Circular milling operations are used to enlarge die and mold cavities, cylinder bores and machine airframe pockets. The tool attached to the rotating spindle follows a circular trajectory with a machining feed rate, while gradually moving forward in the direction of global axis with a step over feed. This paper presents the mathematical model of chip removal mechanism by predicting time varying cutter-part intersection as the cutter travels along the circular path. The vibration free cutting forces are predicted and experimentally verified. The dynamics of the process are modeled by considering vibrations of the end mill in two directions. The chatter stability of circular milling is modeled both in frequency domain and with a numerical model based on time finite element analysis which considers time varying immersion and directional factors. The resulting stability solutions are compared against experimental results.