An apparatus and method for controlling a clearance between the blades of a turbomachinery component and flow forming surface are disclosed herein, and includes controlling the clearance by moving the surface axially relative to the turbomachinery component. In one embodiment the apparatus includes an impeller rotatable about a first axis, a shroud encircling the impeller, and a first ring encircling the first axis. An actuator is operably engaged with the first ring to pivot the first ring about the first axis. The apparatus also includes at least one cam engaged with the first ring and at least one cam follower engaged with the shroud. Pivoting movement of the first ring about the first axis results in the at least one cam urging the at least one cam follower and the shroud along the first axis to vary a distance between the plurality of blades and the shroud.