Stylus X Ra/Stylus Y Ra
The various Stylus X/Stylus Y ratios are found by dividing the corresponding Stylus X parameter (e.g., Stylus X Ra) by the corresponding Stylus Y Parameter (e.g., Stylus Y Ra). Thus the various ratios are unitless quantities.
A lathe- turned surface (A) for which Stylus X Ra/Stylus Y Ra is about 2.5 and a peened surface (B) where Stylus X λq/Stylus Y λq is about 1.0.
The ratio of the various Stylus X and Stylus Y parameters demonstrates the spatial isotropy of the surface texture. For example, the lathe-turned surface (Figure A) has a high degree of anisotropy and thus the ratio of Stylus X Ra/Stylus Y Ra is greater than 1.00. A shot peened isotropic surface will tend to have Stylus X and Y ratios of about 1.00. The ratios may be used to assess the ability for a given surface finishing operation to remove remnants of a previous operation. The ratios may also be used to uncover any dominant surface directional paths that may contribute to fluid leakage.