Service Tip #4: Ensuring Drill Accuracy

To get the most accuracy with any Great Plains Drill, calibration is a must. Seed rate charts that are supplied with the unit or found on-line should be used as a starting point only! Follow the operator’s manual closely when performing the calibration. The time spent on this step can save valuable seed and time if the drill is not set properly before going to the field.

Seed Cup Calibration

To ensure even seeding across the drill, and to verify scale setting to seed cup positioning, a periodic seed cup calibration should be performed per the following:

  1. The seed calibration tool (part number 817-459C) is used to verify seed cup accuracy. If you don't have one, talk to your local Great Plains dealer. Each tool can be used to measure both small and large seed cups.

  2. Loosen the seed rate handle by unscrewing the wing nut (1) located on the underside of the handle. Set the seed rate handle to 60.


  3. Insert the calibration tool (817-459C) into the top side of the seed cup. Depending on which seed cups are present will determine the placement of the tool.
  4. If the small seeds cup is present with a 1¼" opening, use the 5/8" side of the calibration tool.


  5. If the larger seeds cup is present with a 1¾" opening, use the 7/8" side of the calibration tool.


  6. Once the calibration tool has been placed into the seed cup. Slide the seed rate handle until the feed wheel presses up tightly against the calibration tool. Re-tighten the wing nut.
  7. With the feed wheel pressed tightly against the calibration tool, the seed cups are now set at exactly 50%.
  8. The brass gauge should line up with the notch in the center of the seed adjustment handle at 50%. If the seed rate handle does not line up at 50%, loosen the two screws (2) holding the brass gauge and slide the gauge until the lever and gauge are lined up exactly at 50%. Re-tighten the screws.