A process geometry model determines engagement angle and instantaneous uncut chip thickness which forms basis in predicting cutting forces and surface quality in micro-end milling operation. This paper presents a process geometry model incorporating cutter runout, elastic recovery of work material and minimum chip thickness. These characteristics are incorporated effectively by realizing different engagement cases that are likely to occur during micro-milling. The model considers interactions of tooth trajectory under consideration with surfaces generated by previous teeth to develop a realistic process geometry model. It has been demonstrated that the inclusion of tooth trajectory interactions has significant effect on prediction accuracy of a model. The results are also substantiated by conducting machining experiments at various cutting conditions. © 2016 The Authors