Metal Polishing Specifications
The information provided below is somewhat subjective and is used as our general guide at Williams Metalfinishing. In 99% of the surface finishing situations we encounter, the aesthetic value dominates over the functional value.
#3 Finish - Grain finish. Also called Grinding, Roughing or Rough Grinding
Very coarse finish. The material is polished to a uniform finish between 60 and 180 grit.
#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 120 - 180 grit belt or wheel finish and then softened with an 80 - 120 grit greaseless compound or a medium non woven abrasive belt or pad.
#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 or wheel finish softened with 120 - 240 grit greaseless compound or a fine non woven abrasive belt or pad.
#6 Finish
Buffed finish. Some light grain. Some haze. This finish is produced by polishing with a 220 - 280 grit belt then buffed with a sisal to create a uniform buffed finish.
#7 Finish
Smooth buffed finish with a very bright appearance. Very 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. A #7 finish can be made bright by color buffing with coloring compound and a cotton buff. 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 finish with clear reflection - No haze. All surface defects are removed. The part is buffed and then color buffed to achieve a mirror finish. The quality of this finish is dependent on the quality of the metal being polished. Castings that have pits will be difficult - if not impossible polish to a #8.
Finish Cross Reference Chart
| Grit |
RA |
RMS |
Trizact |
| 30 |
|
250 |
|
| 40 |
|
200 |
|
| 60 |
145 |
150 |
|
| 80 |
71 |
125 |
|
| 100 |
61 |
69 |
|
| 120 |
52 |
58 |
A160 |
| 150 |
42 |
47 |
A130 |
| 180 |
30 |
34 |
A110 |
| 220 |
20 |
22 |
A90 |
| 240 |
15 |
17 |
A65 |
| 320 |
12 |
14 |
A45 |
| 500+ |
<3 |
<3 |
A35 |
| 1200 |
|
|
A20 |
| 1500 |
|
|
A10 |
|
