A coupling device and coupling method for the self-securing mechanical connection of two parts of a holding system for medical instruments, including a bolt element insertable into a bushing； wherein the bushing has a main body and, connected fixedly to the latter, a cone sleeve which tapers conically at its free end, wherein a cage sleeve acted upon by a spring and guiding clamping bodies is inserted axially movably into the cone sleeve and can be moved between an uncoupled position, a release position and a locking position. The clamping bodies in the locking position can be latched into a coupling groove of the bolt element by means of the spring force. The inclined coupling groove flank, at the front in the insertion direction, of the bolt element encloses an angle α with the longitudinal axis of the bolt element, and the cone inner face of the cone sleeve encloses an angle β with the central sleeve axis. The coupling device is characterized in that, for self-securing connection, the angle α is greater than the angle β such that clamping bodies partially or completely latched into the coupling groove can be pressed into the locking position counter to the insertion direction by application of a tensile force to the bolt element.
