Although the conventional contour parallel tool path obtained from geometric information has been successful in making desirable shapes, it seldom considers the physical process concerns like cutting forces and chatters. In this paper, an optimized contour parallel path, which maintains constant MRR (material removal rates) at all times, is introduced and the results are verified. The optimized tool path is based on a conventional contour parallel tool path. Additional tool path segments are appended to the basic tool path in order to achieve constant cutting forces and to avoid chatter vibrations in the entire machining area. The algorithm has been implemented for two dimensional contiguous end milling operations with flat end mills, and cutting tests were conducted to verify the significance of the proposed method.