can you convert the edges? And is it worth it?

williamsld8

williamsld8

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Sep 19, 2010
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can you take a regular blade like a kershaw leek or a spyderco persistence and sharpen them to become convex blades? Or is this not a good idea? And what should one keep in mind when convex sharpening, whether converting a rgular edge or just working on a knife that's produced as a convex.
 
It can be done, it is not a "bad" idea, and it is relatively easy to get a razor sharp edge this way. It all depends on your preference.
 
Sandpaper over mousepad and it will be a perfect convex. Depends on your still though.
In general, even if you sharpen on a stone, freehand, it will be convex. Human hand isn't that steady to grind straight V edge ;)
 
Gator97 said:
Sandpaper over mousepad and it will be a perfect convex. Depends on your still though.
In general, even if you sharpen on a stone, freehand, it will be convex. Human hand isn't that steady to grind straight V edge ;)
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Tell me and my middle finger that after four hours on a DMT. I use my fingers as guides and get really close to perfection, in a zen like state.
 
swamp said:
Tell me and my middle finger that after four hours on a DMT. I use my fingers as guides and get really close to perfection, in a zen like state.
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I'm telling you :p

You can do it, but the question is should you?
What would be the gain for you?
Is it easier to sharpen for you? Right for your cutting application?
 
good questions. ill answer them with questions. :D what type of applications would a convex edge triumph over a standard bevel in? so i know whether or not it would be better for me. what are the pros and cons to a convex edge? and are they easier to maintain?
 
it's pretty easy, try to be meticulous about the grind lines, and if you feel yourself getting sloppy take a break and come back to it.
 
williamsld8 said:
good questions. ill answer them with questions. :D what type of applications would a convex edge triumph over a standard bevel in? so i know whether or not it would be better for me. what are the pros and cons to a convex edge? and are they easier to maintain?
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eh. unless you're doing a lot of very fine detail work, I doubt you'd notice much of any difference in comparing something like a Kershaw with the V grind, or converted to convex edge.

The difference come more into play for how the knife is actually ground, but comparing two of the same knife would be very tough. I'd say it comes down to what you are more comfortable sharpening.
 
there's a difference too between a convex edge and fully convexing a blade. on a knife with a very thin blade (like the leek) a convex edge would work better, but i saw a video where a guy fully (well almost fully) convexed an esee 5 and i think the full convex worked very well in this thick bladed application.

it's faily easy to maintain, and pretty easy to do too. you dont HAVE to be as exact as you do with stones because the mousepad will be a little more forgiving. now i'm not saying you can be sloppy and get good results, but if you are no good at stones give convexing a try.
 
Convex edge will make a difference when cutting cardboard, especially for prolonged sessions. For sticky mediums like cheese it's also a better performer. Although, mainly it's the edge sharpness than it's shape. But given equal sharpness convex and V have their advantages.
 
The two main advantages of the convex are: 1) The edge is stronger because there is more meat behind it, and 2) the geometry of the edge lets you change directions more easily when cutting. The best edge for slicing bologna is the chisel edge (one side bevel).
 
sweet_hitch-hiker said:
there's a difference too between a convex edge and fully convexing a blade. on a knife with a very thin blade (like the leek) a convex edge would work better, but i saw a video where a guy fully (well almost fully) convexed an esee 5 and i think the full convex worked very well in this thick bladed application.

it's faily easy to maintain, and pretty easy to do too. you dont HAVE to be as exact as you do with stones because the mousepad will be a little more forgiving. now i'm not saying you can be sloppy and get good results, but if you are no good at stones give convexing a try.
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This is an important differentiation. Convexing an edge is relatively easy, convexing a blade can be a significant chore, especially without a belt sander. It will also depend on the blade thickness and original grind to determine if it is reasonable to consider convexing the entire blade in the first place.

There is tons of discussion on the merits of convex vs V bevel grind, and for certain applications I suspect each has it's strengths.

For me, I convex the edges on all my knives because I find I get the best sharpening results. But that is strictly personal preference.

A sharp knife is a good knife, and IMO the best sharpening method is the one that gives you the desired results.

As for what to consider when convex sharpening; use very little pressure against the sandpaper. Use the appropriate grit of sandpaper and let the sandpaper do the work (i.e. use very little pressure). To initially develop the convex you may need to start with 100 or even 80 grit paper, then work your way up to 600 or 900 or 1200 grit to get the level of polish you desire. Then finish with a strop. This will likely take several hours to acheive.

Go to Knives Ship Free website, or do a google search, there are dozens of videos on convex sharpening that discuss/demonstrate the theory and the technique.
http://www.knivesshipfree.com/pages/Sharpening-Videos

Kevin

RAT RC4 with the edge convexed.
DSCN1239.jpg
 
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I end up convexing most my knives.

My reason is that I find the convex the easiest edge to maintain at a very sharp level.

I find that convex edges and a strop a much quicker and less "set up" intensive than many methods.

I also strop my V edges as the final step.

I keep all my knives hair popping sharp.

You can have a thick edge or a thin edge with a convex.

You can have a convex edge that slices like a demon, or a much too thick convex edge that won't cut very well at all.

It is not the V edge or the Convex edge that makes a knife a cutter, or great chopper, a lot of it is the profile of the grind. A very thin primary grind with a steeper edge grind will still cut better than a much thicker primary grind in certain applications.

Full convex grind adds a whole different dimension to the equation as well.

I can grind you a full convex grind that chops and cuts horrible, but it will technically be a full convex.

It's all about the geometry.

Done right, a full convex grind will probably be your out right best chopper. Done wrong it will be a turd.

Seems like a lot of the comp cutters in competition are using a full flat grind to a blended convex edge.
 
I put a 'convex' edge on my kershaw Leek and Cyclone (ie: I just sharpened them with the sandpaper/mousepad technique), and I found it worked really well, especially on the Leek. I converted the cyclone back to a standard edge, but I still keep the Leek convexed.

It works REALLY well, and it's easy to maintain.
 
All my knives are convex just because I suck at any other sharpening method. I find convex is more forgiving as if you get the angle wrong you don't generally blunt the edge.
 
tiguy7 said:
The two main advantages of the convex are: 1) The edge is stronger because there is more meat behind it
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Not true, especially if we are talking about converting to convex. When you transform V to convex, you remove steel from the sides of the secondary bevel and hance making the edge portion of the blade thinner. This means that all the material at sides will pass the blade easier and make the illusion of sharper edge, but definitely making better and flowing cutting experience.
 
it's easy to mantain once you got it, to me it's not only easier but also cuts better
strop and sandpaper and you're ready

i'm slowly convexing all my V knives that get used

Maxx
 
Using pure logic...no way a convex edge can be the sharpest option.

A convexed blade would be an improvement over a flat grind for chopping though. You would have less resistance while swinging through the wood or rope. In theory you would want a thin edge followed by a slight rise at a point reached that is thicker than the object you are cutting with a thinner blade following that so the blade doesn't touch as it passes thru the object.

That is why hollow grinds are flat out the best for slicing thin material in thicknesses up to the back of the blade, or portion where the HG stops. There is no resistance after the first cut.

It is also why you releave a blade by sanding at 20 degrees and then putting a 25 degree edge on it, or 15/20 whatever you prefer for your application.

Talk to a few cheifs and ask them how important the releaf area on their knives are when they chop heavy veggies, or soft item like cheese.

If one were to convex a blade that imulated a hollow grind they might believe it was the best thing in the world. Someone the convexed a blade to match a flat grin would think it sucked if they when from a releaved edge or hollow grind.
 
Hey,

I don't convex the whole blade and I love the way that hollow grounds cut (like the leek). But I do convex the edge to about 15-18 degrees depending on the steel. I always convex the edge on all my knives on a belt sander, I have yet to get a sharper, more durable edge using any other method, but I will leave the main grind the way it is.
 
this is all great input and I thank you all very much. Now how do I know exacy what angle I am putting my edge on?
 
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