The number of models available for prediction of surface topography is very limited. The main reason is that these models cannot be based on engineering principles like those for elastic deformations. Most knowledge about surface roughness and integrity is empirical and up to now very few mathematical relationships relating surface parameters to cutting conditions are available. Basic models of kinematical roughness, determined by the tool profile and the pattern of relative motions of tool and workpiece, have been so far not reliable. The actual roughness may be more than five times higher due to error motions, unstable built up edge and changing tool profile due to wear . Tool chatter is also affecting surface roughness, but its effect is normally not included in prediction of surface roughness, since machining conditions which generate chatter must be avoided in any case. Finally, reproducibility of experimental results concerning surface roughness requires tight control of all influencing factors, difficult to keep in actual machining workshops. This introduces further complications in surface topography modelling. In the light of these considerations, a simple software tool, for prediction of surface topography of ball nose end milled surfaces, was developed. Such software tool is based on a simplified model of the ideal tool motion and neglects the effects due to run-out, static and dynamic deflections and error motions, but has the merit of generating in output a file in a format readable by a surface processor software (SPIP ), for calculation of a number of surface roughness parameters. In the next paragraph a description of the basic features of ball nose end milled surfaces is given, while in paragraph 3 the model is described.