On 30 Oct 2005 06:34:17 -0800, "Dave" wrote:

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.

Have a look at
http://www.cs.rochester.edu/u/roche/...rit.sizes.html

Looks like 800 grit has avg dia of .00048". Assuming that you got all
previous scratches out with the 800 grit, this would suggest that
you'd need to remove somewhere between .00024" and .00048" of material
to achieve a mirror polish.