During the threshing process 60 to 80 percent of the grain is now separated from the straw in the thresh­ing cylinder. If the efficiency of separa­tion in the cylinder could be increased, sufficiently, the straw rack of a com­bine could be eliminated. Research de­scribed in this paper was conducted to investigate the efficiency of separa­tion of a new threshing device. A threshing cone with the material moving axially from the small end of the cone to the large end, provides a device for increasing the time that the material is subjected to threshing and separating forces.