Convex or V edge ?

I put a convex edge on all of my knives with the exception of my Spyderco's. I find it improves the performance of the knife when cutting through wood as there is less of a 'shoulder between the edge and the rest of the blade, reducing drag. Having a fully convexed blade improves things still further when cutting deeply into hard material like wood. I also like reprofiling with a convex edge using the mousemat method. The reason being you can use a magic marker to simply mark where you'd like the new edge to finish and then work on coarse(ish) paper until the pen is removed and voila. No jigs, special gadgets, etc:)
 
hardheart said:
Tf the two edges are the same thickness with different geometry behind them, then they do not have the same sharpening angle. A convex grind is thinner than a v-bevel for the same final included angle. That is the difference.

Do you have any force measurements showing a difference between v-bevels and convex? There is precious little friction at the transition between edge and primary grind.

After numerous delays, my planned CATRA experiment is moving forward again, albeit with some adjustments. We will be testing different angles, grit finishes, thicknesses, etc, but I cannot include convex edges until I get a consensus on how to apply it. I asked about it right here on BF and we didn't get far. When the amount of convexity can be easily measured and equally applied by many, then we can get better data. As for now, my fully convexed edges don't appear to work any differently in regular cutting than my v-bevels, even though applied with jigs or clamp systems.
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Exactly correct. :)

In real use there really isn't a noticeable difference in cutting as long as the blades are sharp with the correct angle ect.

Stropping and freehand sharpening will give a slight convex over time.

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.

Anyone who says they can tell the difference in normal cutting between convex and V edges is living in a dream world and is delusional at best......

It's one of the biggest myths and urban legends in the knife world.
 
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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.
 
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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Edge angle and thickness of the blade behind the edge has more to do with cutting efficiency than any other factor, the rest is a given such as edge finish, sharpness ect.

The thinner the blade is behind the edge the better and easier it will cut and move through the material.
 
Ankerson said:
Exactly correct. :)

In real use there really isn't a noticeable difference in cutting as long as the blades are sharp with the correct angle ect.

Stropping and freehand sharpening will give a slight convex over time.

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.

Anyone who says they can tell the difference in normal cutting between convex and V edges is living in a dream world and is delusional at best......

It's one of the biggest myths and urban legends in the knife world.
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Single best thing I've read on any knife forum in a long time. Well put!

I will add this though. I prefer convex. My convex edged knives cut better than my v ground knives. Because I can maintain convex edges better. That's the only reason. But this whole thing about there being some mystical, magical, geometric properties of convex edges is merely hype from certain manufacturers of convexed knives.
 
I only sharpen with the Sharpmaker, so the result is a V ground edge. This works well and is the easiest for me to do. I don't get these super, super, sharp edges, the ones that carve hair, but I get sharp enough edges for what I need. But this summer I received two knives, a fixed blade Browning Crowell/Barker Competition Cutter, and a folder, the Lion Steel SR-1 V. Both have a convex edge, and are the first knives I've had with this type of edge. I will say that this convex edge is sharp, really sharp. I'm going to have to do some reading to see how I need to maintain the egdes.

As far as what is best..............???
 
Poez said:
Than what is the point of having that discussion? Than there is no such thing as convex grind, there is only poorly done V grind. :D
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Convex grind is the primary blade grind and that will make a huge difference especially in choppers.
 
cutter17 said:
I only sharpen with the Sharpmaker, so the result is a V ground edge. This works well and is the easiest for me to do. I don't get these super, super, sharp edges, the ones that carve hair, but I get sharp enough edges for what I need.
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Precisely my point. To get those super, super sharp edges on a v grind you need to maintain an exact angle. Which is hard to do on a Sharpmaker. Or any freehand method (unless one is very, very good at it).

I'd love to hear back from you later when you get the convex thing down (its really simple....just don't overthink it). I bet you will be getting those super, super, sharp edges, because convexing takes advantage of that "blade angle play" that is keeping you from getting those super, super sharp v grind edges.

But again, its not because a well maintained convex grind is better or sharper than a well maintained v grind, it's because a well maintained convex grind is better and sharper than an average to poorly maintained v grind. And I know I don't have the skill (or the setup) to do a top-notch job maintaining a v grind. I get the feeling a lot of people are in the same situation as me.
 
Here is all the knowledge you need to get scary sharp edges on the Sharpmaker using a V-grind. Micro Bevel. Just sharpen the blade at a smaller angle than the desired Sharpmaker slot setting. You can do this on pretty much any coarse stone, DMT, India, King water stone, etc. Then go to the Sharpmaker. Voila, hair whittling edges right off the standard white stones, or even gray if you practice.
 
OK, I'm talking bushcraft and not surgery here:

A convex edge is never as pointy (sharp) as a v-edge at the same angle, yet it has less resistance in cutting, making it cut pretty much the same; but not in surgery or shaving though.

The main drawback of v-edges is the shoulder between the edge and the primary grind. Yes, one can take it down and have a really sharp v-edge with very little shoulders, but then the convex zero grind or even the convex edge excels, as it won't be as pointy (minimizing edge roll and chipping) and it has less friction. Also, I often find that I slip on the shoulder of a v-edge while carving wood, whereas with a convex or scandi I don't. Basically, if you take a convex, a v-edge and a scandi to the same angle of your average scandi, then the convex won't be as sharp (pointy) as the other two, but it will have less resistance in the cut and therefor act as if it was just as sharp, but they'll all cut with different characteristics, i.e. the wood slicings will curve differently for each knife. I pretty much convex everything because it offers a less acute edge, which won't roll as easily yet it feels just as sharp as equivalent angled knives while cutting wood, because it has a streamlined geometry. It's sort of like comparing cars: a Porsche has a lot more horsies than a Lotus Exige, yet the Exige will rip the Porsches heart out because it's lighter. So it's never about just one thing - it's about taking everything into consideration. The Porsche can pull a wagon better, but the Exige will give you more Gs. A v-edge or scandi will shave better but loose their acute sharpness quick, whereas the convex will have it's slightly less sharp edge longer and still cut pretty much the same after each represented knife edge has cut 30 times, because it has more metal backing that edge and it's streamlined, so it boosts the cut, making it perform sharper than what it is.
 
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stoffi said:
OK, I'm talking bushcraft and not surgery here:

A convex edge is never as pointy (sharp) as a v-edge at the same angle, yet it has less resistance in cutting, making it cut pretty much the same; but not in surgery or shaving though.

The main drawback of v-edges is the shoulder between the edge and the primary grind. Yes, one can take it down and have a really sharp v-edge with very little shoulders, but then the convex zero grind or even the convex edge excels, as it won't be as pointy (minimizing edge roll and chipping) and it has less friction. Also, I often find that I slip on the shoulder of a v-edge while carving wood, whereas with a convex or scandi I don't. Basically, if you take a convex, a v-edge and a scandi to the same angle of your average scandi, then the convex won't be as sharp (pointy) as the other two, but it will have less resistance in the cut and therefor act as if it was just as sharp, but they'll all cut with different characteristics, i.e. the wood slicings will curve differently for each knife. I pretty much convex everything because it offers a less acute edge, which won't roll as easily yet it feels just as sharp as equivalent angled knives while cutting wood, because it has a streamlined geometry. Also, I like the look of a shiny zero ground blade.
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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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I dunno but my convex knives are stupid easy to get back to screaming sharp with nothing more than a scrap of sand paper and my thigh. I have been edc'ing a David Farmer custom FB that's only about 8 OAL and I have a new appreciation for what a full convex with convex edge is capable of. And as always for me, maintenance/ease of maintenance is a big factor to consider. I don't have any clamp systems and my free-hand techniques will get the job done but won't win any photo contests for perfect edges and (for me) takes a heck of a lot longer to get right.
 
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:)
 
I'm seeing a couple different lines of thought here. The folks that think that convex is going to cut better think that the shoulder of a v-edge somehow creates extra drag or friction against the material. I'm not really sure I understand the logic of that; it seems likely to me that you'd be just as likely to have more material pressed against a convex edge because it's easier for the material to mold itself against the rounder shape, than a shoulder, and the less material you have making contact, the lower the frictional force.

But I kinda think that's beside the point, because in both cases, said frictional force is going to be negligible, especially with regards to cutting ability. What makes a knife able to cut better than another are the angle geometry of the edge along with how much you have behind the edge. Those of you who are thinking that your knives cut better when you put a convex edge on them aren't thinking about the fact that when you do that, you change the edge angle. If you really wanted to demonstrate that your convex knife cuts better, then you'd need to convex an edge precisely at the same angle and thickness as a v-edge, and compare those 2. I'm willing to bet that the difference is negligible.

Honestly, all of the niggling over details is rather irrelevant. If you can't do a reasonably good job of maintaining a v-edge, and you end up convexing it, then you're probably better off with convex. But even though you may convex your edge SOMEWHAT with sharpening, I personally find that I have a tougher time maintaining my edge geometry and keeping a sharp edge on a convex edge than on a v-edge. YMMV. If you can get a good convex edge and maintain it, for a CAMPING knife that you may chop with, that's probably best. But if you can't maintain one type of edge as well as another, it's really a tautological question, isn't it?
 
Brian Sargent said:
I also maintain my Scandis with sandpaper. Simple.

I think it is a myth that you can free hand and maintain a perfectly flat V bevel. You will have some amount of convexing to it.

It's safe to say that you didn't really read what I typed.
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Sure I did, I just don't agree with you.

One can maintain any edge if they know how. It is always skill over gear. Sandpaper and a flat surface is all you need for a Scandi or V bevel.

Also don't agree that convex cuts better than V bevel, there's so much more to it than that. They both perform and perform well if the user knows what they are doing. Goes back to skills over gear.
 
avoidspam said:
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.
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You are comparing apples and Buicks.

(Your Opinel is convex, by the way. But its so thin that convex vs v is pretty academic. Which I beleive backs up Ankerson's claim.)
 
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