A surgical apparatus comprises a body, an ultrasonic transducer, a shaft, and an end effector. The ultrasonic transducer is operable to convert electrical power into ultrasonic vibrations. The body comprises a pivotal trigger. The shaft couples the end effector and the body together. The end effector comprises a clamp arm and an ultrasonic blade in acoustic communication with the ultrasonic transducer. The ultrasonic blade is operable to deliver ultrasonic vibrations to tissue. Pivotal movement of the trigger causes movement of the clamp arm. The shaft is operable to be selectively coupled and decoupled from the ultrasonic transducer. The apparatus comprises electro-mechanical means for coupling and decoupling the shaft from the ultrasonic transducer, and may further comprise means for preventing movement of the shaft as it is coupled to the ultrasonic transducer.