V edge on a convex

J

Jonnygomes

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Jul 10, 2017
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Hello, I'm wondering if it's alright to put a regular edge on a knife that was (is) a convex edge ? Appreciate any feedback ,thanks.
 
Jonnygomes said:
Hello, I'm wondering if it's alright to put a regular edge on a knife that was (is) a convex edge ? Appreciate any feedback ,thanks.
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Hi mate, yes there's no problem at all doing that. It just takes time and some good old fashion elbow grease. I've done it to dozens of knives. Just pick your angle, mark the edge with a sharpie and take it slow until you grind away the convex outward curve and hit the apex. Take it slow and keep checking regularly. Rinse and repeat on the other side. Much easier done on a guided clamp system such as a wicked edge, edge pro, KME etc. with some diamond stones.
 
It's totally fine. If the edge apex is equal then you'll just eventually be wearing a "flat" (really just less convex unless using a jig) into the bevels as you sharpen your way back into them and will eventually just need to knock the shoulders off to keep cutting performance equivalent.
 
After years of sharpening convex edges I've come to the conclusion it's easier to do on bench stones. Once the curve of the blade has been shaped by the stone I simply add a small bevel. I usually start with a 1000 grit waterstone to set the secondary bevel then finish with a 2-5k stone.

IMO, it's faster, easier, and gives performance identical to other methods.
 
Basically I took a 22 degree angle to my fallkniven f1 and it cuts pretty good . I just didn't feel right doing it ,not sure exactly why but I'm glad to hear that it's acceptable
 
Personally, aside from a microbevel to finish off the edge I'd leave it as a convex. To keep it as thin overall after being converted, you almost have to go back and flatten out the sides, or the cutting bevel will be less acute than it aught to be.

Once you start grinding it back, you're essentially doing more work that it would have taken to maintain the convex.
 
HeavyHanded said:
Personally, aside from a microbevel to finish off the edge I'd leave it as a convex. To keep it as thin overall after being converted, you almost have to go back and flatten out the sides, or the cutting bevel will be less acute than it aught to be.

Once you start grinding it back, you're essentially doing more work that it would have taken to maintain the convex.
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Best advice there.^

Odds are, the existing convex edge is already relatively wide in angle. Taking it back to a V-edged profile will either necessitate doing a lot of thinning behind the edge to keep the edge angle reasonably acute and sharp, OR adding a microbevel at what will be an even slightly wider angle than it's at now. Short-term, the microbevel is the easiest to do, but may not be as sharp. Longer-term, I'd consider keeping it as a convex overall, but gradually thinning it out over time, either on stones as Jason B. recommends, or with an edge-trailing 'stropping' technique on firmly-backed sandpaper.

If you're lucky, and the existing convex isn't too thick now, then just using conventional sharpening techniques for V-edges will likely be the best approach. To be sharp in the first place, at least a tiny bit of the grind immediately behind the apex will need to finish with essentially a 'V' shape anyway, in order to ensure a crisp apex. An edge that's obviously convex all the way out to the apex is likely to be very wide in apex angle and less sharp, or even rounded or blunt.


David
 
While I can agree with Heavy, especially his last sentence. And if it's a customers try to keep it original looking. With 'Bush Craft' being in vogue
many like that style... I'd have to really examine it and deliberate over it whether I'd change it to a V grid. DM
 
Well, given that for a certain apex angle the convex is then reducing in angle the farther you move back from the edge, putting a V on a convex won't really reduce how penetrating the edge is until you've worn back into the bevel by a fairly good margin, and even then it's still a thinner geometry than if you'd done the same thing with a V bevel.

Basically, if your edge is thicker than it should be, make it thinner. Use appropriately coarse stones for the task and it won't take you long. No need to overcomplicate it--just think about your desired edge angle and sharpen at that. If the edge isn't hitting the stone, just use a coarse stone to keep working the bevel at that angle until it contacts the stone like it should, then progress. Don't bother getting caught up in the whole convex vs. flat thing because that's comparatively unimportant and more of an "icing on the cake" consideration. Your real primary concern should simply be "is the geometry as thin as I want it?"
 
I just put a v edge on it and blend the shoulder into the primary.
Any freehand sharpening has some convexing to it anyways.

If the edge is too thick then I make a more acute secondary and blend it.

If it's too thin then microbevel.
 
42, if it's just going to be my knife I would do it. And I have done it on a Buck 119 & 103 and 120. Using a coarse stone not diamond but a coarse SiC. You can create a good V or really thin it out so it will slice and skin well. But be sure that's what you want because once you squirt the toothpaste out of the tube, it's difficult to get it back in. DM
 
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