Dosier is dosing in English, to control specified amount of oil input. My understanding is that there should be two holes on your fixture as you mentioned, and this dosing screw is only for filling oil. Also you can use this hole to drain out the oil, but at the same time you need to remove theSPANN-SCHRAUBE, you can figure out why. Normally during production nobody touches the dosing screw. It doesn"t help you on roundness.