To me convex is more about no abrupt shoulder transition and bevel curvature. Curvature where could be optimize for max flow through material - think what shape a submarine/bullet/airplane-wing/etc yup mostly convex. Clear as mud

"I read a comment once where the writer had claimed the convex grind or rolled edge has less friction because it only contacts on a tangential point. This would be true if only the material being cut has no give, no movement, no springiness to it. Also, as that material is cut, it would just open up, not pinch, but contact rigidly at one single point. But just what material would that be?"

Hey Mark
I loved your blogs on the convex edge, excellent work my friend!
I wonder if this isn't good spot to pop in a little history of the convex edge.
It is probably the oldest method of sharpening around. Even in the early times of metal blades a la the bronze age, the easiest method of sharpening for the common fellow was to sit in his camp during the early evening passing his blade edge along a handy stone of suitable hardness creating or rebuilding the sharpest edge he could manage in the simplest way available. Another time stopping by a rocky stream tumbling down a mountain side for a drink, he might pause in his travels and again work on that edge. As Ken pointed out, a convex edge is a bit of a cheat since it is impossible to guarantee the angle when sharpening this way manually, but eventually the edge would obtain that wonderful bullet shape ogive that gives one a substantial edge for heavy duty tasks...for this bronze age fellow chopping wood, blazing a trail through those ancient tractless forests, killing and rendering after hunting down some animal or another and lets not forget self defense, for cleaving through bone and armour when the occasion arose.
For the guy who sharpens by hand , it is the natural product of sharpening and stropping manually daily, eventually the convex edge will appear.
Using the modern tools like the WEPS as Mark has described so beautifully in his blog, makes the building of this kind of well supported edge an easy task and it can be maintained easily and for a long time simply by stropping on something handy, be it a piece of leather with or without compound,on your jeans, a piece of sandpaper or even a piece of newsprint. Using any of these will keep that excellent round shoulder and ogive sharp and ready for cutting, slicing, chopping and whatever. Hopefully though, not for cleaving through armour and the bones of enemies! LOL!
So down through the ages the convex edge has been the useful companion of the ordinary man, simple and reliable...not always super sharp at first, but eventually through daily stropping, it becomes a strong and very sharp edge. An axe is an excellent tool that utilizes a convex edge and one can see in this useful tool a convex edge working at its strongest and finest.
Enough? I guess so, I do go on yes?

Leo

Enough? I guess so, I do go on yes?

Leo

BluntCut wrote:


When you are talking about the shapes you mention, keep this in mind, thos designs are done using fluid dynamics as the basis. We typically are not cutting fluids nor gasses. The sharpest things I know of, microtome blades and obsidian scalples, used to part relatively soft solid material very cleanly and with low effort, they do not use a convex edge.

[...]

What contributes most to the amount of friction encountered in cutting is the
actual blade grind rather then the bevel... or so I think. This would be true especially when cutting anything with a thickness that is an appreciable percentage of the blade height.

Yes, your explanation is clear as mud... but I think I got what you said anyway...

Thanks for moderating, Ken. I'll recommend you to Clay .

BluntCut wrote:


Very interesting, Bluntcut and Philip.

I know little about fluid dynamics and how it compares to friction in a solid material (if anyone can explain me, that'd be great), but what strikes me is that indeed for cutting relatively soft materials (food, tissue) a V-bevel is usually preferred. And for cutting hard material (wood with an axe or an outdoor knife)) a convex bevel seems preferred.