| Arithmetic Average Roughness (Ra) | The arithmetic average height of roughness component irregularities from the mean line measured within the sample length (L). This measurement conforms to ANSI/ASME B46.1 "Surface Texture - Surface Roughness, Waviness and Lay". Ra (formerly known as AA or Arithmetic Average in the U.S., and CLA Centerline Average in the U.K.) is usually expressed in microinches (µin), and performed by moving a stylus or profilometer in a straight line along the surface. A consistent and measurable surface finish can be specified for a desired roughness i.e., 9-11 microinch. |
