In one aspect of the invention, a rotary impact mill has a milling chamber defined by a housing with an inlet, an outlet, and at least one wall. A plurality of impact hammers located within the milling chamber are fastened to and longitudinally disposed along a rotor assembly that is connected to a rotary driving mechanism. At least one of the impact hammers has a plurality of inserts arranged adjacent one another in a row and attached to a body of the hammer, wherein a first end of at least one insert is complementary to a second end of an adjacent insert.