Abstract: The dynamic stability of variable feed cutting processes is studied by cutting test and theoretical analysis. Through this study the chatter threshold is determined, the limiting width of cut and the frequency of chatter computed and measured. Formulae for the coefficient of overlapping is developed and the relationship between the limiting width of cut and coefficient of overlapping is found. Meanwhile a new hypothesis of chatter to explain the dynamic stability of variable feed cutting processes-that of "restraint-excitation -restraint" chatter mechanism is tentatively proposed. The influence of forced vibration upon self-excited cutting vibration is also investigated. On this basis, it is concluded that the dynamic stability of longitudinally variable-feed cutting process is higher than that of uniform feed cutting process. Finally, the practical implication in industrial application is discussed.