A highly secure instrument adapter includes a handle with an internal locking and release mechanism which does not use a pushing release and which requires little physical effort to lock and release, yet provides a stable and secure connection between an instrument and the handle. The locking mechanism is comprised an ergometric handle having an open handle cavity, a receiver having an internal threaded tubular body and a plurality of locking apertures, and a rotating collar having a limited range of rotation, a plurality of fingers that project outward from the flattened surface on a spacer structure, and a plurality of circular apertures placed alternately between said fingers.