© 2021, The Brazilian Society of Mechanical Sciences and Engineering.The subject of this study is a new Process Damping Model approach for milling with flat end milling cutter. Dynamic model of the cutting system was modeled and applied for the milling operation. The machining process is developed mathematically as a complex dynamic cutting model with two degree of freedom. This cutting model is designed according to both friction forces due to contact with wavy surface and shear angle (φ) oscillations. Considering Process Damping Ratios (PDRs), shearing force equations of the system are mathematically modeled. This created process damping model is a complex model, and it enables to obtain process damping values and rates both due to the deflection of the insert and the penetrating of the cutting edge to the wavy surface. It is also explained how the total process damping of the cutting system will change and how the equations will be arranged accordingly. Comparative process damping rates were obtained by making modal analyzes to obtain structural constants of different length cutting tools. The experimental results determined were applied to the developed model, and it was calculated that the rate of process damping varies depending on the factors. The most obvious difference that distinguishes this study from others is the change, and amount of the PDR is estimated by the analytical calculation procedure which runs in reverse to the conventional Stability Lobe Diagrams.