The measurement of a component’s surface texture may be described by many texture parameters. The question often arises: How many measurements do I need to make for a given parameter to obtain a particular level of confidence in the result? This article will give some basic guidelines for determining that number of measurements.

The many texture parameters are typically organized into categories. These include average height parameters such as roughness average, or Ra; extreme height parameters such as the maximum peak-to-valley, Rz; spatial parameters such as the mean profile spacing, Rsm; functional parameters such as the reduced peak height, Rpk; and hybrid parameters such as rms surface slope, Dq. A description of all the various texture parameters may be found in the standard ASME B46.1—“Surface texture (surface roughness, waviness, and lay.”

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