When the cutting edge is in contact with the workpiece, the cutting edge applies a compressive drag onto the work- piece which gradually increases until the ultimate strength to initiate cutting off is reached. Such a pressure disappears suddenly after the workpiece is cut off. The cycle repeats and induces an equal and opposite reaction to the cutter blade edge. It may cause elastic deformation at the cutting edge. Such reciprocated impact will act on very small surface contact regions. After many repeated cycles, the cutting edge chips off due to contact fatigue. The depression, shown in Fig. 12, provided evidence of the presence of the contact fatigue wear[4]. Obviously, this kind of wear is one of the main causes of initial wear pit at the cutting edge. Such effect unsharpens the cutting edge. As the sharpness of the cutting edge decreases, i.e., the curvature of the cutting edge becomes greater, this effect gradually decreases.