At the beginning of article a 3D view of machined surface has been presented and correctness of form profiles registration on milling machine verified. A number of tool materials, recommended by producers for milling of hardened steel, were tested for wedge wear and form deviations. Components of the deviations coming from position changes of wedge corner due to its wear, deformation of machined system as well as tilt of face mill axis were compared. Comparisons were aimed at determining qualitative and quantitative impact of main factors on face milled surface form deviations so as to create models of their arising.