The geometric characteristics of a machined surface have an important role to determine the performances of a mechanical part. Recently, many research efforts have been made to model and predict the surface topography resulting from machining operations. This work presents a form-shaping based approach to the prediction of the machining errors of a milled guide. Given the tool shape and the nominal tool trajectory, it is possible to simulate the effects of machine errors from different sources (e.g. thermal, geometric dynamic, etc.). The result of the simulation is a discrete point description of the milled surface. The use of a generalized kinematic model of the machine tool, based on a link-chain representation, gives a simple but effective way to implement the model. The result of the simulation can be used both to verify the effects on the milled surface of known errors and to study the effect of possible strategy for error compensation.