This moving knife is the cutting element mounted on the rotating drum of the straw chopper. It interacts with a stationary counter-knife to shear straw and residue after the grain has been threshed. The knife is secured through its mounting hole and rotates with the drum assembly. A dull or damaged knife produces ragged cuts and increases the power draw on the chopper drive, which can lead to uneven residue distribution behind the machine. The manufacturer machines this replacement to match the original geometry so it seats correctly against the counter-knife without requiring shimming. When replacing, inspect the mounting bolts and torque them to specification.