I tried convex sharpening today....

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Razorsharp-Travis

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I had a go at convex sharpening today. I folded some newspaper as a backing and put a piece of 220 grit sand paper on it and reprofiled a 440a kershaw leek to god knows what degree, ill get to you guys with the angle right at the edge tomorrow. Anyways, after 220, I skipped a few and went to 1500, got a hazy mirror edge that was decently sharp, slicing receipt papereasily, shaving well... managed to work that up to a hair splitting edge.

I never thought I could achieve that on simple SiC sandpaper. :)

Hair splitting is pretty much my standard test and I am surprised, honestly. I wonder what will happen after a few passes on denim and my 0.5u diamond loaded leather strop :p
 
How much newspaper did you fold for the backing? I think where most people screw up is they use a backing that's too thick and soft, and then use too much pressure. Sounds like you did it right. I have been using a thin peice of suede on top of my granite block, that seems to be just about right.
 
Convexing is a lot of fun, I recently did it for the first time on my sabre ground delica. Results were amazing. I used a thin rag folded in half as the backing for the sandpaper. Now ive got two dedicated mousepads, one of which I have loaded with Cr(III)O for the final stropping. Im happy with the polished edge and I love the way the tip rounds to a point. Even when the knife isnt sharp it slices decently :)

Do you guys convex to a zero edge or do you put a small microbevel on the edge??
 
I'm not sure that the phrase zero edge has much meaning when talking about convexing. If you mean putting a small V-edge on a convex grind, I don't normally do that because it would seem to defeat the purpose of the convex by creating shoulders at the base of the v-edge (though it is a quick way to field sharpen a convex edge). However, you can raise the angle a bit on your soft backing to create a steepening of the convex right at the edge. That is essentially a micro-bevel, but it flows into the curve of the grind above it, so it is not really a distinct bevel. It's just altering the shape of the curve.

Since it is can be difficult to tell what edge angle you are creating with convex sharpening (due to variables with soft backings), I do like to create a flat V-edge at a known angle and then convex-grind at the shoulders until the convex curve just meets the edge. The very edge will still be from the flat grind, so it will remain at the angle you want.
 
It's a nice feeling, isn't it? :)

I had the exact same reaction, when trying SiC sandpaper for the first time. Just seems too simple for the results produced.

Razorsharp-Travis said:
I had a go at convex sharpening today. I folded some newspaper as a backing and put a piece of 220 grit sand paper on it and reprofiled a 440a kershaw leek to god knows what degree, ill get to you guys with the angle right at the edge tomorrow. Anyways, after 220, I skipped a few and went to 1500, got a hazy mirror edge that was decently sharp, slicing receipt papereasily, shaving well... managed to work that up to a hair splitting edge.

I never thought I could achieve that on simple SiC sandpaper. :)

Hair splitting is pretty much my standard test and I am surprised, honestly. I wonder what will happen after a few passes on denim and my 0.5u diamond loaded leather strop :p
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Razorsharp-Travis said:
Stropped it... Oh man. Its taken a very sweet edge :eek:
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leafstorm said:
Convexing is a lot of fun, I recently did it for the first time on my sabre ground delica. Results were amazing. I used a thin rag folded in half as the backing for the sandpaper. Now ive got two dedicated mousepads, one of which I have loaded with Cr(III)O for the final stropping. Im happy with the polished edge and I love the way the tip rounds to a point. Even when the knife isnt sharp it slices decently :)

Do you guys convex to a zero edge or do you put a small microbevel on the edge??
Click to expand...

I 'zero' all of my convex edges (and most V-bevels, for that matter). So long as the edge isn't too extremely thin, I've never felt a need to micro bevel. In instances where I have done it, it's usually the default result of a few quick touch-up passes on a Sharpmaker or similar, when the priority is just restoring cutting effectiveness quickly, on a dull/mediocre edge. Once I have the time, and the appropriate tools at hand, I'll usually work it back down to a zero edge.
 
Robs92XJ said:
I'm not sure that the phrase zero edge has much meaning when talking about convexing. If you mean putting a small V-edge on a convex grind, I don't normally do that because it would seem to defeat the purpose of the convex by creating shoulders at the base of the v-edge (though it is a quick way to field sharpen a convex edge). However, you can raise the angle a bit on your soft backing to create a steepening of the convex right at the edge. That is essentially a micro-bevel, but it flows into the curve of the grind above it, so it is not really a distinct bevel. It's just altering the shape of the curve.
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Agreed on all accounts. Ive actually never had much success with microbevels, I just wanted to see what others thought. Both of the convex bevels on my delica meet at a 'zero edge.' As you pointed out its somewhat of a misnomer but it gets the point across that its one consistent, rounded bevel.

Robs92XJ said:
Since it is can be difficult to tell what edge angle you are creating with convex sharpening (due to variables with soft backings), I do like to create a flat V-edge at a known angle and then convex-grind at the shoulders until the convex curve just meets the edge. The very edge will still be from the flat grind, so it will remain at the angle you want.
Click to expand...

Interesting, do you mean this is how you sharpen a knife that is already convexed? Or is this the process you go through when convexing a knife that was originally V ground?
 
Obsessed with Edges said:
I 'zero' all of my convex edges (and most V-bevels, for that matter). So long as the edge isn't too extremely thin, I've never felt a need to micro bevel. In instances where I have done it, it's usually the default result of a few quick touch-up passes on a Sharpmaker or similar, when the priority is just restoring cutting effectiveness quickly, on a dull/mediocre edge. Once I have the time, and the appropriate tools at hand, I'll usually work it back down to a zero edge.
Click to expand...

Yes the 'zero' edge is the only kind ive had success with. Ive not gotten the sharpmaker to work for me yet and I can't seem to put a microbevel on a knife freehand for the life of me. I need to feel and see the edge contacting the stone. Im still pretty new to sharpening. Using the shadow between the edge and the stone has been very helpfpul for me in maintaining a given angle.

Convexing was not as difficult as I initially thought it would be either. I still cant get my knife quite shaving sharp, but everytime I sit down I find myself improving. That's all one can really hope for right!
 
leafstorm said:
Interesting, do you mean this is how you sharpen a knife that is already convexed? Or is this the process you go through when convexing a knife that was originally V ground?
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Well, that is definitely the process when you are converting a V grind to a convex, if you don't want to make the edge more obtuse.

If it's already convexed and you are happy with the edge angle, and you remember how you sharpened it last time, it's not necessary.

What I mean is, when you sharpen a 15 degree bevel on sandpaper with a soft backing and you hold the knife at 15 degrees, the very edge will be something greater than 15 degrees. How much greater depends on how soft/thick the backing is, and how much pressure you use. So if you want to keep the edge at exactly 15 degrees, you would need to hold the knife at something less than 15 degrees. Through trial and error you can figure out how much less of an angle you need. Or, you can sharpen on a flat stone at 15 degrees until the edge is formed, then work the metal behind the edge with the soft backed sandpaper so that the convex curve blends with the 15 degree flat bevel at the very edge.

It's something I might do if I had a convex knife that was too thick at the edge, and I wanted to reprofile. Or if for some reason I was trying to hit a specific edge angle. I'm not saying it's necessary, because with experience you can account for the give in the backing. But it's another approach.
 
Yah I gotcha now. It definitely is a process where 'feel' is as important as consistency. Thanks for sharing your tips, its always interesting to hear how others technique has developed!
 
I'll tell ya, for a simple no BS convex edge that gives hair popping results....the worksharp is hard to beat. Any low speed belt sander with the platen removed, for that matter will give great results. I'm not trying to sell or anything like that for the work sharp but in my opinion, it just plain works. I do think the jump from 220 to 6000 is a bit much, but since I got their 1800 SC belt, man it leaves a pretty awesome edge and it's fast. There's a bit of a learning curve to keep the tip from rounding, but practice makes perfect. I'll strop the final product with green compound and that's it. The cool thing about it is like any good sharpening, there's no need really to go back onto the machine. The strop straigtens it out and you're good to go. Unless you've done some major work or something. I will say that since I've received this (as a B-D gift), the convex edge is it for me.
 
I've heard people talking about a 'zero edge'
Is this just a phrase that means there is no micro bevel?
 
Chris Pierce said:
Would a Scandi grind be an example of a zero edge?
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Yes, a Scandi where the primary bevels meet at the point is a prime example of what has become referred to as a Zero Degree Edge,


...though I can't say the term makes much sense to me.





Big Mike
 
Big Mike said:
Yes, a Scandi where the primary bevels meet at the point is a prime example of what has become referred to as a Zero Degree Edge,


...though I can't say the term makes much sense to me.





Big Mike
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I think the term 'zero edge' implies 'zero (no) secondary bevel', as opposed to zero degrees (which wouldn't make sense to me, either).
 
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