surface roughness parameters:
Use the following formulas to convert average roughness (Ra) to other commonly used surface roughness parameters: R t = R a x 8.7 R z = R a x 7.2 R z ISO = R a x 7.6 R max = R a x 8.0 R p = R a x 3.6 RPM = R a x 2.9 RMS = R a x 1.1 The conversion formulas work regardless of whether R a is given in microinches (µin) or micrometers (µm). To convert metric R a to centerline average (CLA), use the following formula: CLA (µin) = R a (µm) x 40