A threshing system for use in an agricultural harvester. The threshing system includes a rotor and a perforated concave system. The rotor has a rotational axis. The perforated concave system is spaced radially outwardly from the rotor for passage of grain through perforations as the rotor moves crop material across the concave system. The concave system has at least one concave section having a rigid frame, pivotal members, and an arcuate movable member. The rigid frame has a plurality of sides rigidly coupled together. The pivotal members are pivotally coupled and extend to two of the sides of the rigid frame. The arcuate movable member interacts with the plurality of pivotal members to pivot each of the pivotal members as the arcuate movable member is moved along a segment of an arc generally about the rotational axis.
