Cutting edge radius of single-point cutting tool made of nano-polycrystalline diamond and phenomenon generated in ultraprecision cutting of oxygen-free copper

Abstract

An experiment was conducted to proove that a single-point cutting tool made of nano-polycrystalline diamond with a cutting edge radius of 0.3 nm can fabricate a cut face without damaged layer by decreasing the depth of cut. A face turning test of oxygen-free copper showed that an actual surface roughness of 2.4 nmRz which is close to the theoretical value of 2.0 nmRz could be achieved when the depth of cut and the feed rate were set at 0.2 μm and 2.5 μm/rev, respectively. In addition, it was observed that surfaces of the removed chip at a thin part of a free face were smooth and showed no lamellar waviness. The minimum thickness of cut, from which a comma shape chip was generated, was calculated from the measured chip width. This minimum thickness of cut was calculated to be 0.31 nm, which is equivalent to the lattice constant of copper. The kernel average misorientation map of the cut face obtained by electron beam backscatter diffraction clarified that almost no lattice defects were formed in crystal grains when the depth of cut was set at less than 1 nm. This means that the dislocated area generated in front of the cutting edge was negligibly small and the cut face without damaged layer could be fabricated.

Keywords

• ultraprecision cutting
• oxygen-free copper
• cutting edge radius
• uncut chip thickness
• damaged layer