A hammer (5) for a beater mill used to process coal, biomass material and other materials is provided having a hammer body (11), an impeller head (13) at a first end of the hammer body (11), and a bore (15) at a second opposite end of the hammer body (11). The impeller head (13) is detachably connected to the hammer body (11) by a base plate 17. Base plate (17) has a first side with a protrusion (21) and at least one bolt (29) protruding therefrom and a second opposed planar side with a crushing member (19). Protrusion (21) and at least one bolt (29) detachably connects impeller head (13) to first end of hammer body (11).