Abstract: A pump and metering apparatus includes a frame supporting a liquid container with a movable plunger therein for discharging respectively liquid which is drawn therein. A plunger is connected to a runner member, connected by a nut portion thereof which threadedly engages a screw rotatably mounted in the frame and coupled to a driving motor. According to the invention the nut portion of the runner member is movable in relation to the remaining structure of the runner member in the radial direction of the screw, such that the nut portion will be self-centering on the center axis of the screw.