Abstract: A tool is to be automatically connected to a robot arm in well-defined angular position such that a sufficiently high torque is transmitted. The robot arm has a conical recess extending over a tool cone. A threaded sleeve is rectilinearly guided in the tool cone and displaceable with respect to a spring. A flange of the threaded sleeve engages an annular shoulder. A threaded spindle extending with a threaded head in a recess is mounted in the robot arm. The threaded spindle first pushes the threaded sleeve back against the action of the spring, such that the spindle engages the threaded sleeve with a well-defined force. Then the threaded head is screwed into the threaded sleeve and through the flange pulls the tool and the robot arm against each other by rectilinear movement. The conical surfaces and of the recess and the tool cone ensure the torque transmission.