This gear transmits drive from the corn-header driveline to the rotating cutter assembly. It meshes with the mating gear on the cutter shaft, converting input speed into the required cutter rotation for chopping the crop. A worn gear produces irregular cutter speed, leading to uneven chop length and increased load on the upstream driveline components. The original gear is machined to match the tooth profile and hardness of the mating gear, which prevents accelerated wear on both parts. On replacement, verify the backlash between the two gears and adjust the shimming as needed.