This investigation is aimed to predict the stable speed range for machining thin-ribbed structures with minimum deflection. Dynamic peripheral milling of a cantilevered free-free-free plate is considered to predict the stable speed range. The significant geometrical parameters considered here are thickness, length and height of the rib. Various thin ribs are modeled by changing the above-mentioned geometrical parameters in order to carry out the analysis. The cutting forces, which were measured experimentally, are applied as input for finite element analysis.Harmonic analysis is carried out for the rib models using which the stable speed range is determined. The influence of cutting forces on the deflection of thin ribs also has been studied. Generalized stable speed is recommended for thin-ribbed structures having different geometrical parameters.