What is Ra and how does it relate to finishes?
Ra is an industry recognized measure of the roughness of the surface of polished material. Using an instrument called a profilometer, the peaks and valleys of closely spaced irregularities in the surface of the material are measured. The average of these measurements result in an Ra reading. Generally, the lower the Ra reading, the smoother the surface; and the higher the Ra reading the rougher the surface. Using developed “recipes”, where parameters such as belt type, belt grit, speed and pressure are carefully controlled, SMP can achieve consistent results for both standard and custom finishes.
For more detailed information or questions related to SMP’s coil polishing process, please contact one of our customer service professionals.
Also, you are welcome to arrange a visit to SMP to view all of our coil, sheet, plate and slab processing capabilities.