| SURFACE FINISH COMPARISON CHART | |||||||||||||
| RA is the arithmetic average deviation of the surface valleys and peaks and is often used to specify the roughness of a machined surface. RMS is the root mean square average of the profile height deviations from the mean line of the surface and is mostly used for optical surfaces. | |||||||||||||
| The term Micro means millionth. So 1 micrometer is 1 millionth of a meter, or .000001 meter. Likewise 1 microinch is 1 millionth of an inch, or .000001". The term "Micron" refers to 1 millionth of a meter, which is also equivalent to 1 thousanth of a millimeter (.001 mm), and is represented by the greek symbol μ. Ra microinch ( μ" ) is basically the same as the CLA scale, or centerline average. | |||||||||||||
| Some Useful Conversions: | |||||||||||||
| Inch = " or in | 1 microinch (μ") = 0.0254 micrometers (or microns) | ||||||||||||
| Micron = µ | 1 microinch (μ") = 0.0000254mm | ||||||||||||
| Micro Inch = µ" | 0.001" = 0.0254mm | ||||||||||||
| Micrometer = µm | |||||||||||||
| Millimeter = mm | |||||||||||||
| Below are equivalent values on various surface measurment scales, and the manufacturing methods capable of producing these finishes. | |||||||||||||
| New ISO scale numbers | 1. | 2. | 3. | 4. | 5. | 6. | 7. | 8. | 9. | 10. | 11. | 12. | |
| RMS Microinches ( μ" ) | 0.5 | 1.1 | 2.2 | 4.4 | 8.8 | 17.6 | 35.2 | 64.3 | 137.5 | 275 | 550 | 1100 | 2200 |
| RMS Micrometers ( μ m ) | 0.013 | 0.027 | 0.055 | 0.11 | 0.22 | .44 | .88 | 1.6 | 3.44 | 6.88 | 13.75 | 27.5 | 55 |
| CLA or Ra microinch ( μ" ) | 0.5 | 1 | 2 | 4 | 8 | 16 | 32 | 63 | 125 | 250 | 500 | 1000 | 2000 |
| Ra micrometer ( μ m ) | 0.012 | 0.03 | 0.05 | 0.1 | 0.2 | 0.4 | 0.8 | 1.6 | 3.2 | 6.3 | 12.5 | 25 | 50 |
| Sand Casting | |||||||||||||
| Hot Rolling | |||||||||||||
| Forging | |||||||||||||
| Permanent-Mold Casting | |||||||||||||
| Investment Casting | |||||||||||||
| Extruding | |||||||||||||
| Cold Rolling | |||||||||||||
| Diecasting | |||||||||||||
| Flame Cutting | |||||||||||||
| Sawing | |||||||||||||
| Planing | |||||||||||||
| Drilling | |||||||||||||
| EDM | |||||||||||||
| Milling | |||||||||||||
| Laser Cutting | |||||||||||||
| Reaming | |||||||||||||
| Broaching | |||||||||||||
| Turning and Boring | |||||||||||||
| Tumbling | |||||||||||||
| Roller Burnishing | |||||||||||||
| Grinding | |||||||||||||
| Honing | |||||||||||||
| Electro-Polishing | |||||||||||||
| Polishing | |||||||||||||
| Lapping | |||||||||||||
| Superfinishing | |||||||||||||
