A separating screen conveyor for sorting a material composed of large numbers of loose items or particles, into a first fraction having a first distribution of a property of the particles or items and a second fraction having a second distribution of said property of the particles or items, said first distribution being different from said second distribution; the separating screen conveyor comprising a row of shafts mutually spaced in a conveying direction, each of said shafts being rotatable about an axial center line thereof, extending transversely to said conveying direction, and carrying a row of radially projecting discs for intermittently urging material on the separating screen conveyor upward and in the conveying direction, the discs of each of said rows being mutually spaced in longitudinal direction of the respective shaft; wherein the discs of at least one of said rows are releasably clamped to the respective one of said shafts extending through openings in said discs, for allowing readjustment of the mutual spacing of said discs in said longitudinal direction of said shaft when in released condition, said discs each having a maximum width ( w) in said longitudinal direction of said shaft; characterized in that, the at least one shaft to which the discs of said at least one row are clamped has at least one strip oriented in said longitudinal direction of said shaft, projecting radially from a circumferential surface of the shaft and having a toothed surface, teeth of said toothed surface projecting transversely to the axial direction of the shaft and being arranged in a row with a pitch ( p) in said longitudinal direction of said shaft; said openings of the discs each have at least one recess closely fitting to the at least one strip, respectively, and having at least one surface having at least one tooth in engagement with the teeth of said toothed surface of said strip; and said pitch ( p) of said teeth of said strip is smaller than said maximum width ( w) of each of said discs in said longitudinal direction of said shaft. the separating screen conveyor comprising a row of shafts mutually spaced in a conveying direction, each of said shafts being rotatable about an axial center line thereof, extending transversely to said conveying direction, and carrying a row of radially projecting discs for intermittently urging material on the separating screen conveyor upward and in the conveying direction, the discs of each of said rows being mutually spaced in longitudinal direction of the respective shaft; wherein the discs of at least one of said rows are releasably clamped to the respective one of said shafts extending through openings in said discs, for allowing readjustment of the mutual spacing of said discs in said longitudinal direction of said shaft when in released condition, said discs each having a maximum width ( w) in said longitudinal direction of said shaft; characterized in that, the at least one shaft to which the discs of said at least one row are clamped has at least one strip oriented in said longitudinal direction of said shaft, projecting radially from a circumferential surface of the shaft and having a toothed surface, teeth of said toothed surface projecting transversely to the axial direction of the shaft and being arranged in a row with a pitch ( p) in said longitudinal direction of said shaft; said openings of the discs each have at least one recess closely fitting to the at least one strip, respectively, and having at least one surface having at least one tooth in engagement with the teeth of said toothed surface of said strip; and said pitch ( p) of said teeth of said strip is smaller than said maximum width ( w) of each of said discs in said longitudinal direction of said shaft.