Screw spindle pump having a stop surface axially adjacent to an end surface of a running spindle

A screw spindle pump, comprising;

• at least one running spindle not having a hydraulic axially just balancing;
• a housing and a drive spindle accommodated therein and the at least one running spindle which meshes with the latter and which has in each case two terminal end surfaces, wherein the drive spindle is hydraulically balanced so that during a pumping operation no or only a negligible axial force acts on the drive spindle, wherein a stop surface is provided axially adjacent to at least one end surface of the terminal end surfaces of the at least one running spindle, wherein the at least one running spindle is accommodated displaceably with an axial clearance perpendicular to the stop surface and is movable against the stop surface.