A simulation model is developed to study the dynamic characteristics of intermittent turning operations. Factors such as chip load, free-vibration of the toolpost structure, and nonhomogeneous hardness distribution in the material being cut are incorporated in the model. The principle of superposition is used in the formulation of the simulation algorithm. The impact between the cutting tool and the workpiece at the start of every cutting period during machining is treated as an initial value problem. The simulation model provides a quantitative evaluatior of the tool vibratory motion during the intermittent turning process. Study of the cutting dynamics based on the simulation results not only confirms the experimental findings, but also indicates that increasing the static stiffnes of the toolpost structure is an effective approach to control the tool vibratory motion. The determination of a probability of tool breakage under various spindle speed settings is presented as an example to demonstrate the practical applications of the simulation model developed in this work.