In the machining of traditional metallic materials, high hardness is primary property that tool designers are committed to pursuing to improve wear resistance. In this study on machining of Nomex honeycomb composites (NHCs), it was revealed that high toughness is the dominant factor for wear resistance of disc tool. A comparative study was designed, including normal characteristics, hardness enhancement, and toughness enhancement. The material properties of the three pre-treatment methods were compared. The importance of toughness and hardness was evaluated from tool wear and surface quality. The results indicated that toughness-enhanced tools could be machined to produce the sharper cutting edges. Simultaneously, the toughness-enhanced tool was better suited to the high periodic cyclic impact loads in ultrasonic vibration machining.