I started sharpening knives professionally about 1982. I learned on a Baldor ¼ HP 1720 RPM grinder with 150 grit composite wheel from Gerber Legendary Blades. I sharpened into the oncoming wheel and then deburred the blade on a hard felt wheel with a jewelers rouge compound (you NEVER deburred into the oncoming wheel)!
Later I learned to use a 1” belt sander, just like Kershaw uses in their factory (I have seen them do it).
Now days I use a 150 ceramic belt and then I deburr with a leather wheel with white jewelers rouge. I can sharpen anything from a tiny penknife blade to a lawnmower or planer blade.
The two critical things are 1- constant angle; for me this is muscle memory- doing it so many that I don’t have to think about the angle. The second critical thing 2- is when using the belt…….move at a constant fast speed even while changing the angle of a curved blade in relationship to the belt, in order to keep a constant angle on the blade. Go too slow, you WILL burn a blade on a belt sander!
Now days I do 90% - 95% of the knives I sharpen on the belt sander. If I need to reshape a blade and remove a lot of metal from a small area, I use a slow wheel that travels through a water bath to keep the blade cool.
Now, I don’t recommend everyone go buy a belt sander to sharpen their knives, Not a good idea! But, if you use any system for 30 years, you should be fairly good at it.
All that being said (not to put down you fellows who are having problems with the D-2), I STILL have an off day when I cannot sharpen a Popsicle stick!
On those days I turn off the belt sander and wait until the next day when I can hold a consistent angle. If I let a knife stump me, or get in my head, I can’t ever sharpen it. So I wait until the next day when I am fresh and I can hold a decent angle and I start over.
There are certain knives I have had difficulty sharpening, but it is usually an angle issue (me not using the manufacturer’s angle
) & not a steel issue.
Not sure if this helps you or not, but as long as I have been doing sharpening (30 years) and doing it professionally I still have a bad day now & again.