Why an edge bevel and why not more convex grinds.

H

Houlahound

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Aug 2, 2017
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Why not grind the blade right from wherever the first grind line starts to the edge without a secondary bevel?

Why do primary grind lines start anywhere from near the edge to the spine, what determines this?

Convex grind is clearly the strongest so why is there nearly always hollow or variations of flat grinds.

Thanx in advance.
 
Houlahound said:
Why not grind the blade right from wherever the first grind line starts to the edge without a secondary bevel?

Why do primary grind lines start anywhere from near the edge to the spine, what determines this?

Convex grind is clearly the strongest so why is there nearly always hollow or variations of flat grinds.

Thanx in advance.
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Some makers do. For instance most scandi grinds and adventure sworn do some pretty amazing convex grinds. Really it is more of a looks thing in IMO it's more about blending the edge in with the grind.
 
Not an expert, but my understanding is that convex is more time-consuming and therefore more costly to produce. Also not as easy to maintain in the field.
 
Convex grind is not clearly the strongest. There's pages and pages of very detailed debate about that.

Convex is also more troublesome to sharpen.
 
Eli Chaps said:
Convex grind is not clearly the strongest. There's pages and pages of very detailed debate about that.

Convex is also more troublesome to sharpen.
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It's quite easy to sharpen.
I mail it to Japan with insurance and tracking.
They carefully polish it with finger stones.
In 2-3 months I have it back and it only costs $50/inch.
Otherwise what are you going to do? Put a small secondary bevel on it, and sharpen it yourself?
 
Any hand sharpening produces some level of convex. The notion that convex is stronger is slightly exaggerated. Technically it should be, but in the real world I've not really noticed it making a huge difference.

Sometimes its said that convex improves cutting, but what helps cutting ability the most is narrowing down the bevel, and convex acts more like a blended micro bevel. A micro bevel can be acheived without convex if its needed.

Edit: I was rambling, fixed it.
 
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Richard338 said:
It's quite easy to sharpen.
I mail it to Japan with insurance and tracking.
They carefully polish it with finger stones.
In 2-3 months I have it back and it only costs $50/inch.
Otherwise what are you going to do? Put a small secondary bevel on it, and sharpen it yourself?
Click to expand...

You can sharpen convex yourself without a secondary but like I said, it's more troublesome. Some folks use slack belts on powered sanders, sandpaper on mouse pads, KME with convex attachment, etc.

I just don't buy them. :)
 
Eli Chaps said:
You can sharpen convex yourself without a secondary but like I said, it's more troublesome. Some folks use slack belts on powered sanders, sandpaper on mouse pads, KME with convex attachment, etc.

I just don't buy them. :)
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Do you have any experience with the KME convex rod? I'm wondering if it actually works. I have the KME system and a bunch of barkies.
 
nextcity said:
Do you have any experience with the KME convex rod? I'm wondering if it actually works. I have the KME system and a bunch of barkies.
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Sorry, I do not. I also have a KME but like I said, I don't do convex so never had a need to buy the rod. I've seen good reviews about it though.
 
Sandpaper or various grits laid over a semi-soft surface is all you need to sharpen convex edges. It is also quite tolerant to not maintaining the same angle when pulling on the blade, as the sandaper will contour to the edge according to the angle AND pressure you exert on it. It will also polish beaituflly over a loaded strop if you like that sort of thing.

Mikel
 
Houlahound said:
Why not grind the blade right from wherever the first grind line starts to the edge without a secondary bevel?

Why do primary grind lines start anywhere from near the edge to the spine, what determines this?
Click to expand...
If you make a knife with true full flat grind, it will have no secondary bevel or flat area(basically a narrow triangle if you take a cross section view). It's just a matter of geometry, purpose of use, ease of maintaining or market preference.

Houlahound said:
Convex grind is clearly the strongest so why is there nearly always hollow or variations of flat grinds.

Thanx in advance.
Click to expand...

1) Convex grind is often used for axe, and it's for good reason--it is good at splitting. And depending on geometry of the knife, most may prefer the knife grind to be 'thinner' for slicing/cutting ability rather than 'splitting'

2) Again, depending on geometry, imagine you've chipped an edge of a full convex grind knife, you will need to remove a lot of material in order to restore that edge; whereas if it's a hollow grind, since it is thinner behind the edge, you may not need to remove as much material to repair it.
 
I’ve not had any problems with the conventional beveled edge with a slight micro bevel at the very leading edge on a hollow grind. Then I don’t do much chopping or any battening with any knife. I strongly disagree with your interpretation of the strongest edge as each type of edge is for a different tool.
 
The devil's all in the details. Long story short, in most cases it's harder to manufacture and doesn't afford meaningful benefit for the context of use. There are exceptions to that, but there's a lot of confusion and hullabaloo made about convex geometries, both in the primary grind and in the edge itself. Mostly, it doesn't matter as much as other factors.
 
I'm not a fan of saying that convex grinds are for axes and hollow grinds are for thin edges, etc. How heavy the blade is and how thin the grind is matters more than the grind type. For example, many Japanese kitchen knives have very thin convex grinds on them. They typically still sharpen the edges with a flat secondary bevel.
 
Edge bevel <> grind

Using the terms interchangeably just leads to confusion.

Short answers are 1) changes in modern mass production lead to today's common grinds and 2) most people don't bother to learn how to sharpen by hand.

Buy an Opinel.
 
One advantage of an edge bevel over full flat or convex grinds is that you don't have to sharpen the entire blade flat, just the bevel.
 
It seems to me that convexing a v grind works out real well but trying to make a V grind or put a secondary bevel on a convex/ scandi grind kind of comes out like crap.

Most of my blades with a secondary bevel get convexed over time and my convex grinds have a bit of a micro-bevel because I sharpen by hand usually with a 4-5" pocket stone.
 
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