This hub mounts the coulter disc to the seed drill or tillage machine frame. It provides the rotating interface between the stationary spindle and the disc, allowing the disc to turn freely as it cuts through soil. The hub contains the bearing assembly that supports the disc under load and maintains its alignment relative to the seed furrow. A worn hub produces wobble in the disc, leading to uneven slot depth and inconsistent seed placement. The hub is machined to match the original disc's pilot diameter and bolt pattern so the disc seats concentrically without shimming. When replacing the hub, inspect the bearing races and seals; install new seals and torque the retaining nut to specification.