Over-Sharpening

[KnifeGrinders]

...
Mr. KG: Thank you for explaining the theory, I know one of the postings I read about this was yours, so I'm glad to have your thoughts on this.  I *think* I follow your reasoning, but perhaps my next question will determine whether I really do.  When I sharpen knives, once I'm past the coarsest stones, I alternate sides on every stroke.  My assumption is that at any given grit the burr created is about the smallest possible, and that I'm always then sharpening to your green line, regardless of how many strokes I take. Do you concur, or am I missing the point?
...

Your are right when grind on both sides of the edge is symmetric.
Keeping to our promise to the customers of sharpness under 100 BESS for mainstream knives, and <=50 for high-end, I've noticed that I cannot get under 100 BESS when the edge apex is not centered in the jig.

Below is an oversimplified modelling of what is happening during sharpening.
The first picture is for an ideally centered edge and even grind on each side, where you get the ultimate sharpness


1 - the burr is raised by grinding one side, at this stage you even out the bevel
2 - you start grinding the other side and evening out the bevel
3 - the burr is raised on the other side
4 - you minimise the burr by alternating sides and grinding with minimal pressure
Then deburr


The next picture shows an asymmetric grind - you eventually get a less sharp thicker edge.
This happens every time when you overgrind one side and/or where the edge is not centered in the jig, resulting in bevels of uneven height.
You may overgrind one side when you apply a little more pressure, or spend more time on that side.



I hear all the time that "The trick is to just keep flipping the blade so that newly formed burr is ground off as you go so as not to create some big gnarly burr that is difficult to remove."
In real life you have to even out the bevel on each side before you can work on the edge as such, and in the process lots of metal gets not only ground off but also shifted from side to side - and this is when the undesired asymmetry comes into play.