Wicked Edge / Edge Pro

If it's not a parody then it is incorrect. First, the method used is very crude- the twine and cardboard are way too low-precision to be making any conclusions off of since the average person is going to have trouble seeing the difference between changes of even single degrees of angle. Even more bothersome is the image was taken smack dab in the middle of the box, not down the blade as it should have been.

I think the only way this will truly rest is if I show an example demonstrating exactly how much the angle will change using the exact dimensions of the W.E. and, say, a 14 inch straight edge knife.

The angle and bevel changes, and I'm surprised this idea is difficult to swallow for some :(.
 
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Twindog said:
Clay and Frank Hillary are correct. You can model this yourself with string and a box (don't need no stinkin' cad program).

The left side of the box represents the vertical position of the knife. The front right corner represents the axis of the stone. The string shows the angles for three different stone placements on a long blade. When you tilt the box and look down the angles, you can see they are all the same. No matter how far you go down a straight edge, the sharpening angle remains the same. It doesn't change until the blade starts to curve.


DSC01649.jpg

DSC01652.jpg
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A picture is worth a thousand words! There ya go. Some would have you believe that the angle changes (when using the Wicked Edge)
 
stitchawl said:
I tried it myself, and you're right! It's only the width of the bevel that changes due to the increased length of the guide arm/stone, not the sharpening angle! Who'd a'thunk it?!? :eek:
The 3D factor had me completely buffaloed! Thanks for show me the light!

Stitchawl
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If the width of the bevel changes, but the thickness of the blade is the same, then the angle is different.

The stone can rotate on the guide rod to match the edge, I think that is what Frank is saying. As you slide it along the length of the blade, like looking down it as in Twindog's picture, the stone can rotate to match the edge at the same angle, but where it contacts the edge will change. Starting in the vertical position, the edge and stone will be perpendicular and contacting wherever you hold it, let's say in the middle of the stone. As you slide the stone forward, it has to extend out on the guide rod, and also rotate on the rod to keep the same angle. But, the contact patch will change position on the face of the stone. Heck, you could turn the stone to be parallel to the edge and rotate it to where the face of the stone is at the same angle to the base as the edge is. But then, you couldn't sharpen the edge at all. At that point, the stone is pitched the same angle as the edge, but imagine at how low the angle is along the guide rod.

So yes, the stone can match the the edge at the same angle if you don't apply sharpening pressure. But when you apply force to the stone to reprofile, you aren't going to do it perpendicular to the edge, wiggling the stone up and down from the pivot of the rod, you are going to extend and retract it, where you are going to be changing the angle of the edge because you are moving the stone along the hypotenuse - the guide rod, instead of just letting it shift and rotate to follow the original edge angle. The hypotenuse there is different from the one that matches the edge.

You have two angles on two different planes, one perpendicular to the knife edge, and one that runs parallel to the length of the sharpening stone-the angle of the rod. They match when you lay the stone on the edge vertically, they don't when you push it out on the edge. It takes some extension to make them vary noticeably, I always figured people would adjust the position of the knife in the clamp before trying to sharpen at the furthest reach of the the guide rod. Like I said, I haven't seen anyone say they've changed the angle on the straight portion of their edge. I think that most people sharpen shorter blades on clamp systems and move longer blades on the edgepro so it isn't an issue for most.

All Twindog has to do is take a picture from above the box to show the other angle. The isometric shot shows it for the most part. Depending on how you move the stone, you will be sharpening at an angle somewhere between the two images. This is why it isn't an issue for most, I'd say.

2nknk1t.jpg
 
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BladeChemist said:
First, the method used is very crude- the twine and cardboard are way too low-precision to be making any conclusions off of since the average person is going to have trouble seeing the difference between changes of even single degrees of angle. Even more bothersome is the image was taken smack dab in the middle of the box, not down the blade as it should have been.
Click to expand...

Here's a photo for you....

WEAngle02a.jpg


This is 28" from the clamp. Kinda crude but the results are basically the same as the twine and box photo. I tried to site down the "blade" as you thought it should be.

Another interesting photo...

WEAngle03.jpg


The angle is set at 20 deg. This is as far out as I could get the stone, and keep it on the rod. As long as you keep contact between the entire edge of the blade and and stone, the angle stays essentially, at 20 deg. You could rotate the stone and sharpen at a different angle, but you can immediately tell because the two edge aren't totally in contact. And right now, there's not a bevel on the "knife" (it's not even a knife) for the stone to match. It lines up as long as there is 100% contact between where the edge of the knife, and the stone come together.

I gotta say... this thread has been a real eye opener for me.

cbw
 
Great pic cbw, I will try to show what I am talking about without looking too silly.

What matters is which way are you moving the stone to remove metal. The relative angles are a little off because the shot is not square with the base of the WE, but these are roughly the two directions you are dealing with. No one is going to sharpen in purely one direction or the other, so the angle isn't going to be thrown off much at all on the actual sharpening.

They are going to be close because the guide rod isn't 28 inches long:)

 
There is something that is undeniable: Pythagoras' theorem. Since Pythagoras discovered it in VI B.C. no one has been able to prove it wrong and WE or EP will not be the first ones.

However, I believe that the key element here is discovering what angle matters:

a) the actual angle between the axis of the stone and the mean plane of the blade or
b) the projection of the later angle on a plane perpendicular to the mean plane of the blade.

If we consider the angle described in a), it does change. It is mathematically so and it varies with distance only. Since b) is the projection of a) it does also change, but not at the same rate.

However, these changes are probably too small to have any real world difference. You can grab a calculator and do the math, but it will be rather time consuming and, IMO, a bit pointless.

As for the jig with the string, all that that photo proves is that the projection of the hypotenuse of the triangle, represented by the rope, on the plane perpendicular to mean plane of the blade remains constant. Indeed it does, but it is not that that we are interested in.

EDIT: Actually, the projection of the hypotenuse of the triangle also does change, but unless the distance from the pivot point is significant, it is nearly unperceivable.
 
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made a short video (should actually be a little longer but the camera stopped on me without me knowing :foot:) will upload it to explain my thoughts.

I wish I didn't sound like an 8 year old, I turn 34 in less than two weeks. I also wish I had worked from a script, it's not the best.

anyway, up soon
 
hardheart,

I've thought and experimented with this until my head hurt. :) Initially I thought the same thing as you... that the direction of the stone movement, or the angle of the rod, affected the angle. I thought Clay's diagram kinda proved it, because the angle he shows doesn't match the direction of anything.

But my thinking now is, that the stone angle you show, going up and down the rod isn't what's important.... what is important is that we're removing metal at an angle to the plane of the blade, which is straight up and down. If I could hold that stone in position, and remove the rod, I could move the stone in any direction (as long as I didn't rotate it), and I'd be 20 deg. to the knife. Or, to view it another way... rotate your monitor (or rotate the picture) until the stone is flat like it was laying on a table, and you have a flat stone with a knife resting on it at 20 degrees. Turns out, Clay's triangle is correct... no matter how far out you are... the angle that matters is between the plane of the blade (going straight down), and the plane of the stone in the same direction... which equals 20 deg. no matter how far out you go (that's what the "string" picture shows).

What's interesting is what I said before... it all lines up when the plane of the blade is 100% across the stone, regardless of how far away from the pivot you go. It becomes a bit confusing, because you could rotate the stone off this angle, (if the angle was small enough you could start scrubbing the side of the blade if you wanted), but you can tell right away if you do this. So the angle isn't matching what's already on the knife, it's set by the contact between the two at the edge.

So, while the angle changes as you go down the blade from the clamp out (it gets smaller, and I think this is what people think of as changing), what doesn't change is the angle between the blade and the stone looking down... it stays at 20 deg. (or whatever it's set at.) That's what laying it all out showed me anyway... and is not at all what I expected. Like someone said, it's very counterintuitive to what I thought was happening, or should happen.

cbw
 
Yeah, I'm really having trouble articulating it, but the issue isn't the sharpening angle as much as the way you can reshape the bevel/profile of the knife if you spent an inordinate amount of time at the full extension of the guide rod. Stitch's bevel got wider because if he had a grinder instead of a stone at the end of the guide rod, the blade would be reshaped with the belly turning up right there. The bevel got wider because more metal is being removed to reshape the blade, and by the time it's done, you'd have the same width bevel along a different curve. The angle changes until the metal getting in the way allows it to create that same radius again. The jigs aren't created with a certain blade profile in mind, there is still the movement in turning the stone, sliding along the guide rod, and arcing from the pivot to follow them. Changing the angle is at an extreme distance/angle relative to what we are dealing with. Like my earlier pic, if you sharpen with the stone at a funky angle you get a lopsided bevel until you wear away the metal at the far side of the stone, but who is going to hog metal with the stone at that angle and distance? Also, most of the sharpening is done with the stone at a slight angle from perpendicular to the edge, and nearly none of it if you move the blade and overlap strokes. The metal removal is going to be working to create an edge perpendicular to the length of the stone, or closer to that direction, for most of the stroke. As the stone turns, you aren't applying pressure purely along that direction and you will be scratching more toward a lengthwise path on the edge. But if the blade is long enough, or the curve different enough, you can't remove metal in exactly the same way as the knife is ground using the mechanics we generally do.

It isn't so much that the clamp and rod sharpener can alter the sharpening angle, it's that it takes some particular motions to do it and you would need to push the dimensions of the device to an impractical level for those actions to matter, at least with the speed of metal removal we're dealing with. You can round over the edge with one of these devices, but who does that?
 
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How do both do at keeping a nice pointy tip?
 
I don't really understand what you're saying hardheart... i'll wait for your video.

What becomes quickly obvious in all this, and this isn't specific to the WE, is how fast the angle can change as you go around a curve toward the tip, and how many more factors quickly come into play. Maybe it should be taught to "sharpie" the bevel toward the tip, and set the knife based more on that? Even sharpening freehand could benefit from this.

rycen, there's no issues with keeping a tip on either system.

cbw
 
video was so crappy that I took pics instead

here's a cardboard model with a curve in the edge. Three strings line up because they are on the straight section.










Here at a couple positions the angle is the same because we can present the sharpening surface of the stone at the same angle, the direction of travel just changes.




But in the curve, the stone rotates, and the sharpening surface is no longer on the same plane. Since the edge reduces in height, the sharpening angle changes. One leg of the right triangle will remain constant, that is the distance from the center of the clamp to the pivot point of the guide rod. Another leg can remain constant in that if the edge remains straight and level, the distance from the base to the edge will be constant. That is the view that lines up the strings taped at different angles at the same height. But when you change the height, the stone will not present itself to the edge at the same angle. So the sharpening angle changes in the curve.
 
I think CBWX's string photos really clear things up. They show just where my own thinking went wrong. The upper photo was how my mind was seeing things, and it's clear that the angle to the blade changes dramatically as the distance of the hypotenuse increases. But that's not the sharpening angle, and it's where I was making my mistake. The second photo clearly shows that sharpening angle, and that doesn't change with the distance, as it's on a completely different plane. No question that the bevels change though. That can be seen just from the results of the sharpening!

EDIT: I should have said ; 'on a straight bladed knife. That belly curve really changes things! LOL!

Stitchawl
 
What I was fumbling about saying was that with repeated sharpening or heavy reprofiling, you change the height then as well. If you clamp the blade lower in the device, you aren't sharpening at the same angle as if you would attach the clamp as close to the spine as you could. By the same token, if you wear the blade down, the angle settings are not going to give you the same measured edge.





But when you wear down the blade at the far reach of the rod, you do it at an angle, cutting a curve into the blade because you are moving the stone in an arc. Pretty much what I am saying is that if you burn up a sharpening stone carving a new belly into your knife at the 20 degree setting, it won't be 20 degrees because the angle in the curve doesn't match the one scribed on the machine.



That isn't going to cut an even bevel straight down because we are presenting the stone at an angle. This is why the bevel will widen on the way out from the center, and why you will change the curvature of a blade if you sharpen the wrong way for a long time. The stone will cut at an angle, then rotate around the bevel as it builds the curve. But this is a ridiculous amount of grinding at a really silly position.

More or less, you can defeat the angle setting of the device if you try, but otherwise the pics by others demonstrate that it holds within a half degree. It will not be absolutely perfect, and you will not instantly alter all of your bevels.
 
I'm working on the math behind the edge angle and bevel change. The fact that some of you are accepting that the bevel changes yet the angle does not is confusing me. Consider a much more simple example: imagine the cross section of straight blade of uniform thickness. Since we're creating a v-grind with the W.E. you need to ask yourself how the bevel can change without the resulting angle changing. Draw some cross sections. The edge bevel begins at the edge and follows a straight line to exit the blade. If it gets larger it has to decrease the sharpening angle. I believe the cardboard+string examples shown above are probably giving the illusion of a constant angle, but I'll post later with a more thorough writeup. Anyone else's thoughts?

Edit: or, just as fockewul explained (especially the part about not bothering to do the calculations ;) )
 
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It isn't just a matter of simple math, because the two angles are on two planes, and the degree of bevel change is going to be influenced on your particular sharpening motion and application of force. With the ability to rotate the stone about the guide rod, this just compounds the issue.

You can present the face of the stone to the edge at the same angle (sight down the edge and line up strings), but that doesn't mean you will sharpen at that angle. Also, you will change the angle of the centerline of the stone to the face of the blade as you run it out on the rod (look from the top), but you won't sharpen at exactly that angle either. We neither move purely up and down nor straight in and out when sharpening on these systems, so one angle does not completely overwhelm the other.
 
I agree with you there: it's not simple math :p.

As for sharpening motion and pressure, it shouldn't make a huge difference assuming the person using the machine stays consistent and hones their skills, and the ability to rotate the stones won't have any effect on the edge if you know what you're doing. These factors are much the same on the E.P.

Although- are you getting at the fact that since different areas of (a straight blade) will require different amounts of metal to be removed due to the bevel change, the blade may develop unusual wear patterns upon further sharpening? I wonder about that.
 
hardheart said:
It isn't just a matter of simple math, because the two angles are on two planes, and the degree of bevel change is going to be influenced on your particular sharpening motion and application of force. With the ability to rotate the stone about the guide rod, this just compounds the issue.
Click to expand...

I believe you made an important point. So far, we haven't taken into account the fact that we rotate the stone about the guide rod. If it wasn't so, we would be sharpening with a single contact point between stone and blade, expect when sharpening in a perfectly perpendicular position. We all know it isn't so. So, the math is time consuming and not easy. As I said before, it is not worth bothering.

Having said this, I conclude the following: sharp the way you like best! :D

Seriously, we are never going to get a definitive answer and it really doesn't matter that much. As long as you are happy with the results, keep sharpening that way. If you want a constant bevel width, get an EP and pull and rotate the blade as you sharp and you will get that result. If you like the way the WE works, by all means get one and have fun! :)
 
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