Preselection Of Diamond Single-Point Tools

Diamond single-point tools of the very highest quality are required for precision machining of optical surfaces. However, a great variation in edge quality and tool life is observed in practice. The differences between poor and excellent tools are subtle and not easily detectable without verification by actual machining. A companion paper concerning the tribologic aspects of tool-edge quality and life discusses the possible mechanisms of tool degradation. This paper provides a discussion of practical methods for preselecting tools for high performance without resorting to machining use. Edge quality as observed by optical microscopy is not sufficient. Scanning electron microscopy and a recently developed two-stage replication process for the cutting edge and subsequent examination in transmission electron microscopy can yield the necessary resolution (<< 100 Å). In addition to characterization by high resolution microscopy, tool crystallographic orientation and perfection are also crucial. X-ray diffraction characterization is described in detail.