Having showed all the pros I would point out one thing. Convexing an edge that wasn't born convexed will reduce material thickness near the edge.
Cutting ability will be improved but the edge itself will be weaker.
"Will reduce material thickness near the edge"?
So if I thin the whole blade, then thin my V edge to a more closed angle,
do I get to call this a "Convex edge"?
The persisting problem with all the convex edge misinformation is that a convex edge is "thinner"... For a final time, if you have thinner edge than the V edge's shoulder, you are comparing a
thinner edge to a
thicker edge, and convexing has
nothing to do with the edge being thinner...
On the contrary, the Japanese sword makers who used a convex edge on their sword called the edge "meat in the edge",
because they understood that, all else being equal, a convex edge means, for one final time, MORE metal in the edge, NEVER less...
The Japanese concept for this is "Hiraniku" and it literally means "edge or surface meat".
HANIKU = The
meat or bevel of the cutting surface. Meaning: Convex edge.
HIRANIKU = The
meat or bevel of the whole cutting surface. Meaning: Zero edge full main bevel height Convexing.
Hamugiri meant an even thicker "clamshell edge", for the point bevel and other extreme impact edge use...
The Japanese did this because it allowed a stronger more battle-resistant edge, and moreover the lack of edge shoulder bevel fitted with wrapping up polishing and sharpening into one single process. Polishing being seen by them as an important rust prevention measure on carbon steels...: We cared less about cosmetics, so we used less maintenance-intensive V edges...
So please do as the Japanese did and get a
correct basic understanding of what convexing means, which is that,
all else being equal, an edge becomes a
thicker edge with convexing...
A V edge will
always be thinner than a comparable convex edge,
below the equal thickness measuring point. That V edges are usually ground much thicker is testament to a V edge's superiority, because if
convex edges, on Bark River knives for instance, were to be ground that thick, the knife would become completely useless, and customers would intent lawsuits against knife companies...
V edges allow most makers to get away with much thicker bevels... 0.040" and beyond... And on big fixed blades, boy do they ever go for it... I've even seen 0.060" on some high end custom stuff...
Then people will compare this to a convex edge that is 0.015" at the equivalent distance, and say, "see? Convex edges perform
better"...
As to a convex grind reducing friction to a single line on each side, this supposedly reducing friction... Well... If you reduce the surface of contact you
increase the friction... The reason axes are convexed is because the fattening of the blade allows a more intense
splitting action, and this does allow separating the fibrous wood material ahead of the edge,
assuming it is not a cross-grain cut, which does save edge wear on an axe.
Unfortunately for all the potential applications of this to knives, knives do not have the weight momentum to waste energy into greater friction to create greater lateral splitting forces: Knives have to chop wood instead with finesse and deep penetration.
This is even more evident if you do cross-grain cutting, where grain splitting is even less of a factor...
A huge disadvantage of the fatter convexed edge, all else being equal, is that you can't hit the bottom of a previous hit as you chop: The fatter edge gets "pinched" by the sides of the previous impact, and so instead of hitting the bottom of a previous slice
hard, and deepening the slice, the blade gradually decelerates, robbing it of any ability to deepen the previous cut: This forces you to "spread" your hits wider to avoid hitting the same spot twice: Note how the better geometry here allowed the Lile to be used on a narrower area, while the convexed Trailmaster, not much thicker edged, forced me to spread the hits much wider and also performed miserably in comparison...: The Lile weights 16.9 ounces, the Randall around 20 and the SMIII Trailmaster 17 ounces...
Gaston
