Does a Convex Bevel Require a Convex Edge? Is It Tricky to Set a Convex Edge?

[redsquid2]

Just thinking here. I don't have any knives with convex bevels. I am wondering: Does a convex bevel need to just be one continuous bevel all the way to the edge? I read somewhere that you have to have a mousepad to set a convex edge. That sounds complicated. Is there anything wrong with taking a convex bevel, and then setting a flat edge on it?

Thanks.

Andy

 

[Obsessed with Edges]

Just thinking here. I don't have any knives with convex bevels. I am wondering: Does a convex bevel need to just be one continuous bevel all the way to the edge? I read somewhere that you have to have a mousepad to set a convex edge. That sounds complicated. Is there anything wrong with taking a convex bevel, and then setting a flat edge on it?

Thanks.

Andy

Nothing at all wrong with that. I think most purists might like to keep it convex all the way to the edge (and that can have advantages), but a blade with a convex primary grind can work just fine with a standard 'V' secondary or micro-bevel. Many factory 'convex' blades actually have a small V-secondary or micro bevel anyway, from the start. I think most people would find it easier to maintain a V-bevel at the edge, using some of the more common tools like a Sharpmaker, for example. That is, at least until they've had time to practice with convexing. Convex sharpening is essentially identical to 'stropping' technique (edge-trailing stroke). So, if you've become pretty adept at that, it's just a matter of 'stropping' your edge at a coarser grit, using sandpaper on a somewhat forgiving backing. Once you get that technique down, I think you might even find it even easier than V-bevel maintenance techniques (I did; it's my favorite method now).

The greatest advantage of convex is the 'smooth' or 'rounded' shoulders of the bevel, which really reduces the resistance encountered in cutting thicker or tougher material, such as heavy leather, cardboard, and even wood. The geometry of the cutting edge itself still needs to be very 'sharp', obviously. That means that even on a convex blade, the edge itself still is essentially a very pure 'V', if it's going to cut very well at all. Too much 'convex' (rounding), taken all the way to the cutting edge, would result in an edge that will be very thick, and probably blunt as well. My favorite means to 'convex' a blade is to set a very clean & pure V-bevel with a guided setup (I use a Lansky or DMT Aligner), and then 'convex' the hard shoulders of the new V-bevel, by 'stropping' on sandpaper (on firm leather-over-hardwood) at a conservatively low angle. The edge itself remains unaltered, for the most part, if I do it 'right'.

 

[OHALLUM]

David, you just explained in one paragraph, and quite well I might add about all you need to know about convex edges. Someone else would probably have to write a book trying to do the same explanation. My hat is off to you and your knowledge of these subjects. What a great forum with all the combined knowledge available on here.

Omar

 

[dantzk8]

The greatest advantage of convex is the 'smooth' or 'rounded' shoulders of the bevel, which really reduces the resistance encountered in cutting thicker or tougher material, such as heavy leather, cardboard, and even wood. The geometry of the cutting edge itself still needs to be very 'sharp', obviously. That means that even on a convex blade, the edge itself still is essentially a very pure 'V', if it's going to cut very well at all. Too much 'convex' (rounding), taken all the way to the cutting edge, would result in an edge that will be very thick, and probably blunt as well.

Very true. The best way to convex an edge is to sharpen freehand on a stone trying to keep the bevels as flat as possible. Try this test: whittle a piece of wood. If your edge is too much convexed your blade will be pushed away from the wood. Correctly ground, you will keep control of the cut and will get a flat cut. Who needs a sharpened spoon?

dantzk.

 

[Bigfattyt]

I have found convex edges the easiest to maintain out of any I've encountered.

They just seem really easy to set, and maintain with no skill freehand.

I took a group of scouts a while ago, and showed them sand paper over a soft backing (only about a 10 minute explanation to the boys). One boy took his knife to hair popping sharp all on his own with just the mousepad and paper I gave him. No further instruction, and just an old leather belt to strop on. That knife had a Franken bevel on it before he started too!

 

[Obsessed with Edges]

David, you just explained in one paragraph, and quite well I might add about all you need to know about convex edges. Someone else would probably have to write a book trying to do the same explanation. My hat is off to you and your knowledge of these subjects. What a great forum with all the combined knowledge available on here.

Omar

You're very welcome, Omar.

What I mentioned, about the technique being essentially identical to stropping; I just can't emphasize that strongly enough. When I really got into sharpening, I 'obsessed' over learning stropping technique for a while. I was stropping all the time, after using my Lansky setup to re-bevel a whole bunch of knives. There came a point, one day, when it just 'occurred' to me to lay a piece of wet/dry sandpaper over my strop block, and do the exact same thing I'd been doing. And voila! A very neatly convexed edge bevel on my blade was the result. I was thrilled, and amazed at how easy it really is. I've never looked back, and this is how I maintain & touch up my blades (aside from stropping, which is usually all they need). About the only time I use hard hones/stones anymore, is if I want to change the edge angle significantly (I always go more acute, when doing this). I'll use the guided setup for that, to re-set the bevels, and then use medium-to-high grit wet/dry paper to smooth out the shoulders.

 

[awestib]

... About the only time I use hard hones/stones anymore, is if I want to change the edge angle significantly (I always go more acute, when doing this). I'll use the guided setup for that, to re-set the bevels, and then use medium-to-high grit wet/dry paper to smooth out the shoulders.

David, that reminds me of what virtuovice does with his hunting knives on youtube. He grinds the bevel down quite aggressively and acute if the bevel is too thick and/or obtuse for him and then he puts a convex "Microbevel" on it. In his experience of skinning dears and touching bones, this is enough to keep the edge from failing. I tried something similiar on a true scandi edge (so stropped microbevel) and it indeed increases the strenght of the edge quite a bit without loosing significant bite!!

 

[redsquid2]

Well, it is nice to know it's not that hard to make a convex edge.

Do you hold the blade at the same angle you normally would with a stone? I normally go for 20 deg. per side, 40 deg. inclusive, so do I go about it the same way with the sandpaper and mouse pad?

Thanks for all the replies.

 

[Obsessed with Edges]

Well, it is nice to know it's not that hard to make a convex edge.

Do you hold the blade at the same angle you normally would with a stone? I normally go for 20 deg. per side, 40 deg. inclusive, so do I go about it the same way with the sandpaper and mouse pad?

Thanks for all the replies.

Since convexing involves using a softer backing (usually), like leather or a mousepad, it's best to keep the angle conservatively low. The softer backing will compress a little bit, and that will tend to make the sandpaper 'wrap around' the edge a little bit, if the angle is a little to steep, or if pressure is too heavy. That will result in the edge getting rounded off or blunted. So, keep the angle a little lower than you would do on stones, and keep pressure very light.

Use a Sharpie to darken a portion of your blade near the edge (maybe 1/4" wide, from the edge up). Pay close attention to where the ink comes off the blade, as you work. That'll give you a better feel for the 'correct' angle. Check frequently for improvement in the sharpness of the edge, and for the formation of a burr.