Answer: Rempco controls thread finish between 16 and 64 microinches Ra (0.41μm ≤ Ra ≤ 1.63 μm) depending on the application. Generally the rougher the surface the greater the wear, however, very smooth surfaces, less than 10 microinches (0.254 μm) Ra lack the ability to capture wear debris or hold lubricants. Refer to Threading Process Finishes for a comparison of the various ranges available.