This rotary chopper knife is a replaceable cutting blade mounted on the chopper drum of a forage harvester. It severs the crop material as it passes between the drum and the stationary shear bar, reducing stalk length for uniform processing. The knife is secured to the drum by its mounting holes and is positioned to maintain a consistent clearance with the shear bar. A worn or dull knife increases cutting force, produces uneven chop length, and places higher load on the drive system. The manufacturer machines this knife to the same thickness and hole spacing as the original, so it seats correctly on the drum without shimming. On installation, tighten the mounting bolts to the specified torque and check the drum-to-shear-bar gap.