Surface roughness refers to the small spacing of the machining surface and the unevenness of the tiny peaks and valleys. The distance(wave distance) between its two peaks or two wave valleys is small(below 1mm) and it is a microscopic geometric shape error. The smaller the surface roughness, the smoother the surface.
Surface roughness is generally formed by the adopted processing methods and other factors, such as friction between the surface of the tool and the part during the processing, plastic deformation of the surface layer metal when the chip is separated, and high-frequency vibration in the process system. Due to the different processing methods and workpiece materials, there are differences in the depth, density, shape and texture of the processed surface.
Surface roughness is closely related to mechanical parts, wear resistance, fatigue strength, contact stiffness, vibration and noise, and has an important influence on the service life and reliability of mechanical products.