There is no specific answer for this question. The reason is that any grade
of paper contains a range of particle sizes both larger and smaller than the
stated grade.

The size distribution conforms to the usual bell-shaped curve. I don't have
any info on the width of the curve, but the FEPA grades(designated "P") have
a narrower range of particle sizes than the US standard, CAMI grades. FEPA
graded abrasives are becoming more and more common in the US.

There is also a difference in the grit size, for the same number, between
the two grading systems. Above 220 grit, the difference in grit size
becomes more pronounced as the numbers increase. For example, 320 = P400
and 600 = P1200 (approximately)

CAMI: Coated Abrasive Manufacturer's Institute (ANSI standard)
FEPA: Federation of European Producers of Abrasives

Randy


"Dave" wrote in message
oups.com...
Anyone know how different grades of wet/dry sandpaper relate to the
scratch depth they leave behind? I realize scratch depth must be very
material specific but my interest would be mostly 6061 aluminum and
mild steel. To phrase this question another way -- how much material
would have to be removed to mirror polish out the scratches from 400,
600, 800 grit? Thanks.