In this paper an analytical model for stability limit predictions in turning and boring operations is proposed. The multidimensional model includes the three-dimensional geometry of the processes resulting in an eigenvalue problem. In addition, a model for the chip thickness at the insert nose is proposed to observe the effect of the insert nose radius on the chatter stability limit. The model represents a development over existing ones due to accurate treatment of the multidimensional process dynamics and geometry, and resulting practical formulas for stability limit predictions. Chatter experiments are conducted for both turning and boring in order to verify the model predictions, and overall, an acceptable agreement is observed.