Grit Grading:
There are 2 basic ways of grading abrasion levels, CAMI and FEPA. CAMI is what has been used in the United States for many years. CAMI is an association of American Abrasive Manufacturers: Coated Abrasives Manufacturers’ Institute. FEPA is basically a newer standard used by European manufacturers, including Mirka, the inventor and manufacturer of Abralon, Abranet and associated abrasives. FEPA is an equivalent organization: Federation of European Producers of Abrasives.
The FEPA standard actually produces/requires a more consistent sized abrasive within any one specific grit level. The sizes of the abrasives in any one grit, meeting FEPA standards, fall with a narrower range of minimum and maximum for any one grit level.
Most American manufacturers have already begun to make their abrasives under the FEPA standard. So when looking for items, like sandpaper, be sure to check what the number printed on each piece of sandpaper represents before purchasing.
Grit Numbers:
Normally, the grit number is a 2, 3, or 4 digit number representing the abrasion/roughness level of the abrasive on the material (paper, cloth, woven nylon, pads, etc). We are used to seeing numbers like 100, 150, 180, 220 grit for woodworking and numbers like, 320, 400, 600, 800 and 1000 grit for bowling specific needs. These have been CAMI graded or US grit numbers.
To separate CAMI standards from FEPA standards, abrasives graded via the FEPA standard have the number preceded by the letter, “Pâ€. So if you buy new wet/dry sandpaper made in the US, you are likely to see “P600†or “P800†grit on the back, not just “600†or “800†grit.
Scotch-Brite nylon pads come in CAMI grades.
Abralon, being made in Europe, uses the FEPA grades. Their numbers are basically 2x what the equivalent US grit level is. For instance, the common Abralon pads are 500 grit FEPA, 1000 grit FEPA, 2000 grit FEPA and 4000 grit FEPA. These are equivalent to 360 grit US, 550 grit US, 1000 grit US and 2000 grit US.
Scotch-Brite nylon pads usually come in these levels (specific to bowling. There are others.):
maroon - 320 grit US,
green - 600 grit US,
light grey - 800 grit US,
blue - 1000 grit US.
(There is a 2000 grit gold one.)
(The grit level equivalency was obtained directly from 3M, the manufacturer of Scotch Brite pads.)
Abralon comes in 500 grit FEPA, 1000 grit FEPA, 2000 grit FEPA, and 4000 grit FEPA.
Valentino also distributes a set of pads similar to but different from Abralon in several ways. Their pads also come in FEPA grades, from P320 to P4000 grit, including some not available form Abralon (P600, P800, P1500, P3000 grits). According to Valentino, theirs differ from Abralon in this way (using their own words): “Our pads use a woven silicon carbide fiber unlike the abrasive mesh, this will allow for even consistent results and finer sand lines. Anything above 800 grit, you'll hardly see the sanding lines. With testing, the pads last 2 to 3 times longer, depending on how long you sand the surface of the ball. So if you can get 4 balls with the competitions pad you'll expect to get 10 to 12 balls out of our pad. Just depends on how you like the sand (2, 4, 6 sides).â€
There are several charts available online that show CAMI to FEPA and other grading levels:
http://www.taunton.com/finewoodworking/pages/w00006_sb2.asphttp://www.mirka-usa.com/downloads/pdf_files/grit_chart.pdfhttp://www.buffpolishgrind.com/pdf/gritcomps.pdf--------------------
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