Help Needed: Finishing an Edge

The Burgh said:
You're yelling!

I have read that thread, and it seems to focus on the depth of the blade in the clamp. That's not in play here.

Sorry your self-evident expertise is just not making sense to me, nor is it showing up in my use of the KME.

Oh well, onward and upward.
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I am not aware that I am yelling nor is that my intention, I just want to help.

Here are two photos I just made. One front view and one side view that hopefully make more sense to you.

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Both show the same as cbwx34 showed in the other thread:

cbwx34 said:
When I first saw the Wicked Edge post a few years back, that the angle doesn't change, I thought, "that's crazy, of course it changes". It's basic trig that most learn... if the distance increases, the angle decreases in a triangle, right?

Long story short, after a bunch of testing, I ended up figuring out, that WE is right. As long as you're in the straight area of the blade, the angle won't change, no matter how far down you go. Take a look at these pictures...

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I figured the easiest way to prove WE wrong, was to take an extreme example. So, if you look in the top photo, I took a flat piece of aluminum and mounted it in the WE. Then I took dental floss and from the same point on the angle bar (20 deg I believe, it's been a few years), I attached it to points on the aluminum. If you look at the top photo, it seems obvious that the angle is getting smaller as you go down the "blade" right? But, if you put a stone on the arm, and held it as far out as you could, the relation between the aluminum and the stone didn't change... it still contacted the aluminum at the same angle.

That's when I realized that the angles you see in the top photo are not the angle that the stone is sharpening at. If you take a look at the lower photo... a picture taken sighting down the aluminum, you can see that all the pieces of dental floss line up perfectly. This is the angle the aluminum "sees", and what the stone sharpens at.

To answer the question about the Lansky directions, I think that no-one ever really looked at this before. It just seemed logical that the angle would change, as you move away from the pivot.

I also think that there is some observances that sharpeners mistake for the angle changing. One is, as a knife curve towards the tip, if it's far away from the pivot, the angle can change... this is shown in the WE post. So the assumption is made that it was probably changing the entire length. Another factor... many knives taper as the move toward the tip, even in the straight area you sometimes move into thicker metal, which can result in a wider bevel. So, the assumption is made that the angle changed, even though it's actually a change in the blade. Finally, many blades aren't straight, but have a slight curve, which can change the angle.

The easiest way to test this is to set aside what you think you know is true, like I did, get a long straight knife or even a piece of metal... rig up something that looks like a Lansky or WE, and test it out. When you figure this out, you'll realize that the best way to "set" a knife on a guided sharpener (Wicked Edge, Edge Pro, Lansky, etc.), is not by the length, but by the relationship of the curved area toward the tip. Makes sharpening a lot easier.

Hope this helps!
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Glad you are still here.

"Finally, many blades aren't straight, but have a slight curve, which can change the angle."

I think I see our dilemma: I have never sharpened a straight- bladed knife, and don't foresee that I ever will. They all have a rounded point. I'm is that point, the curvature that gives me fits and causes me to move the clamp along the blade.

On the straight portion of the blade, I don't move the clamp.

On many sharpened knives I see, even new ones, the grind on the curve, and especially the tip, is wider than the straights
 
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I think that a good rule of thumb would be for the curved part of the blade to follow the arc of the stones as much as possible. More or less the same as bflying is describing in the other thread.

Wicked Edge describes a way of finding the sweet spot with the use of a Sharpie here: https://www.wickededgeusa.com/finding-the-sweet-spot-positioning-your-knife-from-front-to-back/

With the KME I use a pen to find the best position and with the WE or Lansky, I use a piece of tape on the stones.

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From the WE description:
Even though the angle is remaining constant throughout the curve of the blade, you might experience a wider bevel toward the tip of the knife due to the way the knife is ground. As the belly of the blade curves toward the spine of the knife, the edge is often cut from thicker stock resulting in a wider bevel. An 1/8″ thick blade with a 22° per side angle will have much smaller bevels than a 1/4″ blade with the same 22° angles. On knives where the tip is inline with the spine and where there is not a distal taper, the effect is more pronounced. A wider bevel in this circumstance is a purely cosmetic concern since the angle is constant.

Hope this helps,

Frans
 
And so our journey comes to a successful end.

Special thanks to "fvdk" for patience, pictures, references and expertise!
 
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