Edge geometry on a wicked edge (we130)

[brasileiro]

If you mean me... I wasn't offended, and you didn't do anything wrong. This comes up all the time. It's so counterintuitive to the way it seems it should be. If you read my post in one of the other threads... I was the same way when I first heard that "the angle didn't change"... that's why I stuck like a 3 ft. long ruler in the W.E... to prove it did. Which of course it didn't.

This round seemed to have quickly settled... maybe all those Photobucket pictures that disappeared... were just confusing people.

With anyone. English isn’t my native language. So, some words I have to go to google and on the exciting to write something maybe I had wrote something wrong and offensive. That is the reason I edit my posts, many of them is to try to make it understandable.
Also has the spell checker that sometimes puts some words not as they should be.

 

[Sergeua]

I'm going to mess with ya all and say as you grind your edge away the angle is slightly changing still as the hone lowers itself. You know like grinding your roof away. The top point is fixed but the roof is getting ground down. Its negligible stuff, maybe noticed if you reprofile something thick. Your angle cube might show thicker angle afterwards. Consistency is what's important with guided system, so yeah probably doesn't matter, but it's a theory.

 

[LarryT]

Wow I sure did open up a can of worms but I’m enjoying reading everyone’s input. Thanks to all.

 

[jalapeno]

Hi Larry, I guess I'm partly responsible for taking the worms out of the can, so I apologize for that. Getting back to your original question, I found this pic of a zt0450:

Given the spine of this knife, it looks like that might be a little challenging to clamp well in the WE, especially if you have the pre-2017 jaws. How stable was the clamping in the WE? Did it move at all while you were grinding? Did the edge have the thin/thick/thin before you started, or did your sharpening create that?

 

[LarryT]

Hi Larry, I guess I'm partly responsible for taking the worms out of the can, so I apologize for that. Getting back to your original question, I found this pic of a zt0450:

Given the spine of this knife, it looks like that might be a little challenging to clamp well in the WE, especially if you have the pre-2017 jaws. How stable was the clamping in the WE? Did it move at all while you were grinding? Did the edge have the thin/thick/thin before you started, or did your sharpening create that?

Actually got it to clamp very securely but I had to clamp it back near the handle more than I would of liked to. Wouldn’t it be better to try and have it centered in the vice?

 

[Officer's Match]

Actually that might be the best place for it (rearward) so the curved tip stays at a similar bevel. BTW, I just scored a WE130 for myself - now the wait for arrival.

 

[LarryT]

Actually that might be the best place for it (rearward) so the curved tip stays at a similar bevel. BTW, I just scored a WE130 for myself - now the wait for arrival.

You’ll love it just give the stones some time to break in.

 

[dalefuller]

Actually that might be the best place for it (rearward) so the curved tip stays at a similar bevel. BTW, I just scored a WE130 for myself - now the wait for arrival.

Congratulations. I've been using one for a couple of weeks now. I'm still right at the beginning of the learning curve, but the stones are starting to break in and it does make a difference. There are some good videos on the WE website in their blog. Suggestions for working with blades like the Military and PM 2, different ways to clamp the knife blades, etc.

Enjoy!

 

[Officer's Match]

Congratulations. I've been using one for a couple of weeks now. I'm still right at the beginning of the learning curve, but the stones are starting to break in and it does make a difference. There are some good videos on the WE website in their blog. Suggestions for working with blades like the Military and PM 2, different ways to clamp the knife blades, etc.

Enjoy!

Thanks Dale, I'll be sure to check those out prior to touching any decent blades.

The one I'm getting has the split & self centering vice jaws, purportedly to aid in holding those type of blades with a complete distal taper grind. I'll be anxious to see how that works. I've also got the "advanced alignment gauge" that has a grid pattern, so I'd imagine that can be helpful to setting the edge position to an optimal and repeatable spot. I'm thinking a quick picture of the blade + "AAG" (grid) would be a great way to record it.

Mine is coming with diamonds up to 1000, ceramics at 1200/1600 and at 1.4/0.6 micron and leather with 1.0/0.5 paste. I wonder if the diamond 1500/glass (for film) set is worth adding?

 

[dalefuller]

I got the ProPack 1 from Going Gear. I have stones up to 1200 grit and strops that I haven't used yet. I'm a functional sharpener. Once I get to the point I like on a blade for what I use it for, I stop. The UF Spyderco rods or the green strop block from Knives Plus is about as fine as I go.

I actually still do my touch-ups with the Spyderco rods or strop blocks. The WE is for more serious repair or resharpening jobs.

 

[LarryT]

I'm going to mess with ya all and say as you grind your edge away the angle is slightly changing still as the hone lowers itself. You know like grinding your roof away. The top point is fixed but the roof is getting ground down. Its negligible stuff, maybe noticed if you reprofile something thick. Your angle cube might show thicker angle afterwards. Consistency is what's important with guided system, so yeah probably doesn't matter, but it's a theory.

Was reading through this thread again and it sparked up a new question. I have to believe your “theory” is 100% correct. Just to make sure... so if the tip of a knife is at a lower plane than the straight portion, in theory it will have a a greater angle than the straight portion of a blade because it is at a lower plane than the straight portion correct?

 

[LarryT]

I would love to hear anyone’s input on this!!! Or a link to a thread that already explains this.

 

[brasileiro]

 

[LarryT]

I’ve watched that video and that’s not what I’m saying. I feel like that video only refers to a completely straight edge knife.

 

[jalapeno]

Was reading through this thread again and it sparked up a new question. I have to believe your “theory” is 100% correct. Just to make sure... so if the tip of a knife is at a lower plane than the straight portion, in theory it will have a a greater angle than the straight portion of a blade because it is at a lower plane than the straight portion correct?

Hi Larry, just to review what I think is contained in this thread, a straight edge will maintain a constant sharpening angle, even if the straight edge is tilted in the clamp. In other words, the straight edge does not (as I was thinking initially) have to be perpendicular to the centerline of the clamp.

But, most knives have at least a curved tip. This brings in a different geometry question, dealing with a constant radius circle. Let's say you have a chef's knife with an 8" blade clamped in a wicked edge, and let's say you have the knife clamped (left to right position) so that a point 3" in from the tip is in the center of the clamp.

Now lets say you have your desired angle set and the distance from the pivot joint on the sharpening rod to the point it rests on the clamped knife's edge is 7" (I just picked that number at random but probably close). This 7" radius is the "constant sharpening angle" radius (Anthony Yan's paper goes into a lot more detail on this).

So if you move the sharpening rod to the tip of the knife and it hits the exact same 7" point on the sharpening rod, it will sharpen the tip at the same angle as the middle of the blade, even though the tip is in a lower plane. This is only true along this circle of 7" radius.

But let's say hypothetically the sharpening rod hit the tip at 8" instead of 7. That would mean you'd want to shift the knife further to the left in the clamp (but keeping the straight part of the blade at about the same height) so that it would hit the tip at 7"

There's some "close enough" involved in this. But I couldn't tell you if the tip hit at 8" if it would produce a visually bad bevel unevenness. But I'd be willing to bet if it hit at 7-1/4 inches that would be close enough to give reasonably uniform bevel width across the whole blade.

The trouble is, there will be many knives where you can't get it perfect. Or maybe you get the very tip perfect but due to a strange curve shape that isn't very circular, the curved portion would have a slightly different bevel than the tip and the flatish portion of the blade. So you have to settle for getting it as close as you can for a given blade since there probably aren't many blade with a curve toward the tip that matches the radius of the wicked edge rod.

 

[LarryT]

Hi Larry, just to review what I think is contained in this thread, a straight edge will maintain a constant sharpening angle, even if the straight edge is tilted in the clamp. In other words, the straight edge does not (as I was thinking initially) have to be perpendicular to the centerline of the clamp.

But, most knives have at least a curved tip. This brings in a different geometry question, dealing with a constant radius circle. Let's say you have a chef's knife with an 8" blade clamped in a wicked edge, and let's say you have the knife clamped (left to right position) so that a point 3" in from the tip is in the center of the clamp.

Now lets say you have your desired angle set and the distance from the pivot joint on the sharpening rod to the point it rests on the clamped knife's edge is 7" (I just picked that number at random but probably close). This 7" radius is the "constant sharpening angle" radius (Anthony Yan's paper goes into a lot more detail on this).

So if you move the sharpening rod to the tip of the knife and it hits the exact same 7" point on the sharpening rod, it will sharpen the tip at the same angle as the middle of the blade, even though the tip is in a lower plane. This is only true along this circle of 7" radius.

But let's say hypothetically the sharpening rod hit the tip at 8" instead of 7. That would mean you'd want to shift the knife further to the left in the clamp (but keeping the straight part of the blade at about the same height) so that it would hit the tip at 7"

There's some "close enough" involved in this. But I couldn't tell you if the tip hit at 8" if it would produce a visually bad bevel unevenness. But I'd be willing to bet if it hit at 7-1/4 inches that would be close enough to give reasonably uniform bevel width across the whole blade.

The trouble is, there will be many knives where you can't get it perfect. Or maybe you get the very tip perfect but due to a strange curve shape that isn't very circular, the curved portion would have a slightly different bevel than the tip and the flatish portion of the blade. So you have to settle for getting it as close as you can for a given blade since there probably aren't many blade with a curve toward the tip that matches the radius of the wicked edge rod.[/QUOT

Hi Larry, just to review what I think is contained in this thread, a straight edge will maintain a constant sharpening angle, even if the straight edge is tilted in the clamp. In other words, the straight edge does not (as I was thinking initially) have to be perpendicular to the centerline of the clamp.

But, most knives have at least a curved tip. This brings in a different geometry question, dealing with a constant radius circle. Let's say you have a chef's knife with an 8" blade clamped in a wicked edge, and let's say you have the knife clamped (left to right position) so that a point 3" in from the tip is in the center of the clamp.

Now lets say you have your desired angle set and the distance from the pivot joint on the sharpening rod to the point it rests on the clamped knife's edge is 7" (I just picked that number at random but probably close). This 7" radius is the "constant sharpening angle" radius (Anthony Yan's paper goes into a lot more detail on this).

So if you move the sharpening rod to the tip of the knife and it hits the exact same 7" point on the sharpening rod, it will sharpen the tip at the same angle as the middle of the blade, even though the tip is in a lower plane. This is only true along this circle of 7" radius.

But let's say hypothetically the sharpening rod hit the tip at 8" instead of 7. That would mean you'd want to shift the knife further to the left in the clamp (but keeping the straight part of the blade at about the same height) so that it would hit the tip at 7"

There's some "close enough" involved in this. But I couldn't tell you if the tip hit at 8" if it would produce a visually bad bevel unevenness. But I'd be willing to bet if it hit at 7-1/4 inches that would be close enough to give reasonably uniform bevel width across the whole blade.

The trouble is, there will be many knives where you can't get it perfect. Or maybe you get the very tip perfect but due to a strange curve shape that isn't very circular, the curved portion would have a slightly different bevel than the tip and the flatish portion of the blade. So you have to settle for getting it as close as you can for a given blade since there probably aren't many blade with a curve toward the tip that matches the radius of the wicked edge rod.

Thank you for the response but I just don’t understand how a straight edge when tilted will maintain the same angle. It is on a completely different plane. I do partially understand what you mean about the radius though and how there’s going to be a "sweet spot" although it would still have some sort of slight variation unless you got it completely perfect.

 

[cbwx34]

Thank you for the response but I just don’t understand how a straight edge when tilted will maintain the same angle. It is on a completely different plane. I do partially understand what you mean about the radius though and how there’s going to be a "sweet spot" although it would still have some sort of slight variation unless you got it completely perfect.

Think of the pivot as a "point"... a point doesn't "see" parallel... it only sees a certain distance. Once that distance is set, it sharpens at the same angle. (It may be a different angle because the distance to the pivot changes... but once set, the angle along the straight part doesn't change). All you're actually making it parallel to is the clamp (or ground)... the pivot couldn't care less. Think of it this way... draw a small circle on a piece of paper... now draw a line parallel to that circle.

If you need a visual... clamp the blade at an angle, then rotate the entire W.E. so that the blade is now 'parallel' to the ground or table, and you might see it better.

BTW, while the angle in the curved portion does change, it's not really because it's changing height... it's because of what jalapeno is saying. This is why you can move a blade forward or backward in the clamp, and have a different outcome in the belly to tip area.

A lot of this seems counter-intuitive to what seems to be "right"... and still makes my head hurt when I think about it.

 

[Gritomatic]

The trouble is, there will be many knives where you can't get it perfect. Or maybe you get the very tip perfect but due to a strange curve shape that isn't very circular, the curved portion would have a slightly different bevel than the tip and the flatish portion of the blade. So you have to settle for getting it as close as you can for a given blade since there probably aren't many blade with a curve toward the tip that matches the radius of the wicked edge rod.

The curved shape does not have to be circular in order to have the constant angle. The straight edge and the radius curve are just 2 instances of equiangular shapes. There is the infinite number of equiangular shapes. If a cutting edge fragment corresponds to any, the constant angle will persist.

 

[Gritomatic]

BTW, while the angle in the curved portion does change, it's not really because it's changing height... it's because of what jalapeno is saying. This is why you can move a blade forward or backward in the clamp, and have a different outcome in the belly to tip area.

Awkward shapes could give the biggest contribution to angle change among all factors. For instance, small karambit. The sharpening angle can jump to 90 degrees in specific circumstances. The reason is substantial tilting of a sharpening stone when karambit is clamped.

 

[jalapeno]

Thank you for the response but I just don’t understand how a straight edge when tilted will maintain the same angle. It is on a completely different plane. I do partially understand what you mean about the radius though and how there’s going to be a "sweet spot" although it would still have some sort of slight variation unless you got it completely perfect.

Hi Larry, this is definitely a brain teaser. Different visual aids work better for different people, so maybe this one will help. I find it easier to visualize on a Wicked Edge type of system for whatever reason.

Think of the line of the blade’s edge that you’re grinding a bevel on as just "a line on a plane."
In the drawing I have a plane (in green). Maybe think of this as a piece of thin, inflexible plexiglass (or metal or whatever) but where you have it mounted to the pivot point of the sharpening rod (the red dot) so it’s co-planar with the sharpening rod.

Lay that plane across the blade edge (first with the blade edge horizontal). The blade is shown in orange.

The dotted red lines represent the different angles you could pivot the sharpening rod at, and these are all lines on the green plane. I also have a profile view of this setup.

The WE sharpening stones go on the rods, and the face of each sharpening stone lays flat on the plane no matter which side-to-side angle the rod is at (because the sharpening stones can rotate on the rods). As you scrub the sharpening stones up and down to abrade the edge, they stay in constant contact with the plane. Since the plane is fixed at the same angle everywhere, so too are the faces of the stones.


Now tilt the blade in the vise so it’s no longer horizontal:

Note that the line of contact between the plane and the blade edge is still just a line on the plane. But the spherical pivot joint allows the plane to still conform to the blade's edge no matter what the tile angle is. So, while the angle of the plane itself may change slightly between the 2 drawings, it is fixed at a constant angle in both individual cases.

If you set your sharpening angle to the same in both cases (using an angle cube, not the relative angle markings on the WE angle bar scale) with the sharpening stone at the centerline of the vise, the constant sharpening angle will also be the same in both cases.

Does this help?