SENIOR EDITOR An easy way to convert metric surface call outs to standard U.S. ones (rms) is to mentally multiply the metric value by 40. For example, 1.6 = 63 rms, 3.2 = 125 rms, and 6.3 = 250 rms.

S. C. Ammula, Y. B. Guo, Surface Integrity of Al 7050-T7451 and Al 6061-T651 Induced by High Speed Milling, SAE Transactions, Vol. 114, Section 1: JOURNAL OF AEROSPACE (2005), pp. 1135-1143 ...