Ambiguities in the definition of spacing parameters for surface-texture characterization

A range of instruments is available for surface-texture measurement. The instruments record the ( x , z ) coordinates of data points that represent a surface profile, and apply software to filter the data and compute various surface-texture parameters that aim to describe the properties of the surface. However, many current and proposed parameters are not unambiguously defined. The focus of this paper is on one such parameter, namely, the spacing parameter RSm . It is shown that the definition of the RSm parameter given in standards is ambiguous, leading to the possibility of different algorithms for calculating RSm whose implementations can give results that differ considerably. Results obtained from three algorithms for calculating RSm applied to a real measurement data set are presented.