Contributed by the Manufacturing Engineering Division for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received January 26, 2004; revised July 20, 2004. Associate Editor: M. A. Davies.

Thermal matching of coating-tool materials to optimize dry machining of steels is an interesting idea. Grezesik et al. find that the thermal properties of the materials involved, namely, the thermal diffusivity and the thermal conductivity, control the thermal and tribological behavior outputs of the machining process. Such a finding has been detailed in the discussor’s own work when studying dry sliding of metallic contacts 1,2, however, the physical interpretation of the contact parameter $b$ in the manuscript is not apparent.

The parameter $b$ is originally given by: $b=KρC1/2$ where $K$ is the thermal conductivity, ρ is the mass density, and $C$ is the specific heat. In this form, the...

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