Superfinishing uses fine grit sized materials to achieve the desired finish.
The sizing of abrasive grains is determined by organizations such as the Federation of European Abrasive Products (FEPA), and the Japanese Industrial Standards Committee (JIS). Most superfinishing processes use conventional abrasives with grit sizes between 400 and 1200 grit on the FEPA scale. Some applications, such as miniature bearings, may require the use of sub-micron sized particles. Generally, the use of finer grit sizes will improve surface finishes. The table shown in this paragraph compares the nominal grain sizes of conventional abrasive particles using the FEPA and JIS standards.
Grain Sizes
| FEPA | JIS | Micron |
|---|---|---|
| 320 | 500 | 35 |
| 400 | 700 | 23 |
| 500 | 1000 | 18 |
| 600 | 1200 | 14 |
| 800 | 2000 | 8 |
| 1000 | 3000 | 5 |
| 1200 | 4000 | 3 |
| 1500 | 6000 | 1 |
Superabrasive applications which require heavier stock removal utilize larger grit sized abrasive grains. The sizing of larger abrasive grains is also determined by international standards organizations, and the table below shows a comparison of FEPA, mesh, and micron sizing for some common larger abrasive grains.
Grain Sizes
| FEPA | Mesh | Micron |
|---|---|---|
| D426 | 40/50 | 426 µm |
| D356 | 45/50 | 356 µm |
| D301 | 50/60 | 301 µm |
| D251 | 60/70 | 251 µm |
| D213 | 70/80 | 213 µm |
| D181 | 80/100 | 181 µm |
| D151 | 100/120 | 151 µm |
| D126 | 120/140 | 126 µm |
| D107 | 140/170 | 107 µm |
| D91 | 170/200 | 91 µm |
| D76 | 200/230 | 76 µm |
| D64 | 230/270 | 64 µm |
| D54 | 270/325 | 54 µm |
| D46 | 325/400 | 46 µm |