A threshing mechanism is formed with a first threshing drum and a second threshing drum disposed one behind the other in a direction of crop flow. A first concave encloses the first threshing drum and the second threshing drum in sections in a circumferential direction. A second concave encloses the second threshing drum in sections in the circumferential direction. The concaves are displaceable in a radial direction of the threshing drums and are formed with at least one crop-processing device disposed at the first concave. The first concave and the second concave are swivellable about a common axis connecting the concaves. The enclosure of the second threshing drum by the first concave and the second concave is approximately identical.
