At present, both preliminary and final HSM is recommended to be carried out according to the scheme of cut-down milling. Processing of reinforced and unreinforced polymers is also recommended to be carried out at cut-down travel. The main problem associated with cutdown milling is caused with insufficient dynamic stiffness or the presence of backlash in the feeder table. The proposed concept of machining allows eliminating fundamentally the influence of dynamic stiffness and the presence of backlash in the table feeding mechanism on the quality of machining with GUS makes it possible while retaining the advantages of cutdown milling. Some kinematic schemes for high-speed machining by milling and turnmilling are given in the paper. The schemes for forming geometrical roughness components in such machining and calculation formulas are presented. The results of experimental studies of roughness formation with disc cutters made of fiberglass composite material in high-speed machining are presented. The results obtained are compared with the calculated data.