Friction and cutting of cobalt-free tungsten carbide using a monocrystalline diamond tool were examined using lubrication oils, such as water-miscible cutting fluid, sulfur-based extreme-pressure additives, zemetril-silicon, oleic acid, and zinc dialkyldithiophate (ZnDTP). The tool wear was greatest under zemetril-silicon, followed by water-soluble coolant, and was smallest under ZnDTP. Chipping was greatest under water-soluble coolant, followed by sulfur-based extreme-pressure additive, and smallest under ZnDTP. Cipping contributes to tool wear more than abrasive wear. Chipping wear is minimized under ZnDTP resulting in 0.022μm Ra after 177 m cutting.

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Ultrasonic machining is suitable for the high hardness and brittleness of ceramics materials, etc. However, the machining rate is slower than general cutting. To overcome this drawback, ultrasonic machining was combined with CO₂ laser machining under various conditions on SiC. The changes in machining depth, machining accuracy, and tool wear were examined. The results confirmed that the best laser irradiation conditions were dependent on depth of ultrasonic machining. In conclusion, air was used as the assistance gas when the machining depth was 700μm, and the most effective conditions were laser power 150 W and scanning speed of 1000 mm/min.

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This study was performed to investigate the adhesion of coatings on grinding surfaces using scratch testing as a function of surface roughness. Five types of grinding wheel were used to make carbide tip surfaces. Two types of coating were investigated: TiAlN and CrSiN. The coating adhesion tended to become stronger with smaller surface roughness. In particular, the coating adhesion was good in the case of surface roughness under 2μm for a coating. Differences in the grinding surface resulted in differences in coating-covered surface area.

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When thrust force directional vibration-assisted grinding is applied, the motion of the cutting edge is determined as a function of cutting speed, ultrasonic frequency, and amplitude. The motion of a sine wave can be calculated at each cutting edge. In the 2nd report, it was suggested that a phase shift of the abrasive grains removed material intermittently. Here, cutting test of single-crystal Si demonstrates that the cutting motion including the phase shift was precisely produced. Thus, ductile mode cutting of Si was obtained in the phase shift >0.2μm, and the cutting surface was almost flat. Based on these results, the design of a multi-cutting tool for flat surfaces was examined. The cutting edge space of the cutting tool was calculated at an ultrasonic frequency of 40 kHz, amplitude of 1μm, and cutting speeds of 120 and 960 m/min, to achieve ductile mode machining for flat surfaces.

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In the treatment of marginal periodontal disease, the root surface of the dentin must be cleaned smoothly for relief of inflammation and recovery of periodontal tissue. At present, cleaning of the dentin surface is performed by curettage using a dental scaler with a steel cutting edge at the tip of the instrument. The authors evaluated surface integrity, such as smoothness and depth of curetting marks, after curettage using a scaler. A simulation system of dental curettage was established with a customized jig holding the cutting edge of the scaler and used to slide the cutting edge on the dentin surface with a constant perpendicular force. The surface roughness was measured and the features of curetting marks were examined microscopically.

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