Wire Edge and Chipping on the same blade, is this hard to explain?

Maybe the edge steel is stressed, you can simply lightly cut into your sharpening stone a couple times to remove the weak metal, then re-apex it, being careful of burr formation. The reapexing takes no time, you are removing enough steel from the edge it will be like you cut up a box, barely anything
 
I'm certainly no expert, but it seems to me that you are overlooking the obvious- your angle is too acute for the use you are subjecting it to. Dial back your angle to about 20* and see what happens. My hunting knife that I have hand sharpened and used hard for decades has never chipped. I got a Wicked Edge for Christmas and decided to take the angle down to 17* to see how sharp I could get it. Mistake! The first time I split a pelvic bone with it, I put a large nick in the edge. I reprofiled it to 22* and all is well again.

My conclusion: there are two kinds of sharp - braggin' sharp and workin' sharp. If your blade stays in your pocket except to push cut a piece of paper to amaze your friends, then braggin' sharp is fine. Working knives need a working edge appropriate for the task.
 
Pursuit Hunter said:
I'm certainly no expert, but it seems to me that you are overlooking the obvious- your angle is too acute for the use you are subjecting it to. Dial back your angle to about 20* and see what happens. My hunting knife that I have hand sharpened and used hard for decades has never chipped. I got a Wicked Edge for Christmas and decided to take the angle down to 17* to see how sharp I could get it. Mistake! The first time I split a pelvic bone with it, I put a large nick in the edge. I reprofiled it to 22* and all is well again.

My conclusion: there are two kinds of sharp - braggin' sharp and workin' sharp. If your blade stays in your pocket except to push cut a piece of paper to amaze your friends, then braggin' sharp is fine. Working knives need a working edge appropriate for the task.
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15 per side should hold up with NO problems on almost any steel. If De-stressing the edge doesnt fix it, I blame HT. Most my knives are used at 15, with the exception of one that was used at 13dps, another used at 10dps, and one at 17dps that I cant be bothered reprofiling the back bevel on for a 15 dps edge. I say destress the edge before trying again, otherwise microbevel it at 17-18 degrees ( which is strong for anything unless youre cutting through large bones)
 
knifenut1013 said:
Like the diagram shows, you can't add metal.

So because when you sharpen convex you make the apex more obtuse due to held angle suddenly everyone sharpens convex in this way? If you change the angle you change many factors, if you simply sharpen convex while maintaining the same apex angle you only change the shape.

You are trying to factor in angle when we are only speaking of shape.
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Incorrect on both counts, which is odd as you quoted the exact description. Diagram (B) presents convex sharpening while holding the same angle. During sharpening, apex angle is maintained in spine-to-hone height. For flat-bevel grinding, a solid flat hone is used. The result of grinding down the pink-bevels with a flat hone is the gray bevels. For convex-bevel grinding, a curved or semi-flexible hone is used at the same angle, same spine-to-hone height, and the bevel has the same height & shoulder width as before, but since the hone curves around the bevel it alters the shape (as you say) and presents a more obtuse apex than the grind angle would present on a flat hone. Again, you hold the same angle but get a different result (violet vs. gray).

Only in diagram (C) do you hold a different angle, evident from the altered bevel height (again, violet & gray vs. pink). But again, the convex-grind is more obtuse than the flat grind and "puts more metal behind the edge" despite grinding at the same angle and producing a bevel of the same dimensions. NO ONE can make a flat bevel more obtuse than a convex bevel held at the same angle, it is geometrically impossible. And a convex bevel can only be made more acute than a flat bevel by altering the held angle and so changing the bevel dimensions, often significantly.

As I wrote before, if you want a more robust edge, EITHER reduce the bevel height (different held angle) OR sharpen convex and maintain the same bevel height (i.e. same held angle). Sharpening convex changes the shape AND apex angle without changing the held angle, which is, again, exactly the point.
 
Chiral & Knifenut1013 - IMHO both of you are correct, merely disagree on semantic/interpretation. Me too, I had discussed & mis-understood by others on this convex concept. For me, most of the time, convex means 'Practical convex'.

convex.png


For 'Extreme', we are looking at nearly double or half the bevel angle. Even in the cases of micro-bevel - e.g. inclusive * 15/25 (67%); 20/30(50%); 30/40(33%) - we're far from doubling the angle. Stropped edges are mostly convex micro-bevel anyway :D

Chiral - :thumbup: nice illustrations.
 
knifenut1013 said:
Does no one understand that you cannot draw the convex outside of the V edge? You cannot add metal.

Take a look at this thread for proper representation of edge drawings comparing V and convex. http://www.bladeforums.com/forums/s...tages-of-a-convex-edge?highlight=convex+edges
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I don't think they do. This exact subject was went through with fourty-two blades a couple monthe ago. I am with you knifenut, it seems pretty straight forward. When you sharpen you remove material no matter how lightly or how fine the abrasive is you use.
 
Lol - it's semantic again. All it's matter is the end-result shape, don't matter whether it started as a square/hexagonal shape. Convex is just a curve with 2 or more control points with some radius/pt (degree of curvature). Each point could be symmetrical or cusp. Apex is a cusp point connecting to the curve or line(chisel) on other side.
 
Thanks Chris, I thought it was simple.

Bluntcut,

No, this is simple. This is about convex vs a V edge and the claim that convex is more durable.

Changing shape does not add durability it only reduces drag.

To increase durability you need to change the apex angle to a more obtuse one. This however has nothing to do with convex sharpening which is a changing of shape.

If you adjust the angle to a steeper one and change the shape by convex sharpening then you will gain durability and decreased surface friction.
 
This isn't a question of semantics, it is question of geometry and the definition of words.

For example, convex = curved or rounded outward; (math) a continuous function with the property that a line joining any two points on its graph lies on or above the graph; from Latin convexus = carried out/away from.

"Convex" is defined as away from flat, an alteration of shape that can ONLY be accomplished by an increase in angle, i.e. more obtuse, to a form which lies outside or above the corresponding flat plain. knifenut1013 is comparing non-corresponding shapes/functions/figures. His base premise is false.

Now, a key point of his problem seems to be what angle is being measured (or not measured, really) and what shapes are being compared.

convex%25202.jpg


In practice (sharpening, and other practices as well, like aerodynamics), the angle being measured is the "held angle" or "angle of incidence" between hone surface (flat gray) and spine-center (red line). NOTE: If this is NOT the angle you are using to grind your bevel, then you are very likely not using ANY angle measurement at all but instead merely extrapolating after-the-fact. For example, the violet-line in the diagram is presumed tangential to the precise apex-angle of the green convex... but the precise apex-angle of the green convex cannot be measured without precision instruments or precise knowledge of the geometry of the curve(s) at the point of bevel intersection (the true apical angle of incidence of a curved shape). However, such measurements are unnecessary for the purpose of this discussion as the measured apex and tangent bevel do not produce a triangle of similar geometry beyond an infinitesimally short shoulder height (i.e. at the point of bevel intersection).


Draw a chord perpendicular to the hone surface that meets the spine-center line to form a triangle. This triangle is geometrically "similar" to the smaller triangle formed by drawing a chord perpendicular to spine-center that intersects the bevel shoulder (light blue triangle). These triangles are similar because their dimensions are directly proportional, their angles equal - these triangles even share an apex!

Altering the shape of the triangle by increasing or decreasing the height of the bevel along the spine-center WITHOUT a proportional change in shoulder thickness (which necessarily changes the angle of incidence) produces NON-similar triangles. (For some reason, knifenut1013 insists on comparing non-similar geometric shapes and thereby reaches a conclusion that contradicts geometric and mathematical definitions.

However, one can alter the shape of the triangles without changing the angle of incidence, shoulder width, or bevel height by using a curved or flexible hone instead of a solid hone. How much the shape is altered is controlled by the amount of deformation and curvature (again, away from flat) of the hone. The result is a thicker bevel, one with more metal that it would have if ground flat at the same angle of incidence.

To make a convex bevel thinner than a flat bevel, one MUST change the angle of incidence, but the result is still thicker than the flat bevel ground at that new angle and it is the flat bevel at that angle which informs the use of the term "convex" to describe the rounded out bevel - again, "out". "Out" from what?

This is not about the elementary statement, "you can't add material, only remove it." Of course you cannot add material. This is about drawing the correct correlations when using the term "convex". "Convex" is defined by "out from the correlated flat". "Out" cannot be "in" at the same time in the same context.
 
You can keep tying to point out how I am wrong with long posts and poor drawings but this is about the original comment that convex is more durable.

Only a change in angle will affect the outcome of edge apex performance, convex is still a term describing a shape.

And if that's still confusing here's the real definition http://i.word.com/idictionary/convex
 
knifenut1013 said:
Angle of the apex still rules.

Convex does NOT translate to stouter, stronger, or tougher. It's actually thinner.
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knifenut1013 said:
You can keep tying to point out how I am wrong with long posts and poor drawings but this is about the original comment that convex is more durable.

Only a change in angle will affect the outcome of edge apex performance, convex is still a term describing a shape.

And if that's still confusing here's the real definition http://i.word.com/idictionary/convex
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1) Your link is iPhone exclusive. But anyone can investigate if I quoted a correct definition. I did.

2) This is about FOUR things:
a) your comment above that convex is thinner than flat, as it clearly is NOT when understood in context of the definition
b) describing a shape means describing angles correlated with that shape, so the two are really inseparable
c) One can change the shape and true apex angle via convex sharpening WITHOUT changing the sharpening ('held') angle, the bevel height, or the shoulder thickness which are the measured attributes in everyday sharpening.
d) Angle of the apex does NOT solely determine edge apex performance, indeed bevel thickness & height and level of edge refinement (polish) have a MUCH more significant effect both on edge durability and cutting performance. If you doubt this, check the physics. OR ask Jankerson about his edge retention tests in which every knife is sharpened 15-dps. THIS post may be enlightening. To further illustrate this, look again at the edge-flex videos posted and ask yourself how much an altered apex angle would affect the outcome without respect to edge thickness. I hope this helps.

3) I'm using MS-Paint for the pics - crude but effective ;)
 
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