Milling polymers have particular complications, especially for their low machining temperatures, so it is important to have the optimal variables to obtain the best nominal value for the final manufactured product. This article compares the engineering tolerance for two different milling strategies, parallel "Raster" and spiral trajectories, to machining concave and convex forms. This investigation concludes, for machining concave forms either Raster or spiral trajectories have good shape tolerance.On the other hand, for machining convex forms spiral trajectory showed the best engineering tolerance, getting a nominal radius closer to the theoretical radius than the Raster trajectory.