2004 年 70 巻 1 号 p. 106-111
Ultraprecision cutting tests were performed on single-crystal calcium fluoride. Effects of the tool rake angle, the cutting fluid type and the crystal orientation on brittle-ductile transition behaviors were experimentally investigated. It was found that two types of microfractures occurred in wet cutting; one occurred in high feed regions and the other appeared in very low feed regions. The boundary conditions for the occurrence of these microfractures were affected by the tool rake angle and the cutting fluid type. The microfractures occurring under the low feed conditions were due to the special thermal properties of the work material and could be avoided by dry cutting. In the dry cutting tests, the brittle-ductile transition boundary changed significantly with the crystal orientation. The minimum critical chip thickness for generating a uniformly smooth surface was 85nm.
