An axial flow combine of the type embodying threshing and separating means in the form of a generally cylindrical casing within which a vaned rotor operates and which defines a threshing region and a separating region. Helical impeller vanes on the forward end of the rotor impel the crop material rearwardly into the threshing region for conduction therethrough and from thence into and through the separating region. To enhance the capacity of the casing and rotor to handle crop material, a pair of transverse sheets which extend at a slight angle to each other so that one sheet is slanted in one direction relative to the rotor axis and the other sheet is slanted in the opposite direction, cooperate to establish, in effect a front wall for the casing. These sheets cooperate with the rotating impeller vanes to receive the backlash material which issues from the impeller and direct it forwardly into the working region of the latter.