A theoretical model was defined to predict cutting forces in drilling of polyamide. This model was not built in analogy to metal cutting but starting from the visco-elastic behavior of the workpiece material. The drilling thrust and torque were assumed to be a logarithmic function of the ratio between a characteristic time of the material and a process time. Drilling tests were carried out to experimentally evaluate the thrust and torque in dependence of drilling speed and feed rate. The experimental data are in good agreement with the predicted logarithmic trend, except at high feed rates at which a plateau is observed. The chip formation mechanism was recognized to affect the thrust and torque dependence on feed rate so that the theoretical model was opportunely corrected.