Convex vs Stones for "soft" steels

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berzerker

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Jan 27, 2002
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I'll start by saying I know there is a long-standing debate about convexed versus angled edges, and I don't want this to become a flame war. I'd like to hear from people who've actually experimented with both on identical knives.

Now that I've built a contraption to do convexing with some accuracy, I've started to think about the following: For a "softer" steel--which could be 420HC (or something with higher carbon content, but run softer than usual)--which method (convex or angled) would provide an edge maintaining the best sharpness? The argument about putting more steel behind a convex edge suggests it might prevent edge deformation of softer steels, but does anyone have anything approach data--cutting tests, etc.

I will say that I'm planning on doing my own research with a few pairs of identical knives, but that's going to wait until after Christmas.
 
I have a few big outdoor knives that are convex. All of my other knives are flat bevelled. ("V" grind)

I personally can't tell any difference in edge holding between knives with the same steel. This is another one of those questions that will never really be answered. I always advise my friends who ask to get whichever one tickles their fancy, because both work well. :)
 
I like convex in theory, but find a v or straight edge easier to maintain freehand.
 
If you are using a strop with compound or sandpaper, sharpening a convex edge is foolproof and easy. The key is not to push too hard and don't use a mousepad, hard leather works best. The reason is that a soft mouse pad will allow the edge to push in and the abrasive will rub against it, making the blade dull. Once I figured this out I was popping hairs in no time.

As to the OPs question, flat grinds are sharper, but the actual shape of a convex makes it a more controllable slicer. The v grind is more prone to rolling, but I find this is mostly due to the very steep angles these are ground to right to the edge, there is something to the "more steel behind the edge" theory.
 
I think that softer steels are going to lose their edge fairly quickly no matter how you do it. I would suggest you go with whatever you can most quickly and easily touch up - because if you want your knife sharp you will need to resharpen pretty often.
 
winbag338 said:
Delica's, skyline's, and csk II's. Convex is it, with second place going to micro bevel.
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:p This is what I meant when I said the question will never be answered. :p

Many experienced people will agree with winbag, and many other experienced people will take the opposite stance. That always happens whenever you have two or more systems that work equally, or near equally, well.
 
berzerker said:
Now that I've built a contraption to do convexing with some accuracy, I've started to think about the following: For a "softer" steel--which could be 420HC (or something with higher carbon content, but run softer than usual)--which method (convex or angled) would provide an edge maintaining the best sharpness? The argument about putting more steel behind a convex edge suggests it might prevent edge deformation of softer steels, but does anyone have anything approach data--cutting tests, etc.
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For the same angle at the cutting edge, there is more steel behind the V edge. Sketching the two types of edges superimposed to the same scale will show this.
 
In my experience, it doesn't matter. As long as you can get it sharp, use whatever method works for you. Either way, the edge will dull with use. I conves sharpen most of my blades, and, no disrespect to Liam Ryan, but I use a mouspad, and it works great, for me. I get haip-poppin', tree-toppin' edges, and I use a lot of pressure, at first, with the courser grits, and then use less and less with the higher grits. I make sure I get a burr along the whole edge, on both sides, through 3-4 grit counts, then strop it off. That works for me. The thing I find is, now that I have figured out the geometry rquired for the edge to be sharp, now I can use stones free-hand, or guided systems, and a strop, to get at least as sharp of an edge. So, I am now experimenting with V-grinds.

I personally don't buy into the whole "convex is stronger" argument. It isn't stronger if it is at the same final angle, because to round it off at the shoulder, you remove material behind the edge. For it to be stronger, it can't be the same final angle at the terminous of the edge. Convex, then, works like having a small secondary bevel. It can still be screaming sharp, but not the same fineness of the edge. The sharpest steel objects on earth have secondary and tertiary grinds: disposable razor blades (Or, so they said on the History channel special on sharp objects.) You will have people screaming from both sides, my way is better, don't do it that way, use a mousepad, don't use a mousepad, get a burr, avoid a burr at all costs, stop with compound or without, use Chromium oxide, use diamond spray, etc., etc...

My point is, it really doesn't matter. Find what works for you, and be prepared to re-sharpen any knife, because even blades forged of super-ultra-uber unobtainium alloyed with meteorites and adamantium with triple heat-and quench cycles, will dull eventually, regardless of the edge geometry used.
 
There is the same amount of metal at the same angle coming off the edge. The differences between convex and flat bevels is macroscopic and don't affect the sub-micron edge radius that does the actual cutting. You can have a 30 degree inclusive bevel on a 1/8" stock knife, or a 30 degree bevel on a 1/4" one, the bevel is still 30 degrees, and there is the same amount of steel in the first few tenths of a millimeter, just like a thicker/thinner convex bevel doesn't change it.
 
Well I, for one, am eagerly awaiting the results of the OP's testing. Using pairs of the same knives with no difference except the edges should make for some pretty valid results.

Keep us posted!
 
MVF said:
Well I, for one, am eagerly awaiting the results of the OP's testing. Using pairs of the same knives with no difference except the edges should make for some pretty valid results.
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I'd be doubtful on that. I think whichever one you managed to do a better job of getting a sharp edge on would be better. With practice in the other method you could equal or beat whichever one worked best in the testing.

I would definitely go with whichever you could get the best results easily with.
 
Use stones to get a convex edge.
I couldn't sharpen a flat bevel if my life depended on it. All you have to do to convex the edge is grind behind the edge as much as you do on the edge (I usually use three separate angles). It's good for edge maintenance anyway, as you're always thinning out the edge for better slicing performance.
 
hardheart said:
There is the same amount of metal at the same angle coming off the edge. The differences between convex and flat bevels is macroscopic and don't affect the sub-micron edge radius that does the actual cutting. You can have a 30 degree inclusive bevel on a 1/8" stock knife, or a 30 degree bevel on a 1/4" one, the bevel is still 30 degrees, and there is the same amount of steel in the first few tenths of a millimeter, just like a thicker/thinner convex bevel doesn't change it.
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Very well stated, hh.

No doubt the convex vs. v-bevel "controversy" will continue to be argued for as long as people use knives, but IMO the choice has very little to do with edge/blade performance, and is really more a matter of preferred sharpening method and convenience, and perhaps blade aesthetics -- which are themselves valid considerations.
 
I think it comes down to the point of diminishing returns. Any difference probably wouldn't make a difference in the real world, nor be noticable.

Both edges are very similar, they accomplish the same thing, and there is a very small difference in the actual geometry.

Logically if you consider a convex having more steel behind the edge. (I doubt it's actually significantly more than a standard V) The knife will be duller.

I'll use a stropped V edge personally, it's easier to tell where you need to sharpen if you say take a chunk out. The dull spot is very obvious, and treatable, not as much for a convex imo.
 
I prefer to convex the edges / blades on most of my user knives unless they have a particularly hard steel (ZDP189, D2, etc). On these softer blades I can maintain the convex edges easily with just some cardboard and various grits of sandpaper, which means I am more likely to touch them up regularly and keep them very sharp.

I have several Victorinox and Wenger SAKs that I picked up used with badly worn (i.e. sharpened on a disc grinder) blades that I put a full convex on and they are just cutting fools. That thin blade with a sleek convex profile keeps cutting for a long time even after the shaving edge is gone.
 
I'd say do what you find the easiest,
If it's a softer steel you're going to spend more time on touch ups so the easiest way for you is the way you should do it
 
Theoretically the convex edge doesn't have a "corner" and should be a very slightly little bit more efficient.
That said, practically it really is all about what angle you sharpen at. I doubt testing would show any difference between the two edge types.
 
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