Convex or V edge ?

avoidspam said:
This argument looks familiar!

We all find what works best for us and learn a little bit along the way.... I love Spyderco's and still carry one for EDC from time to time but the thinnest one I have (Delica 4) can't compete with my thicker bladed convexed knives (Svord/Bark River) when it comes to cutting deeply into green wood. The winner in my collection is the Opinel but I guess that would be cheating as it has thinner blade stock to start with.

Part of the fun of it all is we all cut slightly different things with slightly different knives, steels, edge geometry, cutting angle etc... And we all share our experiences here...., highly scientific:)
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Your perception is off here, or the perceived performance. ;)

Thinner blades just flat out cut better....

Lower edge angles just flat out cut better.


Take a knife that is ground very thin behind the edge say .005" and in say 1095 at 65+ HRC and it will perform so well it would be mind blowing to most people and it won't matter what the edge type is. ;)

Oh and it will peform (Cut better) better than any production blade and it will do it dull. ;)

It's called matching the knife with the steel at PROPER hardness with a PROPER HT for the task at hand, if all 3 line up we get what is called optimal performance.

Any one of those 3 aren't correct then adjustments have to be made to compensate.

But then we can only get that kind of harmony in CUSTOMS so people will have to make adjustments to compensate. :)
 
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I love the Opinel because it has a thin blade, coupled with full convex grind. There lies the clever bit in my mind because with those features they have been able to create a stronger blade than if it was a 'v' grind with a 'v' bevel on the same blade stock thickness (correct me if I'm wrong here, always happy to learn new stuff). Incidentally, I put a slight convex edge bevel on my opinel's to offer a little protection to the edge as I work the knife quite hard in green wood (within what I think are its capabilities).

I agree with Ankerson re: thinner blade and lower edge angles. My Bark River has a lower edge angle than my Delica, yet, if I lower the edge angle on my Delica to try and compete it starts to chip. Bear in mind I'm talking about purely deep cutting into green wood. Then, I can happily cut at 90% into a thumb sized piece of green wood, the bark River will happily keep cutting deeper purely with the pressure of my thumb. No such luck with the delica.....

More, more!:)
 
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avoidspam said:
I love the Opinel because it has a thin blade, coupled with full convex grind. There lies the clever bit in my mind because with those features they have been able to create a stronger blade than if it was a 'v' grind with a 'v' bevel on the same blade stock thickness (correct me if I'm wrong here, always happy to learn new stuff). Incidentally, I put a slight convex edge bevel on my opinel's to offer a little protection to the edge as I work the knife quite hard in green wood (within what I think are its capabilities).

I agree with Ankerton re: thinner blade and lower edge angles. My Bark River has a lower edge angle than my Delica, yet, if I lower the edge angle on my Delica to try and compete it starts to chip. Bear in mind I'm talking about purely deep cutting into green wood. Then, I can happily cut at 90% into a thumb sized piece of green wood, the bark River will happily keep cutting deeper purely with the pressure of my thumb. No such luck with the delica.....

More, more!:)
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The Opinel is a production knife so adjustments (Compromises) had to be made to strengthen the blade taking into count the variables of production knives and production heat treating ect.

It's not that those things they changed or did are really better, what that really means is those changes made that knife work within the variables of what production knives are.

That's were perception comes into play, we can't base them off of production knives because they are a compromise in the end, built for the masses.

Yes I know MOST people have production knives, that's a given and that is also why some myths and urban legends tend to get spread around.

There is perceived performance and then there is optimal performance, there is a huge difference between the two.
 
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I agree with Marcinek here ... "It's kind of pointless to have a knife discussion forum if you aren't going to niggle over detail about knives, isn't it?"

To everyone ... thanks for the civil discussion.

I definitely have a lot to learn on several subjects and knives are obviously a passion for all of us.

I still believe based on my own experiences that the shoulder is BAD, VERY BAD ...... kidding of course! lol :D

Several experienced and intelligent members have provided some very useful material for all and future members.

Brian
 
Wise, kind and funny words Brian:)

I guess I fit into the 'most people', from 'the masses' club. If I'm heading out to greet a typical Welsh day (wet/windy and cold) and I know I'm going to be working up to my ankles in mud, cutting everything from hessian, cement bags, DPC etc, I'll reach for the Opinel. Why? Because it costs £8 and the performance I get for that kind of money puts a smile on my face. If it breaks, I'l buy another.

I even wear a blue polo shirt as part of my uniform;)
 
Ankerson said:
You are talking about edge thickness here or thickness behind the edge and edge ANGLES.

Given the SAME thickness behind the edge and the SAME edge angle there would be no difference in cutting performance.

If the steel isn't holding or strong enough, that has more to do with the steel, HRC and the HT than it does with the edge type. ;)

So what is happening here is one is adjusting the edge type to the steel due to issues with the HT and low HRC, that has nothing to do with actual performance
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Yes, I'm talking about angles, comparing v-edge, scandi and convex at the same angle.

No, there is a difference given the same thickness behind the edge and the same edge angle (same blade). I'll give you an example. I live in Sweden and have an abundance of Moras and whatnot at my disposal, so I've done a lot of comparing and testing. I've convexed a LOT of factory-made scandis because they ALWAYS roll if you carve with them. They come with too keen of an edge. So, I either back the angle ever so slightly or I convex them. No edge roll. Same cutting performance (in practical terms). If we're talking theoretically then they would actually be less sharp as I've made the edge more blunt, so what you're saying about heat treats and whatnot applies to my statement, as it goes without saying. I adjust the edge to convex because it works well. All of my Moras, Hultafors etc. are now even more extreme at zero-ground convex and they don't roll, whereas they all did before with the scandi-grind. Yes, they are thinner and therefor cut better, but I've also slightly convexed the bevel on scandis, as most knifemakers do here (handsharpened) and then they don't roll either and in all practical terms my slightly convexed bevels and the original ones are the same dimensions. Convex works for bushcraft because it makes the edge stronger (less acute, shorter point), yet surgical sharpness is traded in for the cutting ability of a scandi after 2 minutes of carving. I would never convex my straight razors because I understand the advantage of the v-edge as it is always sharper (more acute at same angle), but that sharpness at it's most extreme (no edge roll on given HT, steel, whatever) won't last in bushcraft with a v-edge as well as convex does at no edge roll on same steel etc.

I'd love to know how many of the people that have posted in this thread actually do bushcraft with all the edge types discussed, because that's what I'm all about and I've used more knives in the field than I can remember. I leave my cardboard cutters v-edge or scandi and make my bushcraft blades convex for several reasons. Bushcraft isn't about pen on paper theory, where v-edge wins in sharpness, it's about what works and convex really does. Why the hell would Katanas have convex grinds on swords made to fight armor and saber grinds when meant to cut flesh exclusively? Compare that with knives where wood is a tough tester. It's old knowhow and there's nothing complicated about it. It just so happens that the convex edge or zero-grind works on knives exceptionally well, but it's not as cheap to produce so the knife world has become dominated by v-type-edges, so most people haven't handled convex knives enough to fully understand what they excel at. They're not just for axes.
 
Well a katana wasn't really used for cutting, but more similar to a chop. I've never had a v edge roll doing bushcrafting type stuff or using it on man-made things that are even harder on an edge. It's not really related to knives that are coming to you with a soft and/or thin edge. You can make several tent stakes with a Victorinox right out of the box and not roll the edge.
 
Bubba,

sure a Katana is for cutting (it's major use), as one does not chop with a Katana, but that's beside the point.

Of course you can carve with a Victorinox without it rolling. What I'm talking about is in response to Ankerson's reply about heat treats and steel and what extreme one can take an edge to (how thin) before it starts to roll.
 
I'm sure some people have used them to cut but if you watch someone practicing traditional techniques with a katana there is nothing really about cutting going on. It's the same type of techniques used for a jo or 4' staff except you stay on the handle and it actually penetrates. You always step into it and try to go deeply into or through the object, it's not like shaving wood or cutting a steak at all.
 
OK, this is off topic but I'll play.

No, one cuts with a Katana. It appears to be a chop, but one actually performs a cutting action at the same time. It increases damage. I didn't wanna go into a discussion about Katanas, I just wanted to give an example of how the two different grinds were used in the 1600s and whatnot.
 
I think it is just different ways of thinking what is cutting. There definitely is cutting involved technically but more like a machete de-limbing branches than what you would do with Mora or similar sized knife on wood, rope, etc. Technically chopping into wood with an axe or Conan knife it is also still cutting.

I don't know as much as a lot of guys about the specifics of heat treatment, carbide size and distribution, etc. but know a v edge that is thin enough to be very sharp and cut well can still be very tough. I know I've seen a lot of people comment on different knives where the machines used to sharpen at the factory leaves the edge of that knife too fragile and after a good sharpening session where you get to new metal they will do ok.
 
Yeah, as far as the chopping/slicing, I guess it's just terminology and I know what you mean.

In regards to the fragile bit, then - yup, that's exactly what I was talking about earlier, but my point about convex excelling was about the lack of the shoulders which v-edges have. The convex geometry carves as well as a scandi but it maintains its edge much better.
 
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As a swordsman swings a katana he also pulls the sword toward him in a slicing motion. It's more cutting then chopping. To me, chopping is swinging a bladed tool without pulling it in a slicing motion. So yes katanas are meant to cut, not chop.

To the point, I agree that the thinness of the edge is more important then the grind for shear cutting performance. Even if there was a difference in performance between the two it will be slight. However, durability of the edge for a given thinness of blade is important like stoffi said and that's where convexed edges shine. A super thin v grind is not going to be as durable as a convexed edge of the same thinness.
 
stoffi said:
Yes, I'm talking about angles, comparing v-edge, scandi and convex at the same angle.

No, there is a difference given the same thickness behind the edge and the same edge angle (same blade). I'll give you an example. I live in Sweden and have an abundance of Moras and whatnot at my disposal, so I've done a lot of comparing and testing. I've convexed a LOT of factory-made scandis because they ALWAYS roll if you carve with them. They come with too keen of an edge. So, I either back the angle ever so slightly or I convex them. No edge roll. Same cutting performance (in practical terms). If we're talking theoretically then they would actually be less sharp as I've made the edge more blunt, so what you're saying about heat treats and whatnot applies to my statement, as it goes without saying. I adjust the edge to convex because it works well. All of my Moras, Hultafors etc. are now even more extreme at zero-ground convex and they don't roll, whereas they all did before with the scandi-grind. Yes, they are thinner and therefor cut better, but I've also slightly convexed the bevel on scandis, as most knifemakers do here (handsharpened) and then they don't roll either and in all practical terms my slightly convexed bevels and the original ones are the same dimensions. Convex works for bushcraft because it makes the edge stronger (less acute, shorter point), yet surgical sharpness is traded in for the cutting ability of a scandi after 2 minutes of carving. I would never convex my straight razors because I understand the advantage of the v-edge as it is always sharper (more acute at same angle), but that sharpness at it's most extreme (no edge roll on given HT, steel, whatever) won't last in bushcraft with a v-edge as well as convex does at no edge roll on same steel etc.

I'd love to know how many of the people that have posted in this thread actually do bushcraft with all the edge types discussed, because that's what I'm all about and I've used more knives in the field than I can remember. I leave my cardboard cutters v-edge or scandi and make my bushcraft blades convex for several reasons. Bushcraft isn't about pen on paper theory, where v-edge wins in sharpness, it's about what works and convex really does. Why the hell would Katanas have convex grinds on swords made to fight armor and saber grinds when meant to cut flesh exclusively? Compare that with knives where wood is a tough tester. It's old knowhow and there's nothing complicated about it. It just so happens that the convex edge or zero-grind works on knives exceptionally well, but it's not as cheap to produce so the knife world has become dominated by v-type-edges, so most people haven't handled convex knives enough to fully understand what they excel at. They're not just for axes.
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You are still talking about a steel, HT and HRC hardness issues, not pure cutting performance.

If the edge doesn't hold up then there is a problem that will need to be compensated for.... Enter the convex edge to compensate for the lack of strength..... That goes right back again to Steel, HT and HRC issues.


There is no way to talk around the given issue at hand, the edge is either strong enough or it's not, if it's not then there is a problem.

I usually don't get into things about bushcraft, but there is so much complete BS that has come out of it that this time I am.

The bottom line here is that when we compensate we always give up something else in return, there is just no way around it.
 
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Buzzbait said:
I understand what hardheart is saying. If you strictly look at the math, and ignore any part that the shape of the shoulder of the edge bevel might play, there appears to be little difference in performance between a convex and a v-grind. The math may even indicate better performance from a v-grind.

I will make a couple of comments though.

  • I think that the shape of the shoulder of the edge bevel might play a more significant role, based on the substrate to be cut. What works best for cardboard, may not be best for leather or wood or rope.
  • Depth is also an issue. One has to account for the wedging action created by a full convex ground blade, helping to spread apart the substrate, thus decreasing overall friction between the blade and the substrate. To a lesser extent. To a far lesser extent, this may even occur with just a convex ground edge bevel.
  • We can't assume that we're always cutting straight into the substrate at a 90 degree angle. Some of my best uses for a convex grind are when shaving and shaping wood. I find a convex grind to be easier to control at odd angles.

I'm probably forgetting a few things, but these factors just happen to stick out to me right this moment.
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I agree that a blanket statement about performance cannot be made.

The shape of the shoulder may have an effect, and possibly as crimsonfalcon posted. Full convex grinds are recommended in choppers because they reduce the area in contact with the wood by having the grind curve outward from the centerline and provide tangential contact. A v-bevel could do similarly by reducing contact to only the shoulder transition. this would actually reduce friction if compared to a greater contact area. The tangential contact with a small convex edge surface and the contact at the shoulder of a v-bevel, what is the difference in forces? Do we actually know the amount of friction and the areas of the blade face contacted for various materials?

Depth is very important. For a stiff material like wood, a crack propagates in front of the cutting edge as the thickness of the blade cross section penetrating the wood increases. The angle will dictate how much of the downward force translates to pressure at the cutting edge through the vertical component and how much translates to horizontal wedging action. The wedging action forces the material apart, and is also going to affect frictional forces. You have the forces in the direction of the cut, perpendicular to this, and parallel to the blade surface. The grind angles will affect the distribution of forces.

Ease of control and better referencing are very valid points. I think these combine with comments of greater ease in sharpening to contribute to the idea that convex edges are sharper/stronger/etc. An edge that is easier to sharpen will probably come off the stones sharper since it takes less time/precision to maintain. In that, a convex edge is sharper, but only because the user was more readily able to get there. I would ask if anyone thinks a convex edge is sharper than one applied by Ben Dale on the Edge Pro. Also, ease of control in a cut would lead to better, more efficient cuts. Again, not so much ultimate sharpness, but practical use of the knife. Is the edge sharper, or just easier to use for some people?

If a v-bevel is converted to convex, as many people in this thread have stated to do, then the edge angle may b reduced, maintained, or increased. If the edge angle is reduced, the thickness is also reduced, and you differ from a v-bevel on both. If the angle is maintained, then the thickness is still reduced. If the angle is increased, then the thickness at a given height from the apex is also increased. So yes, a convex edge can be thinner, thicker, stronger, and more keen... just not all at the same time.
 
marcinek said:
It's kind of pointless to have a knife discussion forum if you aren't going to niggle over detail about knives, isn't it? :D
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Sure. I meant it's more irrelevant to the issue at stake. If you can't maintain the edge, it doesn't matter if it's "better" than another kind of edge. If you're trying to choose an edge, there's not much more to say than choose the edge type that's easiest for you to maintain. I'm fine with maintaining v-edges, after I had some tips. I'm not as good with convex for whatever reason. So most of my edges will be v-edges, except for choppers. But someone like Jerry Fisk who can do amazing convex edges might have a totally different story.
 
Ankerson,

I'm not debating your logic. If you read closely, you'll find that I actually agree with most of what you're saying. However, for testing purposes, it doesn't matter what heat treat or steel it is if I'm using the exact same blade for the different grinds. So we're kind of talking around eachother.

What I'm saying is that in an example where lets say the scandi's factory edge is rolling, the slight reduction of edge acuteness stops the edge rolling, yet with a zero-convex mod with the same "less acute angle" on the same blade, the blade is now thinner, so it cuts better (yes, less strong blade if you're gonna pry with it). So yes, the edge must be less acute to stop rolling (regardless of grind type), but since the shoulders are off, the knife still cuts just as well as the original scandi grind. This performance pertains to v-edge convex modification as well, but is less noticeable. On paper, the v-edge and scandi should win, and they do in terms of sharpness both in practical and theoretical terms (newly sharpened), but not many razor sharp knives will stay razor sharp (i.e. shave your beard) after a short session on some hardwood. The convex however, does not suffer from the result of dulling as much as v-edges in bushcraft, as it has no shoulders and therefor boosts the cut anyway. This is my point. If you're cutting meat or veggies where dulling isn't an issue, then the sharpness of the v-edge is unmatched, because it is grippier (pointier) and sharper; but for a trusty performance in wood... enter the convex.

Hardheart,

in response to your last paragraph "thinner, thicker, stronger..." I agree with you. However, the sacrifice of overall blade strength is so negligible in comparison to the increased and longer-term cutting performance when convexing a v-edge or scandi. It doesn't matter if the convex looses its razor sharpness or even starts to feel a little bit dull, because it'll still cut quite well because of the geometry.
 
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Ankerson said:
Exactly correct. :)
The only real benefit of convex edge is in choppers due to the added strength of the edge under impact, other than that they are a complete waste of time and effort and offer no benefit over a V edge.
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This doesn't make sense for me. If I have V grind knife, and actually remove material from the sides, it becomes stronger?
 
A.L. said:
This doesn't make sense for me. If I have V grind knife, and actually remove material from the sides, it becomes stronger?
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You aren't removing more metal making it thinner, the edge is really thicker with a higher angle (steeper) than a comparable V edge, that's were the strengh comes from.

The 2 benefits of convex in choppers are strength and with a full convex grind and edge they bind less (Stick) when chopping.
 
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