Ultrathin workpieces about 0.5 mm in thickness roll back significantly after surface grinding. In this study, the interaction of grinding temperature and residual stress of the workpiece were investigated to clarify the cause of workpiece curvature experimentally. The results indicated that there is a critical grinding temperature dominating over the direction of workpiece curvature after grinding. The residual stress of the workpiece also changes from the compressional state to the tensile state with curvature direction. The critical grinding temperature where the curvature direction and residual stress changes was confirmed to be close to the transformation temperature of the workpiece material. These results indicated that the curvature of the workpiece is caused by the residual stress of the workpiece surface due to transformation of the workpiece material with grinding heat.

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Ti alloys are important engineering alloys for advanced applications in aerospace engineering, airframe manufacture, and biomedical industries. However, Ti alloys are difficult-to-machine-materials because of their high chemical reactivity and low thermal conductivity. We attempted to improve the performance of cutting tools against Ti alloy by coating with B-C thin films containing Ti with high adhesive strength. Introduction of CH₄ gas during the sputtering process reduced the friction coefficient of the B-C films from 0.6 to 0.2, although their hardness remained above 15 GPa. We carried out experiments to optimize the deposition conditions of B-C thin films containing Ti and also to improve cutting properties of Ti-B-C-coated tools against Ti alloy.

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We investigated the reactivity of single-crystalline CVD diamond (100) surfaces milled using a Ga-focused ion beam (FIB) and modified by posttreatment (as-milled, vacuum heating, H₂ plasma exposure) with Al, which is a standard work material for diamond tools, using an energy dispersive X-ray spectrometer. In the case of as-milled surfaces, residual Ga ions on surfaces heated in contact with Al decreased more rapidly than those heated without Al. The presence of Al, which could not be removed by NaOH etching, was confirmed on the surfaces heated at over 673 K in contact with Al for FIB with an acceleration voltage of 20 – 30 kV, and at 773 K for FIB acceleration at 10 kV. These results suggest that the tips of diamond tools formed by Ga FIB milling may adhere to Al workpieces at temperatures over 673 K if the surfaces are not modified by appropriate posttreatment. No Ga or Al was observed on surfaces that were modified by posttreatment consisting of vacuum heating at 1373 K for 1 h or H₂ plasma exposure at 1200 K for 1 h even when heating at 573 K – 773 K in contact with Al, and thereafter etching was performed.

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Chipping at the exit side of drilled holes is an important quality for products made of fine ceramics. This study was performed to determine the chipping generation mechanism and to develop a novel method to reduce chipping in helical boring. Experiments were performed to verify when cracks are generated during boring and to determine their propagation behavior. The results indicated that the size of chipping at the exit side of drilled holes is dependent on the initial crack generated in boring. Therefore, helical boring for workpieces with pre-holes was carried out using a ball-end tool. The chipping was reduced and tool life was prolonged in comparison to conventional boring methods using workpieces without pre-holes.

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