The information provided below is somewhat subjective and is used as our general guide at Williams Metalfinishing.
#4 Non-Directional Angel Hair
#4 Architectural Finish – Also called Brushed, Directional or Satin Finish
A #4 Architectural Finish is characterized by fine polishing grit lines that are uniform and directional in appearance. It is produced by polishing the metal with a 80- 180 grit belt or wheel finish. (65 RA – 30 RA)
#4 Dairy or Sanitary Finish
This finish is commonly used for the medical and food industry – almost exclusively used on stainless steel. Great care should be taken in removing the surface defects in the metal – like pits – that could allow bacteria to grow. This finish is produced by polishing with a 180 – 240 grit belt. (30 RA – 20 RA)
#6 Finish
Fine grain. This finish is produced by polishing with a 180 – 280 grit belt. (20 RA – 12 RA)
#7 Finish
Smooth buffed finish with a very bright appearance. Light haze. The part is belt polished with a 280 – 320 belt then buffed with a cut and color compound. This is a common finish in preparation for chrome plating, powder coating, anodizing, etc. This is a good way to keep polishing costs down when a part needs to be shiny but not flawless.
#8 Mirror Finish
“Mirror” bright finishes with clear reflection – Very light haze. All surface defects are removed. The part is buffed and then color buffed to achieve a mirror finish. The quality of this finish can depend on the quality of the metal being polished. Castings that have pits will be difficult – if not impossible polish to a #8.
True #8 Mirror Finish
No haze.
Finish Cross Reference Chart
| Grit | RA | RMS |
|---|---|---|
| 30 | 250 | |
| 40 | 200 | |
| 60 | 145 | 150 |
| 80 | 71 | 125 |
| 100 | 61 | 69 |
| 120 | 52 | 58 |
| 150 | 42 | 47 |
| 180 | 30 | 34 |
| 220 | 20 | 22 |
| 240 | 15 | 17 |
| 320 | 12 | 14 |
| 500+ | <3 | <3 |
| 1200 | ||
| 1500 |
