The article focuses on vibrations generated in the process of end milling of thin-walled elements (TWEs) during the time of part-tool contact. It is shown that the nature of vibrations and the parameters of the machined surface depend on belonging to a certain vibrational speed zone. The example of conventional milling shows that vibrations occurring in the 3rd speed zone are not self-induced but belong to a specific type of free vibrations and are classified as attendant free vibrations (AFV). Based on the empirical data and their statistical analysis, statistically significant relationships between the physical characteristics of the AFV and the initial conditions of TWE milling have been estimated. For the first time, the paper shows that the macrogeometry of the machined surface as a key parameter of the high-tech parts’ surface quality, is formed as the heredity of the waviness on the cutting surface formed by the AFV. Based on the performed analysis, a correlation matrix between the initial cutting conditions, physical characteristics of the AFV, and output parameters was formed, which is the theoretical basis for determining ways to control the shaping process during end milling to obtain the proper quality of the machined surface.