CNC Machining Surface Finish Guide: Ra Chart, As-Machined, Bead Blast, Anodize, and Chem Film

Engineering reference for specifying surface finish on CNC machined parts from Olympus Machining LLC, an ITAR-registered precision CNC machine shop in Hanover, Pennsylvania. Covers Ra (roughness average) values from 500 µin down to 4 µin with the machined surface finish chart, standard as-machined ranges (125 µin Ra baseline, 63 µin Ra with finish pass, 32 µin Ra for O-ring grooves and bearing fits), glass-bead and aluminum-oxide blasting (~0.0005 inch material removal, uniform matte cosmetic), Type II sulfuric anodize per MIL-A-8625 (0.0002–0.0010 inch buildup, Class 1 clear and Class 2 dyed), Type III hardcoat anodize (0.0010–0.0040 inch, 60–70 HRC equivalent, 50 percent growth into part), and chromate conversion chem film per MIL-DTL-5541 (under 0.0001 inch, electrically conductive, Type I hex-chrome and Type II trivalent). Tolerance impact table, cost multipliers vs as-machined baseline, DFM tips for masking threads and bores, and selection guidance for aerospace, defense, electronics, and medical CNC parts. CAGE 9V9P0, CMMC Level 1.