The study of this project has been carried out to analyse how the angle between feed direction and flexibility direction (𝜃 ) affects the milling process stability. Through this project, the aim is to determine whether the critical Depth of Cut (DOC) depends on 𝜃. In order to carry out this purpose, analytical and experimental results have been compared. The analytical calculations have been carried out to obtain the stability lobe diagram and a stability limit depending on 𝜃 , to compare them with four circular milling experiments. They increase continuously the DOC and also varies the Width of Cut (WOC), in addition different spindle speeds were utilized to perform them. The flexibility is fixed in the 𝑥 -axis and the feed direction changes continuously along the experiment, which allows the interaction between the critical DOC and all possible 𝜃 .The most relevant experiments were the second and third, as they showed the largest self-excited values. Moreover, it is determined that both analytical results correspond precisely, but it is considered that the experimental results do not match the analytical ones. No results are found that can be used to determine that 𝜃 influences the critical DOC. Furthermore, some results align with previous research in this field and some of them lead to future investigations.