Very polished edges can be achieved with ultrafine white ceramics followed by stropping with green chromium polish. I routinely put this kind of edge on wood carving knives and gouges, but only because that kind of edge works best for push cutting in wood. The angle of the edge and blade geometry can also effect edge performance. The optimal edge depends on the knife, the steel, and the material to be cut.
I agree with those who prefer a slightly roughed up edge for a generl purpose knife. It will push cut well, and slices most materials better than a highly polished edge.
Once you get to the finer abrasives, sharpening technique is probably much more important than the exact abrasive grit being used. You should be able to maintain edges very well with only two stones, a 'medium' and a fine. You can add an ultrafine stone if you like. I like to strop all my knives, even if I only put a 'rough' edge on them. 'rough' for me is a medium ceramic stone.
If you do not let the edge deteriorate badly during use, you should not need to use the rougher stones except on the exceptionally dull knife, or to reprofile a knife with the thick and profile or asymetrical edge bevel angles.
The grit sizing for ceramics is different than Japanese water stones, or for diamond stones. I agree that comparing the average particle size in microns would help a lot, but as pointed out, some materials break down to smaller and smaller particles quickly.
Fine, and ultrafine diamond stones make a nice pair of stones, or medium and fine ceramics, or a 1000/4000 grit combo Japanese waterstone. They all work a little differently but will yield similar edges although the diamond stones will leave the roughest final edge. That is not necessarily a bad thing, a skinning knife will work best with a rougher edge.
I thick ceramics are the cleanest and easy to use stones to use. But I also like to play in the mud with waterstones sometimes.
I have not yet used diamond stones on my knives, but many here really seem to like the DMT products. The word in woodcarving circles is that these cut too fast, and leave a relatively coarse edge (bad for carving) compared to ceramics or waterstones. I have seen a graph produced by Norton which claims to 1200 grit diamond stone is the equivalent of a 6000-8000 grit waterstone in final polish, and cuts much faster. I think there is something VERY wrong with that chart.What I find strange is that folks who really do need ultra high polished edges do not seem to use the diamond stones very much. I think Beam is right about the fine stone being rougher than a fine ceramic, or maybe even a 1000 grit waterstone.
BTW, shaving and paper cutting is only the Beginning of getting a nice edge.
A gratuitous appeal for more gadget-less sharpening:
I really think learning to sharpen freehand will teach folks much more about how to sharpen than using angle fixing systems like Edgepro, or V-sharpeners. I took me a year of daily effort before I started to be able to properly sharpen my woodcarving tools. What used to take hours can now be accomplished in a few moments. It takes a while to learn, and can be very frustrating a first, but once you 'get it', you will be able to put great edges on almost any knife with any kind of stones.
As with many skills, having the 'best' tools is much less important than having the knowlege and experience to use the tools you have well.
Paracelsus
[This message has been edited by Paracelsus (edited 05-12-2001).]
