In this paper, a new ternary-mechanism cutting force model including chip removal, flank rubbing and bottom cutting effects is developed for the first time to predict cutting forces in flat end milling. In this model, total cutting forces are treated as a summation of bottom edge-induced forces and flank edge-induced forces due to chip removal and flank rubbing effects. Cutting force coefficients are efficiently calibrated in three steps: calibration of the coefficients related to the chip removal effect using linear regression of the transformed experimental cutting forces, establishment of an explicit equation to bridge flank rubbing/bottom cutting effects and the remaining experimental force components without chip removal effect, and determination of the flank rubbing and bottom cutting coefficients by solving the equations from the second step. Based on rigorous analyses and in-depth discussions, it is definitely demonstrated that the ternary-mechanism model exhibits a remarkably good accuracy and it may be used to reveal the underlying damping mechanism of flat end milling process. Meanwhile, cutting force coefficients can be reliably treated as constants. Their calibrations can be routinely and efficiently made only with a single experiment test when compared to the traditional constant cutting force models. To highlight the perspective applications in an industrial setting, the proposed model is compared with one existing lumped model and tested for different combinations of experimental parameters including cutter/workpiece couple, depth of cut, milling type and feed per tooth.