Bark River edge angle and can I sharpen it on the Lansky guided system?

[EdgePal]

You have a Lansky, that is good. Now, bend the small part of the guide rod backwards about 8 degrees. This means that when you mount the guide rod to the sharpener the sharpener makes a angle downwards 8 degrees. Now your Lansky can sharpen convex edges.

The bended part of your guide rod is rather long. Use that length to mount the sharpener as long away from the long part of guide rod as possible to start with. Use the magic pen and grind - and se how the sharpener now convex your edge. Change then so that the sharpener is so close as possble to the guide rod - and grind again. It now makes a little different convex curve.

In this way can you use the different degrees and make a longer convex curve.

If you lock your Lansky in a vice in about 8 degrees, put the sharpener on the edge, and use a Angle Cube, you can meassure how big convex angle your Lansky makes. If it is to big convex sphere, make the bend onnthe guide rod from 8 to 6 degrees. The convex movement will then be less.

This is not a theory. I use this principle on all my sharpening tools thins more then 10 years - and it works perfect. The result is a perfect convex sphere.

Thomas

 

[calc]

The diagram made sense to me.

Thanks. I wasn't trying to put misinformation out there, just a helpful method of visualizing.

Any V bevel that has a primary and secondary grind can be made more streamlined by convexing it - smoothing the shoulders out.

Definitely. Of course a lot depends on how it was ground in the first place, but I've convexed a v edge before and it definitely had a more streamlined profile in the end. I have trouble thinking of what advantage a convex edge not ground more acutely offers.

You have a Lansky, that is good. Now, bend the small part of the guide rod backwards about 8 degrees. This means that when you mount the guide rod to the sharpener the sharpener makes a angle downwards 8 degrees. Now your Lansky can sharpen convex edges

This is a very, very interesting method. I've never thought of this before. Do you happen to have pictures of your results?

 

[Twindog]

The problem with the diagram -- and the reason that it is misleading -- is that you show the V edge being less acute on the conversion. You could also convert the convex edge to a more acute V edge.

It's like saying mammals are more vicious than fish, and to prove it you compare a lion to a goldfish. You could also compare a lamb to a shark and prove just the opposite.

 

[EdgePal]

https://m.youtube.com/watch?v=nynku3GQOoY

This is a video I did for some years ago. The video starts with showing a Angle Cube standing on the sharpener horder, you can read the degrees on the Angle Cube.

This small bend Fores the sharpener to make a controled curve across the edge, exactly the same controled curve every time = the edge will be convex with a perfect convex sphere.

I have not done this with a Lansky - but I know that it works on all sharpening rools that use guide rods. I have used a Gatco, it works perfect, just bend the guide rod about 8 degrees just behind the sharpener.

Other sharpening tools must use other solutions.

The video shows how I grind a convex edge with 3,3 degree convex sphere and with a cutting edge in 26 degree total edge (if I remember correctly).

The bend on the guide sor encrease the angle with about 2 degrees. If you use the 15 degree slot - you have about 17 degree angle in the starting point. If you use the complete sharpeners length, you will get about 3 degree convex sphere.

_______________\ this is how you must bend your guide rod, about 8 degree backwards - and then use it as you use

straight guide rod. You nearly do not feel the "convex movement" the sharpener makes - but it is there.

Thomas

 

[Rey HRH]

The problem with the diagram -- and the reason that it is misleading -- is that you show the V edge being less acute on the conversion. You could also convert the convex edge to a more acute V edge.

It's like saying mammals are more vicious than fish, and to prove it you compare a lion to a goldfish. You could also compare a lamb to a shark and prove just the opposite.

Can you prove the V edge is less acute on the conversion? Or is it an optical illusion for you? The Vs in both diagram appear to have the same angle to me.

You're trying to argue against something the poster never stated. I doubt he has a hidden agenda to subliminally advocate what you are saying he is projecting with the image.

At worst, he may have gotten his left and right switched but the substance of his words and the diagram point to how the two shapes relate to each other. And in each case, the variance appears to be made by removing the least amount of material.

 

[calc]

The problem with the diagram -- and the reason that it is misleading -- is that you show the V edge being less acute on the conversion. You could also convert the convex edge to a more acute V edge.

Sure. Hell, it's possible to convert the convex edge to a ridiculously acute edge at ~2 DPS, leaving us with a 4 degrees inclusive edge. Is that acute enough for you? If you're going to be pedantic, let's be pedantic - when you say acute, what's acute? You're criticizing me for not using exact measurements, but nether are you.

I didn't think I needed to spell this out because it's common sense.

It's like saying mammals are more vicious than fish, and to prove it you compare a lion to a goldfish. You could also compare a lamb to a shark and prove just the opposite.

Yeah... no. I'm not trying to prove anything. Again, let me be very clear, as I have several times already: it depends on how it was ground.

I hate to be a jerk, but you're putting words in my mouth. So I will explain it more clearly for you.

As I mentioned, when you grind in a v edge, you're grinding back into the blade profile. The reason the v edge on the right isn't as acute as the convex edge it was ground into is because I wanted to demonstrate that if you use the same edge angle as the v edge on the left, it's not going to be as optimal a cutter since the recession into the blade profile means it's going into thicker material and you need to adjust accordingly.

The reason I drew it this way is because I have convexed a v edge and then re-convexed it several times, and these are the issues I ran into. They should be obvious when diagrammed, but might not be readily apparent to someone first starting out.

 

[Twindog]

The OP wondered about the grind "angles" ( I would say "arcs") on Bark River's convex edge, and what would be the corresponding angle on his Lansky to convert it to a V edge.

The question cannot be answered unless we know something more about the Bark River edge than it's convex. How convex? What do you need the edge to do?

Any convex edge can be converted to a more acute V edge. Any convex edge can be converted to a more obtuse V edge. Which approach you choose depends on the starting point of the convex edge and how robust the V edge has to be to hold up to its intended use.

 

[HeavyHanded]

The OP wondered about the grind "angles" ( I would say "arcs") on Bark River's convex edge, and what would be the corresponding angle on his Lansky to convert it to a V edge.

The question cannot be answered unless we know something more about the Bark River edge than it's convex. How convex? What do you need the edge to do?

Barkies are ground pretty thin overall, ad by hand IIRC. The exact angle or shape of the arc are likely not standard but fall within a range. To do it on the Lansky without curving the guide rods would mean making the angle more obtuse, or converting it to a flat grind. A flat plane that includes the terminal cutting angle as it is currently set (whatever it is) will require heavy grinding way up the blade face.

 

[calc]

The question cannot be answered unless we know something more about the Bark River edge than it's convex

Good thing I didn't answer a question, then. I simply offered a method by which the OP can answer it for themselves.

 

[Twindog]

Barkies are ground pretty thin overall, ad by hand IIRC. The exact angle or shape of the arc are likely not standard but fall within a range. To do it on the Lansky without curving the guide rods would mean making the angle more obtuse, or converting it to a flat grind. A flat plane that includes the terminal cutting angle as it is currently set (whatever it is) will require heavy grinding way up the blade face.

The convex grind appears to change on differnent models, too. They advertise the Elmax Fox as having a thinner grind then usual because the steel is so tough.

It's difficult to give the OP advice without knowing something more about the profile of his convex edge. My guess is that it's not all that different from a V edge. And if he wants to convert the edge to a V edge so he can use his Lansky easily, he should just choose what would be an appropriate V angle for that steel and the kind of use he gives it.

The Woodland Special is a small knife with a 3.2 inch, full-flat-ground blade. The standard steel is A2 hardened to 58 Rc. The spine is fairly thick for a small blade: 0.145 inches. Depending on his use, he could probably choose a 15-20 dps edge on his Lansky. A2 is pretty tough, so maybe something closer to 15 dps would work best. If not, he could add a microbevel.

 

[Twindog]

Good thing I didn't answer a question, then. I simply offered a method by which the OP can answer it for themselves.

I didn't mean to bust your chops -- and your method can certainly work on some convex edge profiles. But we don't know what the OP's edge profile looks like. It could be a convex edge almost identical to a V edge, which most convex edges are. In any event, it doesn't really matter. Just choose the best V-edge angle for that small knife and go with that on the Lansky. He can adjust the angle up or down, depending on his actual experience.

 

[calc]

I didn't mean to bust your chops -- and your method can certainly work on some convex edge profiles.

It's fine, but I just want to be clear that I'm not advocating a method, just the possible pitfalls that might come with grinding a v edge into an otherwise convexed knife. The reason I am so adamant about being clear on this is that if this thread is found by someone in the future, they don't see what I drew and think that they can just start grinding away at their knife and ruin it. I want them to sit back, draw it out, and think before steel touches stone.

Just choose the best V-edge angle for that small knife and go with that on the Lansky. He can adjust the angle up or down, depending on his actual experience.

Yes, experience is the best teacher.

 

[EdgePal]

About convex edges, there is no machines that make convex edges. All knifes are produced with flat edges - and then, by hand, made convex on a beltgrinder. That means that all convex edges are unique. Knifes produced in a serial do not have exactly the same convex edge.

Bark River have a low convex edge with about 2-2,5 convex sphere. Fallkniven use a high convex sphere on around 6 degrees.

When I sharpen convex edges I mostly keep the convex sphere there is on the edge. If the user want me to change the convex sphere I do that.

Very often convex edges have not similar sides, and, the edge angle often changes along the edge. It is more or less normal that convex edges holds 20 DPS close to the handle - and 14 DPS close to the tip.

Thomas

 

[Twindog]

How do you measure the convex arcs on an edge? And how do you know if a convex arc is really a single arc or a blend of two or more arcs?

I can measure V edges with a laser protractor. It will also give a reading for convex edges, but I doubt that it's accurate. Arcs are not measured in degrees.

 

[EdgePal]

Twindog, i use my sharpening tool Chef when I meassure convex edges. I can adjust Chef to any convex edge.

I have not seen a convex edge that is a combination of two arces yet. I know they exists om some Japanese kitchen knifes - and I do not se any problems to sharpen also them, it is just a question of adjust my tool and grind the arces separatly.

Normal convex edges are made on a beltgrinder in a very simple way, they do not have multipel arces.

Thomas

 

[chiral.grolim]

... there is no machines that make convex edges. All knifes are produced with flat edges - and then, by hand, made convex on a beltgrinder. That means that all convex edges are unique.

1) Belt-grinder is a machine
2) All knives are produced with no edge at all, i.e. unsharpened, where-after they may be sharpened by a human being or by a machine holding them against a grinding wheel or plate or belt. Are opinel's convex? They're machine ground, and not with a high level of uniformity from blade to blade. Benchmades are each given a unique edge by a man at a wheel. Becoming convex does not entail unique hand-grinding, nor does a flat-grind negate it, nor does machine-grinding prevent it from being unique.

For the record, I resharpen my knives to ~15-dps. On my thin blades, the edge-bevel is too small to be able to differentiate a slight convex from flat. On thicker blades where the edge-bevel is more evident, I try to convex at a much shallower angle to thin the edge to where i want it and make for a smooth transition from the edge-bevel into the primary... but the edge itself is usually closer to flat.

Here's a simple image of 4 knives, 3 with the same edge-angle - can you tell which are convex vs flat? Which part matters?

EDIT to add: Here is a similar schematic of my old BRKT Bravo 1 overlapped 2 other knives - note how flat this BRKT:

 

[EdgePal]

Chillar.grolim,

1. A beltgrinder is a machine - with a human holding the knife. Humans have 17 joints in their arms, from the sholder out to the finger tips, that means that 34 joints are involved to hold the knife. 34 joints cant repeat a constant convex sphere. That is impossible. Study a industrial robot. How many joints can you se - and how exact are they? No insustrial robot has 34 joints...

Flat edges are made with machines where the knife is hold by the machine in a fixed position, all knifes in the same position. The "sharpener" is also "hold" by the machine, and the sharpener make the same movement every time. At least here. i do not know how knifes are produced in US. I do not belive that flat edges are made by hand, that would simply cost to much. And, of cause, i talking about knife producing companys

We can of cause discuss what is exact. It can differ a little in angles becouse of the sharpener wheel slowly worns out... Somewhere we must decide where the point is we say is exact. Is it 1/10 of 1 degree, 1/100 of 1 degree, 1/1000 of 1 degree or a miljon of 1 degree? Or less?

2. Shall we diacuss things that, I think, all people allready knows?

For the record: no, I cant tell that from a drawing. I can tell that from real knifes. I have never sharpen a drawing.

Convex edges is a big subject, they can be very thin and very thick and the convex sphere can be very small and very big. Convex edges are just one type of edge along other types of edges, good for some things, bad for other things. Depending on what you are doing with your knife, you choose the type of edge that work best for just you.

My outdoor knifes have convex edges, they work fine for me. My wood working knifes have flat edges in different degrees depending on what type of wood I work in. Flat edges are superial for some type of work, convex are superial for other type of work.

Convex edges are not better or more durable then other type of edges, in my opinion.

I have find a method to sharpen any convex edge - and then maintain them in exact the same convex sphere. If you use that method you take away very little material from the blade. In my mind, that is a very nice thing. I do not keep that knowledge as a secret, I inform other about it so that they can use it - if they are interested.

If you are interested of convex edges, try it. i think you will love it becouse it gives you control of the convex sphere.

Thomas

 

[arnisb]

EdgePal
What tool do you use for convex sharpening ?
Please provide some pictures ...

 

[EdgePal]

Arnisb, i use my tool EdgePal Chef. You can visit my homepage: www.edgepal.com and go to the English side.

On the Swedish side are more videos about Chef, (in Swedish) but there is also a short text in English that describe what the video shows.

It is my hobby to invent, construct and produce sharpening tools - and I make my tools by hand.

Thomas

.

 

[chiral.grolim]

1. A beltgrinder is a machine - with a human holding the knife...

Flat edges are made with machines where the knife is hold by the machine in a fixed position, all knifes in the same position. The "sharpener" is also "hold" by the machine, and the sharpener make the same movement every time. At least here. i do not know how knifes are produced in US. I do not belive that flat edges are made by hand, that would simply cost to much. And, of cause, i talking about knife producing companys

A belt-grinder produces a natural convex curvature without the need of joints, just as a grinding-wheel produces a concave curvature. There is no need for a human to hold the knife, a machine can do it just as easily. you only need the joints to produce a convex edge off of a non-flexible surface like a benchstone.

Opinel knives are machine-made, machine-ground with a convex blade (magnet-arm holds each blade against abrasive belt which flexes as it grinds the steel) - skip to 1:38:
[video=youtube_share;KNELKUpH10k]http://youtu.be/KNELKUpH10k?t=1m38s[/video]

I mentioned Benchmade (a major US production company) flat-grinding knives "by hand" i.e. human holding blade against grinder - skip to 1:00:
[video=youtube_share;tTbHk3IzFcw]http://youtu.be/tTbHk3IzFcw?t=1m[/video]

For the record: no, I cant tell that from a drawing. I can tell that from real knifes. I have never sharpen a drawing.

Convex edges is a big subject, they can be very thin and very thick and the convex sphere can be very small and very big. Convex edges are just one type of edge along other types of edges, good for some things, bad for other things. Depending on what you are doing with your knife, you choose the type of edge that work best for just you.

The radius of curvature or "arc" can be very slight or very dramatic, noticeable or not, depending on the angle of incidence and radius of the arc. A convex edge is not "bad" for anything, any type of use. I strop every every blade I can on a soft backing to produce a convex edge, be it for shaving or chopping or draw-cutting. By creating this curvature in the bevel, I take off less support material and so provide the blade more strength, but I also round-down the bevel-transition areas to reduce stress-risers (essentially creating a "back-bevel"). That is all that convex is for, those 2 things - ease of transition, stouter blade or edge. In the top schematic, red-blade has a slight convex in the primary bevel but dramatic rounding of the edge-shoulders down to the apex. The green and blue have flat primary bevels but similarly rounded shoulders, less noticeable because the primary-grind is so much thinner. If i grind a flat edge and then strop to the apex, i increase the apex-angle via the curvature produced. I can also round-down the bevel-shoulders while leaving the apex-angle intact.

In summary, there is nothing that a convex edge is not good for, and convex edges can indeed be produced by machine, but most sharpening-tools are more easily used to produce a flat edge and most companies do that, that is all.