A Burr that doesn't feel like a Burr?

[mlmcasual]

---

After upgrading my sharpening stones to a complete range of Shaptons, from 320 to 5000 grit, along with a strop block, I've consistently achieved mirror-polished, hair-popping edges that surpass any factory edge. Having sharpened over a dozen blades, from Japanese chef's knives to Benchmade folders, I've made a surprising discovery that challenges my previous understanding of what a burr is supposed to feel like.

Despite reading numerous articles and watching videos, the common descriptions of a burr don't match my experience. Many sources describe a burr as a large, floppy piece of metal at the apex of the blade that you can feel hanging off like a "J" hook. They suggest detecting it by rubbing your thumb up from either side until it hooks over on one side.

However, in my experience, a burr is not an obvious, floppy piece of metal. Instead, it has a distinct tactile feel that I can only detect by lightly rubbing my finger perpendicular to the edge, feeling the texture of the edge itself. To me, a burr feels like an extremely sharp, serrated edge with many serrations, similar to broken glass. It's not usually flopped to one side but rather sticks straight out, so the "hook on thumb" method has never worked for me. Additionally, I've never been able to visually see the burr. Therefore, the commonly described jagged, J-shaped hook that you can see and feel with your thumb is not how I would describe a burr to someone.

I'm trying to clarify this because I'm teaching a friend how to sharpen knives on stones, and I want to ensure I'm providing accurate information.
So my description would NOT be a rough piece of J channel flopped over, but rather very sharp serrated glass tactile feel.

 

[Guy McVer]

It can vary a bit depending on the steel, but in general the big floppy burr is what you get from being a little too overzealous and sharpening a little bit more than you needed to. I mean, in general that's what a burr is... you've gone past the point of reaching the apex and you ended up sharpening a bit too much, so it forms a burr. But the big floppy burr is basically from the next level of overkill beyond that. If you sharpen just the right amount, then you won't really get a burr at all... at least not one that you can see or feel. It will be so small that you would need a microscope to see it.

Lots of people get lazy and don't maintain their knives regularly, or even abuse them to the point that their edges get really messed up, and so what they would consider sharpening is actually reprofiling. Hence how they end up with the floppy burrs. And then there are some people who just go ham on it to the point that they end up with the big floppy burr. In all fairness, it is faster to sharpen that way, even if you are taking off a little more steel than you need to.

The obsession with burrs is not justified in my opinion. If you sharpen your knife properly, and if you maintain it regularly, and you treat it well so that you don't need top reprofile it, then burrs aren't something you need to worry about too much beyond the act of stropping. To put it another way, if every single time you sharpen your knife your goal is to form a burr that you can feel, then is something is wrong. If you're trying to get a big floppy burr, then something is double wrong.

 

[TheOne45]

If you haven't seen it yet this article with high magnified photos might give you some hints:
Find 'scienceofsharp' site and there is an article: Seven Misconceptions About Knife Burrs

Other articles on this site also have lots of SEM photos of all kinds of burrs and clean edges after stropping or micro beveling.

After upgrading my sharpening stones to a complete range of Shaptons, from 320 to 5000 grit, along with a strop block, I've consistently achieved mirror-polished, hair-popping edges that surpass any factory edge.

How do you check if this is a true clean edge or there is a microscopic extension of the edge in a form of a burr which acts as hair-popping edge?

 

[Obsessed with Edges]

The 'feel' of a burr can vary widely, depending on how big it is, how thick it is and how strong it is.

A very thick burr can give that feeling of a jagged, serrated-like edge. Especially so if you cut yourself on it - they're vicious. These are the sort of burrs I notice most often on factory edges produced by very coarse belts on powered grinders, for example.

But other burrs that are very thin and formed from relatively soft, ductile steels can behave much more like very thin foil (called a 'foil edge'). They're the 'floppy' ones that can move around back & forth all day until they're sufficiently cleaned up & removed. You might not necessarily feel it with your fingertip either, as they're so light & flimsy. But you're more likely to notice how the cutting performance of the edge will vary widely from one cut to the next in something like thin paper, as the burr moves around.

And in spite of their reputation as being weakened portions of steel along the edge, sometimes burrs can be quite strong themselves in steels that retain ductility at relatively high hardness. I've noticed very strong burrs on steels like ATS-34 at HRC 60+ for example. Burrs like these simply won't be broken off unless or until they're adequately thinned and/or abraded away using ever-decreasing pressure during refinement honing. And because of their strength, these burrs can be aligned straight and will perform relatively well in cutting for some time.

 

[115Italian]

I think it’s more important to learn what a tiny almost invisible bur feels like. That large ones are obvious. Those small ones are what can give you the false sense of sharpness. Then suddenly you’re edge is gone quickly in use.

I think you’re right on the money. Aim to produce a small bur. Learn how to detect it and eliminate it through the sharpening process.