Specifying Surface Finish

To meet the increasing demands put on load bearing surfaces, design engineers are developing more rigorous surface finish specifications. It has been widely acknowledged that Ra alone is not adequate to specify critical load bearing surfaces. A lack of understanding of the more advanced parameters has resulted in designers selecting parameters that are redundant and assigning values that may not be achievable in production. Armed with a basic understanding of the parameters, a few little known relationships, and standard statistical tools, a designer can develop efficient and achievable surface finish specifications using advanced parameters such as the Rk family of parameters. Author: Michael A. Stewart, Numerical Engineering Research and Design, Holland, MI.