Threshing and separating system with helical slats for an agricultural harvester

An agricultural harvester defining a longitudinal axis in a travel direction of the harvester, comprising:

• a chassis;
• a threshing and separating system carried by the chassis, the threshing and separating system comprising:
• a concave;
• a shaft defining an axis of rotation which is parallel to the concave and transverse to the longitudinal axis;
• and
• a plurality of slats rotated by the shaft and configured to move crop material against the concave, each of the plurality of slats having a helical shape winding around the axis of rotation,
• wherein the plurality of slats includes a first set of slats being predominantly on a left side of the shaft and having a left-handed helical shape, and a second set of slats being predominantly on a right side of the shaft and having a right-handed helical shape, and
• wherein at least one slat of the first set of slats is staggered relative to a closest slat of the second set of slats, such that a portion of a slat length of the at least one slat is overlapped with one or more adjacent slats of the second set.