Abstract: Geometric modeling and numerical control machining principle of shoe last are introduced. With an analyzing of the cutter location point generating theory and the fitting error of shoe last machining, a new method is presented for tool radius compensation to deal with the space curves machining. An algorithm is suggested which consists of interference avoiding, undercut region machining and a resolvent is carried out for some special problem which occurred on the polar coordinate, this way can also accommodate to other non-circle space curves machining.

Key words: Interference-free tool-path, NC machining, Polar coordinate, Shoe last, Space curves