Mathematical equations were established and the following regularities of the plane milling process of wood materials were analyzed: the effect of the cutting edge inclination angle on the chip exit angle, influence of the cutting edge inclination angle on the speed of chip movement along the blade and exit speed of the chips from the cutting zone, the dependence of the chip exit angle on the friction coefficients of the chips on the processed material surface and along the blade surface (the friction coefficients were determined from the results of the experimental measurements), and influence of the mill rotation frequency on the chip exit angle. The milling of the chipboards with various mill designs was performed at different cutting conditions (diameter = 7 mm to 24 mm, number of cutting elements = 1 to 3, cutting edge inclination angle = -5° to 20°, frequency of the mill rotation = 3000 min^-1 to 24000 min^-1, feed per tooth = 0.1 mm to 1.5 mm). The process of chip exit from the cutting zone was photographed, and the chip exit angles were measured. A comparison of the values of the chip exit angles obtained from the experiments with those from the calculations based on the developed mathematical equations showed a high convergence.