The succeeding feed material collides against the feed material layer 124 along the path 126 and is then released from the rotor 20. This feed material comes into collision against an ambient anvil and is crushed. The wear of this path 126 is maximized and is made into the concentrated wear path. The plural wear resistant inserts 128 are nearly linearly embedded into the wear resistant liner 118 along this concentrated wear path 126. The inserts 128 are formed of the wear resistant blank having the higher wear resistance than that of the liner 118. Then, the abrasion generated in the concentrated wear path 126 of the liner 118 is lessened by the inserts 128, the life of the liner 118 is improved and the number of exchange times is decreased.