In 3-axis NC (Numerical Control) machining, various cutters are used and the offset compensation for these cutters is important for a gouge free tool path generation. This paper introduces triangular mesh offset method for a generalized cutter defined based on the APT (Automatically Programmed Tools) definition or parametric curve. An offset vector is computed according to the geometry of a cutter and the normal vector of a part surface. A triangular mesh is offset to the CL (Cutter Location) surface by multiple normal vectors of a vertex and the offset vector computation method. A tool path for a generalized cutter is generated on the CL surface, and the machining test shows that the proposed offset method is useful for the NC machining. q 2004 Elsevier Ltd. All rights reserved.