Cutting force, grinding force and surface roughness of grinding are the most important parameters to scale machine progress, thus precision methods for them is needed in engineering.

Experiments indicate that the fractal scale, together with the fractal dimension can effectively reflect the fractal scale range of natural textures and the texture roughness within the scale range.

This paper discusses the similarity criteria of air flow model, the selection of scale, equipment and instrument, and the calibration of model roughness.