Convex or Concave Edges: Which and Why?

[SpyderEdgeForever]

I know we have discussed topics of this sort before, in regards to preferred sharpening, but I'm wondering what you all like and some of the reasons behind it: Do you prefer knife and tool edges to be convex or concave, or V Ground? And under what conditions and uses do you go with one or the other?

I admit, I tend to lean towards a convex grind because of the edge and blade strength it offers, but, there are uses that would favor a concave grind. Example: You would want a razor to be concave, or hollow ground, as opposed to convex or saber ground, right?

I have heard and read it said that if properly made, a hollow ground knife can give one years or service and not prematurely break. Hatchets and axes tend to be convex.

Another reason: Black Jack Knives website has an interesting mini tutorial and explanation on convex vs V grind blades.

http://www.blackjackknives.com/?BISKIT= ... =cat&cat=5

After looking that over, is their info pretty accurate, that the major advent of V ground blades and hollow ground blades came with the grinding machines of the industrial revolution?

[El Gato]

While this topic can be highly subjective to personal opinion, in my experience and for me personally the convex grind and edge, when properly done, makes a very fine working knife in my opinion. However, the key words here are "when properly done", and in my experience this is a rare combination to find. Please dig out your 2016 Spyderco catalog and turn to page 142, Blade Grinds. Take a hard look at the Hamaguri or Appleseed grind and this is the grind and edge that made Bill Moran famous.

Note that the grind goes from the spine all the way to the edge in a gentle flowing curve, like a good canoe is shaped midway to bow. Then a nice convex edge is applied at the end of that long gentle curve making for a very sharp and efficient cutting blade. What I am trying to demonstrate is that the entire blade is convex ground and not just the edge portion. From what I have seen too many blades are just flat pieces of steel with only the edge convex ground and this defeats the whole purpose in my experience. A well done convex edge is just not enough. It takes a properly shaped convex blade as well. Otherwise one just gets a variation of the saber grind with a convex edge and not the graceful canoe shape of the proper convex grind.

This is kind of one of those things where, "I know what I mean, but can you see what I mean?", and if I had my little Hunter made by my good friend Harvey Dean then I could show you what I mean. Gets complicated...........

Dave

[SpyderNut]

While this topic can be highly subjective to personal opinion, in my experience and for me personally the convex grind and edge, when properly done, makes a very fine working knife in my opinion. However, the key words here are "when properly done", and in my experience this is a rare combination to find. Please dig out your 2016 Spyderco catalog and turn to page 142, Blade Grinds. Take a hard look at the Hamaguri or Appleseed grind and this is the grind and edge that made Bill Moran famous.

Note that the grind goes from the spine all the way to the edge in a gentle flowing curve, like a good canoe is shaped midway to bow. Then a nice convex edge is applied at the end of that long gentle curve making for a very sharp and efficient cutting blade. What I am trying to demonstrate is that the entire blade is convex ground and not just the edge portion. From what I have seen too many blades are just flat pieces of steel with only the edge convex ground and this defeats the whole purpose in my experience. A well done convex edge is just not enough. It takes a properly shaped convex blade as well. Otherwise one just gets a variation of the saber grind with a convex edge and not the graceful canoe shape of the proper convex grind.

This is kind of one of those things where, "I know what I mean, but can you see what I mean?", and if I had my little Hunter made by my good friend Harvey Dean then I could show you what I mean. Gets complicated...........

Dave

Very well said. :)

[paladin]

Convex primary with "V" secondary...what?!???!!??

Yup...boogered up the point on my Kiwi, so it motivated me to take my extra coarse DMT + mineral spirits and grind away the hollow, finished with various sandpapers by hand...it was very therapeutic grinding away for a couple hours...I like the natural curve I put on the primary just foolin around...decided to put a 40 deg V on the edge, just because....just because grinding with my Sharpmaker is very Zen also! :) :spyder: :)

Performing like a champ on envelopes and USPS Priority Mail boxes ...

[SpyderEdgeForever]

This is a related question: I saw this knife for sale: It is the "Rough Rider Bandito Hunter". It looks to be similar to the Black Jack Classic Knives model, one of their models. The blade looks sortof convex. It is under 20 dollars. Is this a good deal? It LOOKS good in this video on Youtube here, and it slices through paper cleanly:

https://youtu.be/vivUvtW3gVQ

Based on that video does that look like a good knife, cosmetically and functionally, with that nice-looking convex edge blade? Would you buy one and use it for hunting, fishing, and other uses?

[SpyderEdgeForever]

Here is another header I came up with for this thread:

" This post is not meant to start a "family war" within the family of Spyderco users n collectors. But I will say this, in my opinion, I hold an inherent dislike and aversion to concave and hollow ground blades. Whenever I am reading a knife's description and I see anything like concave or hollow grind or hollow ground, the word "Weak Snappable Blade" immediately overtakes my mind. Now, I trust that the hollow ground knives Spyderco makes are an exception to this rule, and I am sure one could say that any decent quality knife company could make a strong hollow ground blade. But, where do you all stand on this?

I prefer the Spyderco Saber and Convex ground blades like the Scandi/Scandinavian and Zero Ground blades. The Apple Seed Grind I believe is perfect and cannot be improved upon, as an example.

And what would take this discussion to the next level: Take a hollow ground Endura and a Saber ground Endura or other convex vs concave Spyderco blades and let's put em through some severe stress tests. I would almost guarantee the convex and saber ground and appleseed ground blades would be able to take more of what can be thrown at them than the concave hollow ground blades."

[Dr. Snubnose]

While this topic can be highly subjective to personal opinion, in my experience and for me personally the convex grind and edge, when properly done, makes a very fine working knife in my opinion. However, the key words here are "when properly done", and in my experience this is a rare combination to find. Please dig out your 2016 Spyderco catalog and turn to page 142, Blade Grinds. Take a hard look at the Hamaguri or Appleseed grind and this is the grind and edge that made Bill Moran famous.

Note that the grind goes from the spine all the way to the edge in a gentle flowing curve, like a good canoe is shaped midway to bow. Then a nice convex edge is applied at the end of that long gentle curve making for a very sharp and efficient cutting blade. What I am trying to demonstrate is that the entire blade is convex ground and not just the edge portion. From what I have seen too many blades are just flat pieces of steel with only the edge convex ground and this defeats the whole purpose in my experience. A well done convex edge is just not enough. It takes a properly shaped convex blade as well. Otherwise one just gets a variation of the saber grind with a convex edge and not the graceful canoe shape of the proper convex grind.

This is kind of one of those things where, "I know what I mean, but can you see what I mean?", and if I had my little Hunter made by my good friend Harvey Dean then I could show you what I mean. Gets complicated...........

Dave

+1...Well said....Doc:)

[awa54]

a convex grind applied to the *edge* of any grind blade is essentially doing the same thing as the secondary, or "micro bevel" that you get by using the 30 deg. side to do your primary edge bevel and the 40 deg. side for the final/micro bevel on the SM. It's pretty much impossible to do any other way than freehand or on a slack belt (grinder). Convex micro bevels can be applied with a strop and aggressive enough compound as well.

A *full* convex grind like El Gato described is a whole other animal and much harder to add to a knife that has any other grind, if there is plenty of extra blade stock you could re-grind most FFG or flat/sabre ground knives to something closely approximating a true convex.

If you want to stay true to your Scandinavian knife, *don't* try to apply a convex edge bevel! They are intended to have a flat primary bevel that is uninterrupted from the top of the edge grind to the actual apex. This makes your blade function as your sharpening angle guide; you lay the bevel flat on a stone and work the edge as a whole... this makes for insanely acute edges, though they're also not all that strong. If you don't mistreat them or leave them too long between sharpenings, it's all good, but if you ding the edge badly or let it get truly blunt, it can take a lot of work to get back to the correct geometry. That said, some Scandi knives come with a micro/secondary bevel and many people choose to sharpen them that way. It works, but misses the point of the whole edge design.

Straight razors have a hollow grind to facilitate sharpening and to give the blade strength with the thick spine. Again, the straight is its own sharpening jig, but when you lay the spine and edge on your stone only those two small areas contact the surface. The final bevel on a straight is flat "V" shaped, and stropping a straight is mostly done to burnish and deburr the edge IIRC.


In any case the appleseed/convex is great for everything except ultimate edge thinness, but excels at chopping or push cutting in to hard media without wedging or sticking, FFG is a good compromise and hollow grinds are best for delicate acute blades that need to be thin behind the edge to do their job. I believe that hollow gets used on lots of commercial knives as the default because it's easy to do on grinding wheels, which are less prone to wear than the sanding belts which are needed to do FFG and convex grinds.

I used to lust after the Tormek sharpening system, but decided that a 10" wheel grinder would apply too weak an edge, due to the radius of the hollow grind it applies. That and they're darned expensive!

[Bloke]

I’ve often pondered if the true “V” edge actually exists? :confused:

I’ve found that when you free hand, your edge comes off the stone convex. Maybe only ever so slightly, but convex non the less. The same can be said for the SharpMaker! If you choose to use a micro bevel as well and intend to strop you’ve just laid the foundation for a convex edge.

Lansky’s, EdgePro’s etc. leave you with as close to a “V” as you’re likely to get, that is, till you strop or steel the edge, then it too becomes convex.
I have many Scandi Grind knives I take to a “zero” edge without a micro bevel. The fact that I’ll strop between sharpenings turns that edge convex too.

I hope I haven’t opened up a can of worms! These are simply my observations and there is nothing to say I’m not cock-eyed! :rolleyes:

[Echo63]

I use a variety of edges.

To me, the knife itself matters more than than the edge type.
I am looking for a knife that is lefty friendly, comfortable, well built and with decent steel.
To sharpen, i prefer knives with a normal "V grind" that i can easily sit and sharpen with my edgepro and easily touch up with my sharpmaker.
I do have a dragonfly i convexed, and a few BRKT convexes too.
I do love the way convex blades cut, but i dislike maintaining them - its a skill i havent really learnt yet (going to try and make a few flexible strops for the edgepro though)

[Larry_Mott]

I’ve often pondered if the true “V” edge actually exists? :confused:

I’ve found that when you free hand, your edge comes off the stone convex. Maybe only ever so slightly, but convex non the less. The same can be said for the SharpMaker! If you choose to use a micro bevel as well and intend to strop you’ve just laid the foundation for a convex edge.

Lansky’s, EdgePro’s etc. leave you with as close to a “V” as you’re likely to get, that is, till you strop or steel the edge, then it too becomes convex.
I have many Scandi Grind knives I take to a “zero” edge without a micro bevel. The fact that I’ll strop between sharpenings turns that edge convex too.

I hope I haven’t opened up a can of worms! These are simply my observations and there is nothing to say I’m not cock-eyed! :rolleyes:

IMO you nailed it there.

[The Deacon]

I’ve often pondered if the true “V” edge actually exists? :confused:

I’ve found that when you free hand, your edge comes off the stone convex. Maybe only ever so slightly, but convex non the less. The same can be said for the SharpMaker! If you choose to use a micro bevel as well and intend to strop you’ve just laid the foundation for a convex edge.

Lansky’s, EdgePro’s etc. leave you with as close to a “V” as you’re likely to get, that is, till you strop or steel the edge, then it too becomes convex.
I have many Scandi Grind knives I take to a “zero” edge without a micro bevel. The fact that I’ll strop between sharpenings turns that edge convex too.

I hope I haven’t opened up a can of worms! These are simply my observations and there is nothing to say I’m not cock-eyed! :rolleyes:

I suspect you are correct. I'm sure my freehand sharpening creates a somewhat convex edge and I'd be more surprised if Spyderco's slack belt sharpening created a perfect V than if it too was convex.

Less sure how anyone would achieve a concave edge unless it was with a "zero edge" hollow grind and, as with the "perfect V", it probably wouldn't last long.

[awa54]

I’ve often pondered if the true “V” edge actually exists? :confused:

I’ve found that when you free hand, your edge comes off the stone convex. Maybe only ever so slightly, but convex non the less. The same can be said for the SharpMaker! If you choose to use a micro bevel as well and intend to strop you’ve just laid the foundation for a convex edge.

Lansky’s, EdgePro’s etc. leave you with as close to a “V” as you’re likely to get, that is, till you strop or steel the edge, then it too becomes convex.
I have many Scandi Grind knives I take to a “zero” edge without a micro bevel. The fact that I’ll strop between sharpenings turns that edge convex too.

I hope I haven’t opened up a can of worms! These are simply my observations and there is nothing to say I’m not cock-eyed! :rolleyes:

I suspect you are correct. I'm sure my freehand sharpening creates a somewhat convex edge and I'd be more surprised if Spyderco's slack belt sharpening created a perfect V than if it too was convex.

Less sure how anyone would achieve a concave edge unless it was with a "zero edge" hollow grind and, as with the "perfect V", it probably wouldn't last long.

As far as concave edges, an edge ground on a round grinding wheel will have a concave shape, large enough wheels are very close to flat, but smaller wheels produce an obvious hollow.

Are Spyderco blades really sharpened on a slack belt? from my experience I'd guess either a backed, or well tensioned belt was used, as they don't show any rounding of the outer bevel transitions.