A harvesting machine (12) is disclosed. The harvesting machine (12) comprising: a main frame (210)； a rotor assembly rotatably coupled to the main frame (210) and configured to move crop material； a top frame (202) movably attached to the main frame (210), the top frame (202) forming a passageway (226) for crop material between the top frame (202) and the rotor assembly； a bottom frame (204) movably attached to the top frame (202) or main frame (210)； a plurality of knives (208) movably attached to the bottom frame (204) or the top and bottom frames (202, 204), the plurality of knives (208) extending through slots (224) in the top frame (202), the bottom frame (204) engaging an indentation on a non-cutting edge of the knives (208) to maintain the plurality of knives (208) in a locked condition； an actuator (240, 241) operatively connected to one of the top and bottom frames (202, 204), the top and bottom frames (202, 204) and the plurality of knives (208) being in a raised position when the actuator (240, 241) is in a first position, and the top and bottom frames (202, 204) and the plurality of knives (208) being in a lowered position when the actuator (240, 241) is in a second position, which enlarges the passageway (226) between the top frame (202) and the rotor assembly and at least partially retracts the knives (208) through the slots (224) in the top frame (202) while maintaining the knives (208) in the locked condition.
