During the last decades, many researches and applications have been conducted on machining features modeling and classification. Although several approaches have been used in the domain of Computer-Aided Process Planning (CAPP), the consideration of freeform shapes has not been well explored at present. This paper aims to provide an up-to-date review of machining features and its conformance with STEP-NC (STEP compliant Numerical Control). A new method based on discrete shape representation, differential geometry and graph theory is developed for freeform machining feature characterization and classification. The effectiveness of the proposed method is demonstrated through an example of a blade part.