This bushing fits onto the chopper-knife mounting bolt, positioning the knife at the correct spacing within the straw-chopper rotor. It sits between the knife and the adjacent external bushing, maintaining the specified gap for the knife thickness. A worn bushing allows the knife to shift, leading to uneven cutting and increased vibration in the rotor assembly. The bushing is machined to match the original bore tolerance, so the knife remains aligned without shimming. On reassembly, verify the bushing stack order and torque the mounting bolt to specification.