In this paper, a generalized tool life model that considers nonstationary cutting was developed. In particular, the model was conceived for predicting the life of the tool when Spindle Speed Variation SSV , one of the most effective techniques for suppressing regenerative chatter vibrations, is used. The proposed formulation takes into account the main cutting parameters and the parameters associated to the SSV . A dedicated experimental campaign of turning tests was carried out and the data were used to develop the model. A proper validation was even carried out performing additional tool life tests. It was found that the generalized formulation can be used for predicting the tool life both at constant spindle machining CSM and adopting SSV within the maximum estimating error of 6%.