I am separating this from the last post to keep different subjects separate.
Here is how I sharpen a very sharp knife:
First, I take the bevels to 400 grit, sometimes higher. The edge is nearly sharp. All I can see if looked straight down the edge under a strong light is a glint on the flat area. It is about .005" at that point. For reference, a business card is about .010". I finish the bevel sanding usually by giving it a satin finish with a medium or fine Scotch-brite belt. I then draw the edge flat across a piece of 400 grit sandpaper to make sure the edge is smooth, flat, and even. An edge that has been ground on a belt grinder has a tiny "lip" that rolls over from each side ( similar to the wire in sharpening). This can make the edge appear to be thinner than it actually is. It also may wave up and down or side to side a bit. Look closely, with a magnifier hood if you have one, and check that the edge looks like a very thin, flat, straight line. If it gets wider and thinner when examined, the bevels are not evenly ground.
Get the pre-edge right before moving on the actual sharpening!
Now, to make that thin flat into as close as a zero edge as possible*.
I put a new 400 grit belt on the grinder, and slow it down to about 100 SFPM. I use a new belt because a worn belt will build much more friction. It is a common mistake to think a worn belt is good for sharpening, and acts like a finer grit. I just burnishes the steel more, but actually is a coarser belt than a new one. If you want a finer grind, use a finer NEW belt. Some folks use a 600 or 800 grit belt. I would hit it once on the 400 grit belt first if you are going that fine. This will keep the fine belt sharper longer.
I keep the blade moving at all times, and only hit each side once or twice.
I then sight down the blade under a strong light to see if there are any flat spots left. They will show up as glistening areas. I usually already know that they are not there, because I watch the wire form as the blade edge gets ground. If there is a flat spot, there won't be a wire there. If needed, I hit the edge another time or two. If the edge needs more than this, I did not get the edge evenly thinned out in the bevel grinding, and usually go back and touch up the bevel.
Once the edge is ground and there are no visible flat spots, the blade may feel dull if you try to cut with it, or "feel" the edge. Don't let appearances fool you. Under a rolled over microns of steel swarf lies a very sharp edge. A couple stropping strokes down a charged 3" strip of leather glued to a board will remove this "Wire" edge. I charge the strops with a variety of things from red rouge , to Flitz, to 50,000 girt diamond paste ( about 1/2 micron particle size). It somewhat depends on the blade and the steel, but it probably does not really matter...as long as it is a very fine grit compound.
After the stropping, I cut up postcards. I have the luxury of having available a nearly inexhaustible supply of 5X3" heavy stock, glossy flyer cards from the various sales and promotions our store runs. The vendors send them to us in thousands, and we only use 1/2 of what they send. These are just right in hardness and size to do cutting tests on. I make six to eight angular cuts on the card. It should slice cleanly into 1/4" wide strips. If I feel a catch, or a dull spot, I double check the edge with a magnifier hood on. That will tell me if I have a little wire left on or a dull spot I haven't sharpened enough. Dull is a relative term here, as these blade when "dull" will still cut you to the bone. Usually a few more slow strops takes care of the problem. If not, it gets set aside to re-do the edge on the 400 grit belt.
* It is impossible to take a blade edge to a "0" apex. The grain size and carbide size limit this, as well as the nature of the steel grains to pull away in sharpening. How close you get to "0" is a product of the steel type and the HT. The better you sharpen, the closer you come....but you will never get a true zero edge. On most knives, a microscopic serrated edge will cut better and last longer. There are many factors that make a blade cut better under different circumstances. This is an entire subject unto itself, which we will leave for another day. Roman Landes has made his career mainly on this subject alone.
