This spring applies the clamping force that holds the metering disc against the seed-plate housing in a precision planter. It sits between the clutch hub and the pressure plate; when the clutch is engaged, the spring compresses to transmit drive torque to the disc. A fatigued spring reduces clamping pressure, allowing the disc to slip and causing uneven seed spacing or missed singulation. The manufacturer specifies the free length, wire diameter, and number of coils to match the original assembly’s spring rate, so the clutch engages and disengages at the correct force threshold. On reinstall, verify the spring is not collapsed or distorted before fitting it into the hub pocket.