Abstract: A vibratory drive for use with a screening machine for draining and/or sizing of grain solids, the drive having two eccentric shafts which are driven synchronously and in counterrotation and which have different unbalanced masses 7, 8. The eccentric shafts are arranged as near as possible to the mass center 16 of the screening machine. The angle of the mass forces of the unbalanced masses 7, 8 of the eccentric shafts includes an angle of 60.degree. to 90.degree., preferably 90.degree., between the main direction of oscillation 18, i.e., the long axis 19 of the ellipse oscillation as a resultant of the centrifugal forces, and the zero line 17, i.e., the tie line of the eccentric shafts.