The quality of the flat and cylindrical surfaces of the gear pump pinions is a restrictive condition for a suitable work. The required quality of these surfaces is very high, R = 0,04 – 0,08 µm. As well, there are restrictive conditions input for the form and positioning a deviations. So far, the manufacturing of these surfaces used to be achieved by grinding and no one could guarantee that the surface roughness was in accordance with the technical documentation. The presented constructive solution allows obtaining a good quality of the flat and cylindrical surfaces. It uses a superfinishing attachment that can be mounted on the engine lathe.