Pump or motor for liquid or gaseous media - having working spaces which are arranged between working faces which lie opposite one another and are symmetrical with respect to their respective rotational axes, - having in each case one spur toothing system on the two working faces, the teeth of which spur toothing systems, which are assigned to one another, delimit the working spaces by way of contact lines which run radially and engage into one another, - having a defined corresponding angle between the respective axes of the two working surfaces, - having a working part which can be rotated about its axis and has a spur toothing system for receiving one of the working faces, - having a spherical radial boundary of the working part or the working faces for sealing mounting on a partially spherical inner wall of a housing, - having a radial boundary of the working spaces by way of that partially spherical inner wall of the housing which engages around the working part and on which the working part is mounted such that it can tumble about its axis and seals radially on the walls, - having a rotating drive or output via a shaft, and - having in each case one inflow and one outflow to the ducts (21, 22) which form working spaces for the medium, - an oblique sliding plane being arranged between the shaft and the working part which is provided with a spur toothing system and a working face, with the result that rotating of the shaft leads to tumbling of the working part, or tumbling of the working part leads to rotating of the shaft, and - with the result that the other working face (on 10) which lies opposite the working part, with a spur toothing system which corresponds to the spur toothing system of the working part, is arranged so as to not corotate and therefore in a stationary manner in the housing, characterized in that, towards the oblique sliding plane, the shaft has a diameter which is increased in relation to its mounted section, and, in order to forward the liquid or gaseous media, the shaft has a connecting duct which runs in the shaft and is connected via the oblique sliding plane and openings in the working part to the working spaces. - having working spaces which are arranged between working faces which lie opposite one another and are symmetrical with respect to their respective rotational axes, - having in each case one spur toothing system on the two working faces, the teeth of which spur toothing systems, which are assigned to one another, delimit the working spaces by way of contact lines which run radially and engage into one another, - having a defined corresponding angle between the respective axes of the two working surfaces, - having a working part which can be rotated about its axis and has a spur toothing system for receiving one of the working faces, - having a spherical radial boundary of the working part or the working faces for sealing mounting on a partially spherical inner wall of a housing, - having a radial boundary of the working spaces by way of that partially spherical inner wall of the housing which engages around the working part and on which the working part is mounted such that it can tumble about its axis and seals radially on the walls, - having a rotating drive or output via a shaft, and - having in each case one inflow and one outflow to the ducts (21, 22) which form working spaces for the medium, - an oblique sliding plane being arranged between the shaft and the working part which is provided with a spur toothing system and a working face, with the result that rotating of the shaft leads to tumbling of the working part, or tumbling of the working part leads to rotating of the shaft, and - with the result that the other working face (on 10) which lies opposite the working part, with a spur toothing system which corresponds to the spur toothing system of the working part, is arranged so as to not corotate and therefore in a stationary manner in the housing,