-
The BladeForums.com 2024 Traditional Knife is available! Price is $250 ea (shipped within CONUS).
Order here: https://www.bladeforums.com/help/2024-traditional/
Convex grinds
- Thread starter JJaggar
- Start date
Others far more knowledgeable than I can probably explain more thoroughly, but picture the cross section of the knife looking like an apple seed. Each side of the blade curves in a convex arc down to the edge.
The main advantage is that there's plenty of steel backing up the edge so that it's very strong. The disadvantage is that it can be tougher to sharpen.
The main advantage is that there's plenty of steel backing up the edge so that it's very strong. The disadvantage is that it can be tougher to sharpen.
- Joined
- Dec 30, 2005
- Messages
- 1,051
Actually a v grind of comparable angle has MORE steel behind the edge. The "convex has more steel thing" is nonsense. I have a pretty strong suspicion where it originates. Sorry. Geometry doesn't lie.
As far as maintenance...I find they are EASIER to maintain. It takes advantage of not being able to hand hold an exact edge eangle consistently, and can be made/maintained with a few bucks worth of simple materials. Some wet/dry sandpaper, a piece of leather, and a flat surface is really all you need.
As far as maintenance...I find they are EASIER to maintain. It takes advantage of not being able to hand hold an exact edge eangle consistently, and can be made/maintained with a few bucks worth of simple materials. Some wet/dry sandpaper, a piece of leather, and a flat surface is really all you need.
If you free hand sharpen a knife on a wet stone it will turn into a convex edge because people simply cannot repeat the same stroke over and over that many times. No worries, the convex edge is sharper and stronger. It is hte main reason those in the know change the profile on all their knives and make the convex. Many of the truly best knife designers and manufactures only produce convex edges.
You can use a belt sander, sand paper and a mouse pad, or wet stones to sharpen your knife.
You can use a belt sander, sand paper and a mouse pad, or wet stones to sharpen your knife.
- Joined
- Apr 3, 2011
- Messages
- 5,949
Actually a v grind of comparable angle has MORE steel behind the edge. The "convex has more steel thing" is nonsense. I have a pretty strong suspicion where it originates. Sorry. Geometry doesn't lie.
As far as maintenance...I find they are EASIER to maintain. It takes advantage of not being able to hand hold an exact edge eangle consistently, and can be made/maintained with a few bucks worth of simple materials. Some wet/dry sandpaper, a piece of leather, and a flat surface is really all you need.
what a perfect visual... great job marcinek. i totally agree. so what happens is that you have increased cutting ability (slightly) due to the shoulders being knocked off/rounded.
A convex edge doesn't have an angle; it has two intersecting arcs.
Those arcs can be more or less acute than a standard V edge. A convex edge can have more or less metal behind the edge. A convex edge can be virtually identical to a V edge.
But, when you compare a convex edge to a V edge and when the shoulder widths of the two edges are the same and when the edge heights are the same, under those conditions a V edge will be more acute and a convex edge will be more robust.
In reality, we seldom know what people are talking about when they say they have a convex edge because convex edges can take an infinite number of forms. We can easily describe a V edge by measuring the edge angle and the shoulder widths of the edge. I've yet to see anyone describe a convex edge by correctly describing the arcs that form the edge and the shoulder width of the edge -- and without those measurements, you don't know what you have.
Either edge can be easy to sharpen, if you use the correct technique.
Those arcs can be more or less acute than a standard V edge. A convex edge can have more or less metal behind the edge. A convex edge can be virtually identical to a V edge.
But, when you compare a convex edge to a V edge and when the shoulder widths of the two edges are the same and when the edge heights are the same, under those conditions a V edge will be more acute and a convex edge will be more robust.
In reality, we seldom know what people are talking about when they say they have a convex edge because convex edges can take an infinite number of forms. We can easily describe a V edge by measuring the edge angle and the shoulder widths of the edge. I've yet to see anyone describe a convex edge by correctly describing the arcs that form the edge and the shoulder width of the edge -- and without those measurements, you don't know what you have.
Either edge can be easy to sharpen, if you use the correct technique.
I totally get that a convex edge has no actual bevels to it like a V Grind, i guess I just want to know much other stuff about it such as will it keep a keen edge just as long or longer than other ginds, specifically speaking about bark river here with their A2 steel as on the Ghost 2. Does anyone own a Ghost 2? Would love to hear more about convex grinds
Sure. And when you compare a v edge and a v edge with a more obtuse edge, the one with the more obtuse edge will be more robust. So what?
That is precisely what you are saying. The only way to compare the grinds is to compare grinds with matching angles. And you CAN assign an angle to a convex. Look at the tangents to the curves forming the edges at the points where the edges meet.
That's the same way you define the angle for a vee grinds. Its just that for that flat vee grind the tangents are the same as the grind.
And when you do that...like was done in my picture...you see that the convex has less behind the edge.
I know people hate geometry and calculus, but they still exist. Sorry.
The red line it tangent to the blue curve at point A.
Imagine you draw a vertical line though A and reflect the blue curve and red line across that vertical line.
Then you have a vee grind (the red lines) and a convex grind (the blue curves) that have the same edge angle. And the convex is inside the vee. And thinner.
- Joined
- Feb 3, 2006
- Messages
- 8,250
It does and it doesn't. It's an arc so you're right there's not a continuous line/angle that can be measured. However, if you draw a perpendicular line to that arc at the apex, then draw a line 90 degrees to that, that is the line that you measure from. Doing the same thing on both sides, the angle between those lines that were drawn at 90 degrees is your edge angle. From there the "angles" become more acute because the convex slowly slopes away from that original angle at the apex. So you can say that with say a 20 degrees inclusive edge angle, that a convex edge will have less metal because the curve slopes inward whereas a v grind keeps going at that angle. If you repeat the steps you did measuring the apex further down along the curve you'll see the angle shrink from 20 degrees to 0 which would then be the flat of the knife. In order to get more metal from a convex grind, you have to increase that initial angle at the apex which means the convex grind will be more obtuse and won't perform as well as the v grind.
- Joined
- Feb 3, 2006
- Messages
- 8,250
The red line it tangent to the blue curve at point A.
Imagine you draw a vertical line though A and reflect the blue curve and red line across that vertical line.
Then you have a vee grind (the red lines) and a convex grind (the blue curves) that have the same edge angle. And the convex is inside the vee. And thinner.
You're quicker than I am.
The red line it tangent to the blue curve at point A.
Imagine you draw a vertical line though A and reflect the blue curve and red line across that vertical line.
Then you have a vee grind (the red lines) and a convex grind (the blue curves) that have the same edge angle. And the convex is inside the vee. And thinner.
Mike Stewart at Bark River can design an excellent knife. And his shop can produce an excellent knife. But he cannot transcend geometry and mathematics, however much people would like to believe it.
- Joined
- Oct 28, 2013
- Messages
- 577
Marcinek,
Thanks for the illustration. That is probably a good representation of most convex edges, especially since many people convert their V edges to a convex one. It isn't representative of all blades and sharpening angles though, so you have only shown that you CANNOT make a definitive statement about whether convex/flat edges have more mass behind the edge. I think that is the point some are trying communicate.
You can't argue with geometry.
Thanks for the illustration. That is probably a good representation of most convex edges, especially since many people convert their V edges to a convex one. It isn't representative of all blades and sharpening angles though, so you have only shown that you CANNOT make a definitive statement about whether convex/flat edges have more mass behind the edge. I think that is the point some are trying communicate.
You can't argue with geometry.
We could do that, but people REALLY aren't to like THAT.
Look at my original picture and reflect the blue curve across the red tangent. Now you have a hollow grind with a 0 degree edge angle.
That isn't reality obviously. But...those red lines show the edge angle, right? See how the convex is always inside the red lines, the vee at the red lines? And the vee grind has more material behind the edge? Where is the hollow? Outside.
Thanks but it is not at all the point I am trying to make. The point I am making is that, for a vee grind, and a convex grind that have the same edge angle (the tangents at the point where the edges meet)...the vee grind has definitively more material behind the edge.
If you are not comparing the same edge angle, at you are saying is that a knife with a more obtuse edge angle has more steel behing the edge than a knife with a more acute edge angle.