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Milling tests were conducted in order to investigate the cutting performances of a binder-less PcBN tool in the machining of Ti-6Al-2Nb-1Ta (α-β type alloy) and Ti-15Mo-5Zr-3Al (β type alloy), which are used as surgical implant materials. In milling of the α-β type alloy, some micro chippings on the rake face of the tool were observed as a typical pattern of tool damage. In the case of the β type alloy, however, there were not only micro chippings on the rake face, but also many micro-flakes on the flank face. The occurrence of micro-flakes on the flank face influenced the structural strength of the cutting edge, and finally caused it to fail. Therefore, the rate of tool damage in milling of the β type alloy was higher than that in milling of the α-β type alloy. Measurement of cutting forces confirmed that in the case of the β type alloy the ratio of the principal cutting force to the thrust cutting force near the point of disengagement of the tool was much higher than that in the cutting process. The force of the principal direction near the point of disengagement was thought to be produced by strong adhesion to the flank face. Also, structure analysis using FEM revealed that the estimated shearing force of the adhesive was sufficient to break the flank face.

Using a binder-less PcBN tool, improvement of processing efficiency was tried in machining of a vanadium-free titanium alloy, Ti-6Al-2Nb-1Ta which was recently applied for a surgical implant material. The tool which is prepared through the direct conversion sintering of h-BN under both high pressure and temperature, exhibits an improved high thermal durability. It was confirmed that a binder-less PcBN tool exhibited lower flank wear and kept sharper cutting edge compared to the tools made of materials such as sintered carbide, conventional PcBN and polycrystalline diamond with Co-based binder, after turning in cutting speed of 4.2m/s, feed rate of 0.15mm/rev, depth of cut of 0.5mm under an application of a high pressure coolant. Also, milling tests were conducted with a radius end mill tool whose tip was made of the binder-less PcBN material. As a result, the possibility of high speed milling at cutting speed of 8.3m/s was found.

A new method of numerically controlled ultra fine polishing for brittle material is proposed. In this method, the offset of the polisher to the designed profile is controlled to be constant in non-contact, and the feed rate of polisher is fixed instead of polishing load. In this report, the surface polishing characteristics of this method and the influence of the viscosity of polishing compound are examined theoretically and experimentally. The following results are obtained : (1) When the clearance between the polisher and the work surface exceeds the definite value, the machining action does not occur. (2) The flow rate of polishing compound at the gap between the polisher and the work surface, and the stock removal rate are independent of the viscosity of polishing compound. (3) Observations of surface textures with roughness tester and AFM indicate that the surface roughness of polished surface is improved with the increase of the viscosity of polishing compound.

Thin diamond blade is widely used for the precision slicing of electronic parts such as magnetic head. It is well known experientially that some properties of blade have a great influence on the machining characteristics of workpiece, i.e. the work damage and the blade wear.ln order to understand the relation between the properties of blade and the machining characteristics, the mechanical properties of thin diamond blade are investigated in detail through the measurements of the tensile strength, the dynamic visco-elasticity and the wear resistance of bonding material. It is found from the experiments that there are notable differences in the mechanical properties of various blades.