Perceived and real roughness variations across machined surfaces

To measure and specify surface roughnesses, due consideration must be given to the observed parameter variations which can result (i) because of the measurement process itself, and (ii) genuinely from the inherent non–uniformity of surface texture due to the manufacturing process employed. In the current investigation, recommendations have evolved concerning how to reduce the apparent roughness variations, which can occur when using a Talysurf 4 stylus–based profile–tracing instrument. In addition, true local parameter variations, for a range of finishing processes, have been measured in order to indicate typical acceptable tolerances for roughness parameters.