The improved geometrical accuracy and better surface finish of worms are required, especially in automobile industry. To meet this requirement, whirling process has been used in the manufacture of worm. Whirling process is a cutting process in which a series of cutting edges on the whirling ring remove material by turning over the rotating workpiece. In this study, cutting characteristics of the worm in whirling process has been analyzed. The undeformed chip models of front and side cutting edges were established. Using the undeformed chip models and DEFORM software, cutting force analyses are carried out. The calculated cutting force imposed on the tool is nearly the same as the sum of the forces calculated which are separately imposed on the front and side cutting edges.