Surface roughness is generally the degree of texture variability of a surface. In metrology, surface roughness measures the amount of bumps and dents, or peaks and valleys, across the surface of a part. These irregularities are to be expected on any machined surface provided the natural result of working with a range of tools to cut, shape, and build a part. The peaks and valleys, in other words the degree of surface roughness, are important in the eventual functionality of a part. Manufacturers will often measure surface roughness using a surface roughness gage or tester, and get a parameter in the form of Average Roughness (Ra) or Mean Roughness Depth (Rz). While these are the most common parameters used, other measures of surface roughness exist. Back to entire glossary
