Convex edge thoughts ?? I'm not a fan

V

Vegas Blade

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Feb 9, 2012
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As the title states, I was in the garage today playing with some toys (boys will be boys) and I did a little test. My Bark River Bushcrafter in 3V vs. my Hinderer in S35VN. They are both out of the box edges. My Hinderer will cut CIRCLES around the Barkie. The Hindi will push cut newspaper and shave hair, the Barkie....not so much. Now I KNOW 3V is bad arse steel, and the Barkie is a great bush knife, it's just that the convex edge is NOT as sharp. Thinking about re profiling it to a more traditional V grind. Give me some of your thoughts.
 
Seems you're focusing on one aspect of the edge and not the knife as a whole. It could be that your Hinderer has a thinner edge. Could be that the belly/blade shape of the Hinderer is better for what you're cutting. Could be that the ergos of the Hinderer presents the edge in a matter that makes it more efficient for cutting what you're cutting. There's a test here that's pretty popular about the different steels but it only gives you anecdotal evidence of what's going on IMO because different knives of different geometries will perform differently even if the steel, hardness and even the same edge angle are all the same. My guess is if you give it a V grind it will still not perform as well as your Hinderer but give it a shot. Don't know til you try.

My best performing knives have been convexed but again I attribute that performance to other aspects of those particular knives in addition to the convexing. YMMV
 
Not a stupid question at all. In fact, it's very logical. I tried, I touched it up on a diamond stone, going backwards, then I leather stropped it. It was "better", but I think the convex edge is just too thick. I know the convex edge is supposed to be stronger and all, but it's a 4" knife, not an axe. The convex may be better for bigger choppers or cleavers, but not smaller knives.
 
To have the best comparison of the two different edges it would be best to have blade grind, geometry and edge angle all very close to the same. .010 thickness behind the edge can make a pretty large difference in how a knife cuts. For example I think the difference would be pretty noticeable between a knife with an edge .010" behind the edge, and a knife .20" behind the edge. Given that the overall geometry of the two knives is similar.
 
You're trying to compare two different animals.

My convexed laminated VG10 Fallkniven F1 will push cut newspaper and split a hair, not just shave it. My ZT0550 ( sorry the closest I have to a real Hinderer) in S35VN will do the same.

Unless you are willing to buy another Hinderer, and convex it, your comparision isn't really valid.
 
Convex edges of equal edge angle as a V edge will actually be thinner. This is a case of edge refinement and sectional blade geometry. If the geometry of the Bark River was thinner than that of the Hinderer and the edge was equally refined then it would cut better. It's not a matter of convex edges not being good. It's a case of the convex edge and sectional geometry of your Bark River not being as good for the particular task as that of your Hinderer.
 
A convex edge can be just about anything you want it to be -- short, stout, obtuse or long, thin and acute. Who knows what you have. The V edge is usually defined by the edge angle (30 degrees or 40 degrees inclusive, etc.) With guided systems, you can get the exact angle you want.

Convex edges are more of an art form. It's freehand. Who knows what angle you get. Who knows if you have a good apex.

Personally, I can get a V edge much sharper than a convex edge, but that's because of my own limitations. I purchased a Gillson knife in CPM M4 at 64 HRc, and the convex edge is a thing of beauty. I chopped with it hard into a piece of clean, straight-grained Doug fir with absolutely no affect on the edge that I could determine. And it's as sharp as I normally get my V edges. The same test on a custom bowie in W2, also with a dull convex edge from the maker, showed serious damage with every chop. The same test with a bowie in 3V with a keen, 30-degree inclusive edge had dulled the edge.

All things being equal (edge height, width of the edge shoulder), the V edge will be more acute and cut better. But a convex edge can be made thin, as 42blades has mentioned , and cut extremely well.

The convex, however, requires much more skill to produce than a V edge in a guided system.

There are so many uncontrolled variables in the OP's observations that little can be learned.
 
Vegas Blade said:
As the title states, I was in the garage today playing with some toys (boys will be boys) and I did a little test. My Bark River Bushcrafter in 3V vs. my Hinderer in S35VN. They are both out of the box edges. My Hinderer will cut CIRCLES around the Barkie. The Hindi will push cut newspaper and shave hair, the Barkie....not so much. Now I KNOW 3V is bad arse steel, and the Barkie is a great bush knife, it's just that the convex edge is NOT as sharp. Thinking about re profiling it to a more traditional V grind. Give me some of your thoughts.
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Is push cutting newspaper and shaving hair what you want/need the knives to do? Or are you going to use them for something, uh, more relevant for testing their edges. Take the two knives out and use them on some wood--you'll get a different impression of the way they cut.

Different grinds/edges are designed for different things--you won't find any convex scalpels or paper cutters, but for a bushcraft knife or cutting flesh it works pretty darn well. You'd actually have to use the knives though to figure that out.

DJK
 
Twindog said:
All things being equal (edge height, width of the edge shoulder), the V edge will be more acute and cut better. But a convex edge can be made thin, as 42blades has mentioned , and cut extremely well.
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I would argue that "edge height" and "width of edge shoulder" are cosmetic rather than functional parameters and that it makes more sense to make judgments based on keeping angles constant.

Also, once initial convexing is performed there's not a whole lot of advantage in religiously maintaining a "perfect" convex. Just sharpen it as usual. It's not going to really going to make a significant difference. :)
 
The edge is defined by three points: the apex and the two shoulders. When all three of those points are in the exact same place, the V edge will have the more acute edge because, by definition, the convex edge sweeps outside the V edge lines before coming to the apex.

If you raise the shoulders on the convex edge, you can make the angle more acute and it's lines will sweep inside a V edge with shorter edge height.

A V edge is precise with a guided system and less precise freehanded. But the convex edge is only loosely defined. The convex edge is a work of art. It's freehanded and the angle can be anything. With any given two people, a V edge done on a guided system will be almost exactly the same.

On a convex edge, any two people will likely come up with quite different edge profiles. Both will say they have a convex edge, but their edges can be very different.

A convex edge should be defined by the three points that define the V edge. But in addition, it should be defined by the arc. I can draw a diagram, but it probably isn't needed. The convex edge starts at the shoulder and ends at the apex. If it's a tight arc that connects those two points -- an arc of a small circle -- the convex edge can be very fat. If it's a gentle arc -- say part of a circle the size of the earth -- you would not be able to tell if from a V edge.

So what is a convex edge? No one ever defines it. They don't define the three points that define an edge, they don't define the arc that makes it a convex edge, they don't specify the angle of the edge. It's just a loose term that we all pretend has some precise meaning. It should, but it doesn't.
 
Personally, I do not like convex edges. I did my own testing with a custom drop point hunter. It was convexed for me by someone else and I kept it that way for almost a year. It cut ok, but was a pain for me to sharpen. I recently reprofiled it into a V edge trying to keep the same dmensions of shoulder and apex. It is very sharp and much easier for me to sharpen with my equipment. Touching up on a strop or with some sandpaper is quick and easy. I also use the bottom of my coffee cup when out and about if needed. So, testing with the same knife for extended periods using it how I normally do has poven to me that this knife works best fo me with a V edge.


-X
 
Thinking about re profiling it to a more traditional V grind. Give me some of your thoughts.
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That Bushcrafter has a scandi-convex grind which should perform well for what it was designed for. I would consider why you purchased this bushcraft knife and what your intended use is before thinning or altering the edge. Perhaps a different knife would better suit your needs or it may just have a poorly finished original factory edge and correcting that might greatly improve your opinion of it.
 
Here’s a blade that shows a V edge and three different convex edges. The V edge is defined by three points: the apex and the two points of the edge shoulder.

The red line represents a convex edge using the same three points, with a tight arc. This convex edge is fat, stout and obtuse. It will be very strong, but not a good cutter, compared to the V edge.

The pencil line represents a convex edge using the same three points, but with a gentle arc. It’s still not as aggressive a cutter as the V edge, but it’s better than the red convex edge.

The green arc represents a convex edge where the shoulder was raised. This edge is almost as acute as the V edge, but also can cut deeper before the width of the blade begins to limit cutting ability.

Three convex edges, all very different. We always talk about convex edges as if they are all the same. They are not.

So, Fastriot got a convex edge profiled by someone else to standards he knew nothing about. Then he tried to resharpen it, but his own standard was most likely quite different than that used by the previous sharpener. If the original convex was like the red angle and he tried to resharpen it using the green angle, he would have to sharpen a very, very long time before he’d even approach the apex.

Convex angles can be awesome, but they can also be terrible cutters. Or anything in between. And because we talk about them without defining them, we usually end up talking past each other.

 
lord grimlock said:
i know i am fixin' to get crucified, but i hate convex edges. just a bigger pain in the ass to sharpen.:D
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Not by me. I dislike them as well. I find standard edges to perform perfectly fine. And It took a long time for me to learn basic sharpening. I dont feel like another learning curve for the very few times I could benefit from a convex edge.
 
Twindog said:
The edge is defined by three points: the apex and the two shoulders. When all three of those points are in the exact same place, the V edge will have the more acute edge because, by definition, the convex edge sweeps outside the V edge lines before coming to the apex.

If you raise the shoulders on the convex edge, you can make the angle more acute and it's lines will sweep inside a V edge with shorter edge height.

A V edge is precise with a guided system and less precise freehanded. But the convex edge is only loosely defined. The convex edge is a work of art. It's freehanded and the angle can be anything. With any given two people, a V edge done on a guided system will be almost exactly the same.

On a convex edge, any two people will likely come up with quite different edge profiles. Both will say they have a convex edge, but their edges can be very different.

A convex edge should be defined by the three points that define the V edge. But in addition, it should be defined by the arc. I can draw a diagram, but it probably isn't needed. The convex edge starts at the shoulder and ends at the apex. If it's a tight arc that connects those two points -- an arc of a small circle -- the convex edge can be very fat. If it's a gentle arc -- say part of a circle the size of the earth -- you would not be able to tell if from a V edge.

So what is a convex edge? No one ever defines it. They don't define the three points that define an edge, they don't define the arc that makes it a convex edge, they don't specify the angle of the edge. It's just a loose term that we all pretend has some precise meaning. It should, but it doesn't.
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Excellent points. Very informative.
 
The Bushcrafter isn't a "convex" in the traditional sense, it's a Scandi convex.

Also, these two knives have differing amounts of material behind their edge which makes the comparison inaccurate.

Lastly, you have to define what a convex is, just saying, "this knife is convex'd" is meaningless. Convex'd edges vary greatly from knife to knife and between the people sharpening them. I've had two identical knives from the same maker and it was obvious a different person ground one from the other. One was thicker and had a more obtuse edge while the other was thinner with less material behind the cutting edge. Again, same exact knife, same maker.
 
The issue that you're having with your Bark River is actually a pretty common complaint (at least I hear it a lot). It sounds like it has a fairly steep micro bevel from the factory. Once you reprofile it a bit to get rid of the micro bevel and create a smaller edge angle, it will cut much better.
 
@ Expwmbat, Sir, I assure you I use my knives. I cowboy, brand cattle, fix fence, cut hay bales, even been known to cut a little barbed wire. Don't misunderstand that just because that's what I was doing, that it is all I do. When you are working horseback, the best tool is the tool you have. It is impossible to have everything you "may"need. When you figure fencing tools, a length of wire, maybe a small chopper to clear vines and branches, a bottle or two of medicine, bunch of syringes or a vaccine gun, you get the idea. That said, if a knife isn't as sharp as it can or should be, it doesn't matter if I'm cutting bailing twine, leather, or shaving hair, it's a tougher than need be job. I said in my earlier post that I believe my Barkie may just be too thick of a convex. A thinner convex may be the cats meow. That's not what mine is though. Based on a couple of posts here, I'm not alone in my dislike for a convex grind.
 
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