A surgical tool can comprise an interchangeable end effector, a handle assembly, and a shaft assembly. The interchangeable end effector may comprise a first jaw member including a first electrode, and a second jaw member including a second electrode. The first jaw member may be moveable relative to the second jaw member between a first position and a second position. The handle assembly may be proximal to the surgical end effector. The shaft assembly may extend between said handle assembly and the interchangeable end effector. The shaft assembly may comprise a rotary drive shaft configured to transmit rotary motions. The rotary drive shaft may be selectively axially moveable relative to the shaft assembly between a plurality of discrete positions. A coupling arrangement may be for releasably attaching the interchangeable end effector to the shaft assembly.