The stability lobes are one of the most powerful tools to improve the productivity of the cutting processes when they are limited by chatter vibrations. The best known lobes correspond to the traditional chatter or Hopf bifurcations. In some cutting processes, like in milling or in interrupted turning, further lobes appear related to period doubling chatter or flip bifurcation. When the system has more than one dominant vibration mode, some variations appear in the lobes due to interaction between modes. The basic mathematics for the appearance of these new lobes is shown in the paper. If the phenomenon is studied in the frequency domain, the period doubling or flip lobes can be considered as a special case of the interaction between modes. The interaction is studied using the Semi-discretization (SD) and Multi-frequency (MF) method.