Burnt Edges

[Richard338]

Here's Larrin's article explaining the effect. We are talking about a tiny volume of steel at the apex, not grossly burning the steel with visible colors. I put on my entire final bevel by hand with diamond stones partly to avoid this.
FYI The standard protocol for tempering 3V is around 1000F. The Delta protocol is a "low temperature tweak" done somewhere around 400F. As explained in the article, apex temperatures under powered sharpening can exceed 1400F.

Does Sharpening with a Grinder Ruin Your Edge? - Knife Steel Nerds

You have to sharpen a new knife a few times to get it cutting well. Right? Or do you? Are knife manufacturers improperly sharpening their knives?

knifesteelnerds.com

 

[David Mary]

The Delta protocol is a "low temperature tweak"

I misspoke, and have correct "high" to "low" in my post.

The article does not define "belt sharpened". , i.e. at what grit, and whether platen backed belts or slack belts. I'd love to hear Larrin 's comments.

I slack belt sharpen with quick passes only up to 220 grit on flexible ceramic belts (they get honed/microbeveled by hand afterwards too), and I find my edges perform as they should.

I would be surprised if I learned I was leaving significant performance on the table, given how many comments I receive on my knives' longevity of cutting performance.

 

[Delgadonine]

You didn't define "routine sharpening".

Burning something means you transferred too much heat into it, as implicitly stated. So the answer is easy to determine based on what you define as routine sharpening.

Ok, I moving on.

 

[Richard338]

Magnacut has a low tempering temperature if you are targeting high hardness so it should be one of the easier ones to screw up. I have seen reports of some sub par factory edges. On the other hand I've convexed it to zero and not noticed any issue. Of course we don't know everything that goes on in the factory, only our own garage.

 

[Murdamook.3]

I’ve always been pretty agnostic toward this concept. I think it’s just kind of frightening sparrows. You’re going to use the knife, dull it, and sharpen it. Why worry if the edge is burnt? It was always weird to me that people got a knife and immediately took off the burnt material. I get they want the steel performance as fast as possible, but it’s lessening the life of the knife by doing so. Use the burnt edge until you have to sharpen it, if it is indeed burnt.

 

[oldmanwilly]

I have had a couple factory knives that had a bit of a burnt edge, specifically a Benchmade Griptillion. That knife in particular felt nicely sharp as I received it but that edge was very quickly filled and once sharpened again it held the edge for quite a bit longer. The issue I had was after two sharpenings it still never held the edge I was expecting from that steel so I sold it. I will never know if that knife had a deeply bad edge or an overall poor heat treat. I definitely soured my opinion of Benchmade.

I had the same issue with Benchmade's S30v, although I do not think it was part of the burned edge phenomenon. Rather, I sharpened my Volli at least a dozen times (reprofiling and everything) and, for the life of me, it would not hold an edge beyond the first few cuts into any material. I never had thiss issue with my S30V Spyderco knives owned and used around the same time. Benchmade just botched the heat treat on my blade. Later, they were proven to be intentionally tempering certain of their steels at a lower than recommended HRC. Completely turned me off of Benchmade, especially once they dropped 154CM and switched to S30V for their baseline steel. Bummer, because Benchmade was my first favorite brand for good quality knives.

As for the topic of this thread, I have often noticed better performance in several of my blades after a couple of good sharpening sessions. Thus I believe in the phenomenon.

 

[kobold]

Depends. At Spyderco they use coolants, so it is supposed to be under control. Smaller shops might use the dip method. It wont happen when hand sharpening.

 

[The Mastiff]

I've taken the position that most folks will be better off readjusting their geometry when having issues instead of chasing after "good " steel. Whatever works for them though. There are vastly different skill and knowledge levels involved with members here also which further muddies the issue. IMO, it's not a big problem at least with the knives I have been buying over the years.