This product is used for the de-stoning of bulb-shaped and tuberous products. The machine consists of a sheet metal casing that houses an earthy lump/stone removal conveyor belt, a product discharge conveyor belt, and a double bearing-supported screw shaft with a frequency-controlled electrical motor. Since the RPM (revolutions per minute) directly relates to the upward pushing motion of the water, the separation between the floating and sinking material can be adjusted very precise. Only one paramater has to be adjusted in order to change the setting.