Grit Sizes

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