This disc assembly with hub is the ground-engaging component that opens the seed furrow on a grain drill. It rotates on its hub as the coulter arm presses it into the soil, creating a clean trench for the seed metering unit to deposit material behind it. A worn or bent disc causes uneven furrow depth, leading to inconsistent seed placement and emergence. The original manufacturer machines the hub bore and disc face to the same concentricity as the original assembly, so no shimming or bushing is required during installation. On reinstall, verify that the hub rotates freely on its spindle and that the retaining hardware is tightened to the specified torque.