An apparatus comprising a pair of associated chopper drums, including a top chopper drum and a lower chopper drum. The chopper drum defines an axial cylindrical bore having a rotational axis into which is mounted a drive shaft (not shown) that is keyed radially to drive the chopper drum. Radially spaced from the rotational axis are a plurality of outwardly facing recesses defined by walls of a body of the chopper drum. Each recess extends longitudinally along the periphery of the chopper drum end-end to provide a recess for mounting a corresponding plurality of cutting blades. Each recess is defined by a longitudinally extending lower wall and an opposed and circumferentially spaced. The cross sectional profile of the chopper drum is generally consistent throughout its length and includes a plurality of ridges and troughs with the ridges built up to define therein the recesses, the ridges being interposed by the troughs. A higher side wall provides support for the cutting blade and is inclined relative to a plane extending radially outwardly from the rotational axis. The opposed smaller side wall supports a wedge clamp.
