Abstract: A collet end effector comprises two jaws pivotably mounted in a housing for movement between an open and a closed position. A collet sleeve surrounds the jaws and is slidably mounted in the housing for movement along the jaws toward and away from a gripping end of the jaws. Each of the jaws has a cam surface; the collet sleeve has collet bearings for riding along the cam surface. The cam surface has a ramp region configured such that as the collet sleeve moves toward the jaws gripping end while the collet bearings ride along the ramp region, the jaws move toward the jaws closed position. The cam surface also has a dwell region extending from the ramp region toward the jaw gripping end configured such that as the collet sleeve moves toward the jaw gripping end while the collet bearings ride along the dwell region, the jaws are maintained in the jaw closed position.