A surgical instrument includes a housing supporting first and second actuators, an elongated shaft extending distally from the housing, and an end effector supported by a distal portion of the elongated shaft. A tensile member extending through the elongated shaft is coupled to the first actuator and the end effector such that first actuator may be manipulated to induce motion of the end effector. A locking mechanism associated with the tensile member selectively impedes motion of the end effector. The locking mechanism includes a collet disposed about the tensile member and a collet clamp for receiving the collet. Receipt of the collet into the collet clamp induces radial compression of the collet to impede the motion of the tensile member therethrough. An actuation member extending through the elongated shaft induces insertion and withdrawal of the collet from the collet clamp.