What's tougher a scandi or convex edge?

[Shotgun]

Define "edge angle" please. I have defined it above. Where are you confused?

I'll try and clear this up as you're not wrong, your just starting with a different definition of what an edge angle is. Imagine a 40 degree angle. If your knife fits within that angle to where the apex of your knife edge is touching the apex of the the angle, then your edge is 40 degrees or less. A convex edge doesn't bulge out, it curves inward gradually upping the edge angle until it terminates. Your diagram in A isn't what I would consider a good convex because it's seems to bulge out in the middle and then seems to come back toward being flat. A good convex IMO should start out relatively flat and then increase in curvature as it gets closer to the edge. That means the apex would have the highest edge angle.

 

[FortyTwoBlades]

I'll try and clear this up as you're not wrong, your just starting with a different definition of what an edge angle is. Imagine a 40 degree angle. If your knife fits within that edge angle to where the apex of your knife edge is touching the apex of the the edge angle, then your edge is 40 degrees or less. A convex edge doesn't bulge out, it curves inward gradually upping the edge angle until it terminates. Your diagram in A isn't what I would consider a good convex because it's seems to bulge out in the middle and then seems to come back toward being flat. A good convex IMO should start out relatively flat and then increase in curvature as it gets closer to the edge. That means the apex would have the highest edge angle.

Yes yes yes! That's one of the things I'm trying to explain through diagrams right now. Pain in the but, but as they say a picture is worth...well, something at least!

Just remember that with the above explanation that, presuming equal edge angle on each side, you'd (of course) have a 20° angle per side or less. This is stating the obvious, but it's important to keep in mind when discussing sharpening angle.

 

[Joe Duder]

I hate to even mention it, but as one who has gone from grinding Hollow, to grinding Flat, to now mostly grinding Convex;

...the shape of a Convex bevel can vary in shape depending on the intended use.


This thread seems tied up in semantics, and both side are easily argued.


The point of my intrusion is that the shape and nature of a Convex grind is another variable that adds to how an edge performs at a given task.


You can have a fat bottomed Convex edge that can be as tough as an axe, or thin the point of that Appleseed to where it's slicie-slicie, or, of course, anywhere in between.


Hollow grinds (defined my wheel diameter) and Flat grinds (flat by definition) offer limited options to the maker, and are popular because of there ease of manufacture. But a Convex edge offers much more flexibility in how the finished product can performing different intended uses.


There's no doubt that a super slim, flat ground blade, hand made and heat treated for max performance by an expert knife maker, can be a great performer. But this thread is about Convex Vs. Scandi, and I think the OP has figured out what he wanted to know.


Trying to argue about knives without using them is pretty silly to start with.

Any well made knife can work well.

My advice would be to spend more time using knives, and form you own opinions.




Big Mike

I know what works for me and I do have my own opinions. I started this thread to try and get both sides, through a amicable discussion. Well things went south somewhere. Perhaps the blade world's vocabulary is filled with too much duality and if not, maybe it's definitions are easily misunderstood. I don't know.

I'll be the first to admit- I'm no blade dictionary master.

I thought my question was simple, but I'm learning that there aren't many simple questions and answers in the blade world.

 

[FortyTwoBlades]

It's something ultimately very very simple, but also very very hard to describe.

 

[FortyTwoBlades]

In the following diagrams, the rectangle is the virgin bar stock, and the vertical dotted line is the central plane of the bar.

Here we have a full flat zero grind--the most irreducibly simplistic and uniform measurement for a knife ground from bar stock. No complicated curves to worry about, and the grind goes straight from one edge of the spine down to the centerline of the stock. Only a hollow grind could get thinner without reducing the spine thickness. Since truly hollow edges are nearly impossible for a typical user to preserve in their purest form, for all practical purposes, the approximately 7° angle shown here is the thinnest edge angle you can reasonably produce without thinning the spine.


Here we have a more conventional full flat grind with "V" or linear edge. The angles are exaggerated from what you would really typically see just for ease of viewing. On the right you see a convexed edge of equal effective angle. Note the volume of green that's been lopped off by this. A small reduction, but in practical use it's noticeable.


Here's a full flat grind in its original form and the bevel created by sharpening it waaaaaaaay back at the exact same angle. The fuchsia indicates the original length of the bevel--it was literally copy/pasted, shifted vertically, and color swapped. It's the exact same "piece" of bevel as the green original one. The orange represents the elongation of the visual bevel height cause by the sharpening. You can also see the massive reduction in primary bevel height.


This is a "polygonal" representation (again, with angles exaggerated so you can see it easier) that quasi-replicates a full convex grind. You could do all the math you wanted on this one since each section is a measurable volume of a rectangle with an inferable triangle pegged on the side. The effect is the same though--you can keep on taking shorter/thinner paths from the edge of the spine to the centerline until you hit the full flat zero grind of the original diagram again, and then start hollowing it out until you end up with nothing but a "T" that'll just crumple up on itself and not cut ANYTHING.


So all this argument is pretty academic. Thinner cuts easier, but it isn't as strong. Thicker is tougher, but has to displace more material over a shorter given unit of distance so it doesn't cut as well. Even if the aforementioned "T"-sectioned knife didn't crumple up (on account of being made out of "rostafrei" ) it'd just cut GREAT--practically falling through the target--until it hit the spine, and then it'd stop due to suddenly having to displace the full width of the spine over an incredibly mega-tiny distance.

 

[Ankerson]

I'll try and clear this up as you're not wrong, your just starting with a different definition of what an edge angle is. Imagine a 40 degree angle. If your knife fits within that angle to where the apex of your knife edge is touching the apex of the the angle, then your edge is 40 degrees or less. A convex edge doesn't bulge out, it curves inward gradually upping the edge angle until it terminates. Your diagram in A isn't what I would consider a good convex because it's seems to bulge out in the middle and then seems to come back toward being flat. A good convex IMO should start out relatively flat and then increase in curvature as it gets closer to the edge. That means the apex would have the highest edge angle.

Yes, exactly correct. :thumbup:

 

[Jason B.]

I don't understand why every convex discussion is so confusing. You always get the two diagrams with one showing a thicker convex when its just not possible unless the blade starts off thicker. I'm no good at math and can't do trig yet still understand that 99.9% of convex vs V edge drawings posted are incorrect.

Convex is only stronger because you see it done on thicker blades. When most convex a edge they raise the angle while thinning the back bevel thus creating the perception that its stronger.

You get better performance from a convex edge sharpened to the same apex angle because you thinned the back bevel and a rounded surface has less points of contact.

It's pretty simple really, you just can't add metal in sharpening, convexing makes a thinner edge.

 

[FortyTwoBlades]

I don't understand why every convex discussion is so confusing. You always get the two diagrams with one showing a thicker convex when its just not possible unless the blade starts off thicker. I'm no good at math and can't do trig yet still understand that 99.9% of convex vs V edge drawings posted are incorrect.

Convex is only stronger because you see it done on thicker blades. When most convex a edge they raise the angle while thinning the back bevel thus creating the perception that its stronger.

You get better performance from a convex edge sharpened to the same apex angle because you thinned the back bevel and a rounded surface has less points of contact.

It's pretty simple really, you just can't add metal in sharpening, convexing makes a thinner edge.

Here's a pic I did up a while back addressing just that point. :thumbup:

 

[Gossman Knives]

Here's a pic I did up a while back addressing just that point. :thumbup:

This is a perfect drawing explaining the convex edge not the primary grind. Most of the confusion with "convexing" comes from when someone is asking about the edge not the primary grind. The primary grind with a zero secondary bevel that is convexed does have a curvature from spine to edge in one continuest flow. Just like most axes have.
The drawing above shows a flat primary grind with a secondary V bevel that has had the shoulders rounded off giving you a convexed "edge".
Scott

 

[FortyTwoBlades]

This is a perfect drawing explaining the convex edge not the primary grind. Most of the confusion with "convexing" comes from when someone is asking about the edge not the primary grind. The primary grind with a zero secondary bevel that is convexed does have a curvature from spine to edge in one continuest flow. Just like most axes have.
The drawing above shows a flat primary grind with a secondary V bevel that has had the shoulders rounded off giving you a convexed "edge".
Scott

Precisely. It's fairly uncommon for someone to truly be asking about the grind itself, and even in circumstances where a knife has a convex primary, many of them have a linear edge bevel--such as Opinels and Svords. In the case of the primary grind a full height zeroed convex grind will, indeed, have more material to it than a zeroed full flat grind, but a zeroed full flat grind is incredibly rare to find due to edge fragility caused by such a low angle. The variable nature of a convex and/or full flat grind means that a full height zeroed convex could be either thicker or thinner than a full flat grind with a secondary bevel depending on how they're done. Again, it comes down to how circuitous a route you take from the spine to the centerline.

 

[Ankerson]

I don't understand why every convex discussion is so confusing. You always get the two diagrams with one showing a thicker convex when its just not possible unless the blade starts off thicker. I'm no good at math and can't do trig yet still understand that 99.9% of convex vs V edge drawings posted are incorrect.

It's because they are parroting what they have been told and the marketing BS along with the fact they just don't understand what is really going on with the angles....

They are told or have read that a convex is stronger so it has to be thicker right?

It's only confusing because of the marketing BS that is spread in an effort to sell more knives and people buy into that crap and actually believe it......

 

[Mikael W]

It's because they are parroting what they have been told and the marketing BS along with the fact they just don't understand what is really going on with the angles....

They are told or have read that a convex is stronger so it has to be thicker right?

It's only confusing because of the marketing BS that is spread in an effort to sell more knives and people buy into that crap and actually believe it......

This is not my experience and I beg to disagree!


Regards
Mikael

 

[Ankerson]

This is not my experience and I beg to disagree!


Regards
Mikael

There have been countless threads just here on BF alone and a lot of the posts go along exactly with what I just posted and are completely incorrect.

I have a lot of full convex grind blades here (Mainly Busse) and some with convex edges also..... And it just doesn't work the way people are told it does.

 

[Mikael W]

There have been countless threads just here on BF alone and a lot of the posts go along exactly with what I just posted and are completely incorrect.

I have a lot of full convex grind blades here (Mainly Busse) and some with convex edges also..... And it just doesn't work the way people are told it does.

I'm perfectly allright with this opinion, but as I do my own convexing on my users, I have to say convex works for me.
I'm aware of the differrence between a full convex and a convexed edge and I also have both, but they are not made by Busse.

BTW, those Phil Wilson's of Yours are totally awesome!



Regards
Mikael

 

[marcinek]

It's because they are parroting what they have been told and the marketing BS along with the fact they just don't understand what is really going on with the angles....

They are told or have read that a convex is stronger so it has to be thicker right?

It's only confusing because of the marketing BS that is spread in an effort to sell more knives and people buy into that crap and actually believe it......

Thank you. Precisely what I said in post #14...only much more direct. :thumbup: And thanks FortyTwoBlades for a much better picture than the one I posted earlier....a simple drawing doesn't lie.

Let me add that I prefer convex ground blades, and I knock the shoulders off my flat ground blades. But I know it makes them have less steel behind the edge. And I know it doesn't make them sharper (another claim of the certain convexed-knife makers)....it makes their sharpness easier to maintain for me.

I know that certain convexed edge knife makers are under the impression that they are omnipotent and their knife making skills allow them to transcend the laws of mathematics and physics...but it's just not true.

It all goes back to this: draw a vee. Draw a convex edge inside that vee. Those two edges have the same edge angle. The convex is thinner behind the edge.

 

[Big Mike]

It's because they are parroting what they have been told and the marketing BS along with the fact they just don't understand what is really going on with the angles....

They are told or have read that a convex is stronger so it has to be thicker right?

It's only confusing because of the marketing BS that is spread in an effort to sell more knives and people buy into that crap and actually believe it......

This is not my experience and I beg to disagree!


Regards
Mikael

I agree with Mikael, my personal experience is what matters to me.


The point that's being missed in this discussion is that there is room for all types of different grinds and edges.

Find the edge that works for the task at hand and you'll be a happy camper.


There's no wrong or right in this discussion, we all strive for better performing knives.

Personally, I tweak every knife I have until it performs to my satisfaction.

As I stated earlier in this thread, debating the subject is fine, but getting out and trying different grinds and edges is the best way to figure it out for yourself.




Big Mike

 

[Mikael W]

It all goes back to this: draw a vee. Draw a convex edge inside that vee. Those two edges have the same edge angle. The convex is thinner behind the edge.

John, it depends on how You design that convex!

Have a look at the Vee on Your Mora Clipper.

If You just knock of the shoulders and convex them, then I understand Your thinking.
You have certainly added to the slicing capacity of the Clipper.

If You also convex the very cutting edge by removing steel, You get more steel to support the edge.
The bladeheight will decrease, but the edge will be stronger.


Regards
Mikael

 

[marcinek]

I agree with Mikael, my personal experience is what matters to me.


The point that's being missed in this discussion is that there is room for all types of different grinds and edges.

Find the edge that works for the task at hand and you'll be a happy camper.

Of course there is. But the subject at hand is what grind is stronger. And if by stronger we are talking about amount of material behind the edge, than for a given edge angle, "flat" has more material behind the edge.

And people doing things like making up new definitions of "angle" or, in effect, saying "Hey look at that!" and pointing to attempt to change the subject don't make that simple picture FortyTwoBlades posted go away.

 

[gine]

Here's a pic I did up a while back addressing just that point. :thumbup:

Nice diagram, however I believe you have shown two extremes. A true convex is curved all the way to the edge. In your diagram on the right, you show the convex curve flattening out. In actuality a convex maintains it's curvature all the way to the center point. The halfway point between your two diagrams would be a more accurate description.

 

[marcinek]

John, it depends on how You design that convex!

Have a look at the Vee on Your Mora Clipper.

If You just knock of the shoulders and convex them, then I understand Your thinking.
You have certainly added to the slicing capacity of the Clipper.

If You also convex the very cutting edge by removing steel, You get more steel to support the edge.
The bladeheight will decrease, but the edge will be stronger.


Regards
Mikael

Agreed. And you get a larger edge angle when you convex the edge like that. And a vee grind with that same, new edge angle will have more steel behind the edge than that convex.