Threshing for a combine harvester and a threshing

The present invention relates to a threshing mechanism for a combine harvester, having at least three processing scheduled the crop drums, which comprise an intended for threshing the harvested crop threshing drum, and at least two of the threshing drum in a conveying direction of the crop material through the threshing downstream drums, wherein • the drums each having a diameter, wherein the diameter of the threshing drum is greatest, • the drums are in an approximately concave running in the conveying direction, rising notional line stored, and • the diameter of the downstream to the threshing drums are successively smaller in the conveying direction. The present invention further relates to an in particular self-propelled combine harvester having a threshing mechanism such as well as a method for adjusting the threshing mechanism.