Edge rolling

R

RugerNurse

Joined
Jul 13, 2019
Messages
640
Hi all, the edge of my Spyderco salt in Lc200n rolling very easily. Like when I’m cutting something on a plate. I can’t figure out what I’m doing wrong. I try to make sure it is deburred after sharpening. The angle is set to 17°
 
Spyderco runs their LC200N at 56-58HRC, which is normal for the steel but definitely on the softer end of things. Ceramic plates will destroy it. I've had pretty good luck using Rex 45 and ASP-60 to cut steak on ceramic plates without the instant dulling you get with stuff like LC200N, S30V, etc.
 
Thanks all. I guess I’m still confused between hardness and toughness. Would a harder knife hold up better against something like cutting on ceramic or would it need to be tougher?
 
RugerNurse said:
Thanks all. I guess I’m still confused between hardness and toughness. Would a harder knife hold up better against something like cutting on ceramic or would it need to be tougher?
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Toughness is resistance to chipping, breaking and cracking.

Strength -- a proxy usually for hardness -- is resistance to rolling, denting and bending.

I'd suspect a burr.
 
Sidebar to the question, but awhile back my wife bought some compressed bamboo plates to take camping. They have a similar feel to melanine but don’t seem quite as hard.

I recently started using them instead of regular plates for steaks, etc., to keep my edges sharper and they’ve worked well for this purpose…
 
RugerNurse said:
Thanks all. I guess I’m still confused between hardness and toughness. Would a harder knife hold up better against something like cutting on ceramic or would it need to be tougher?
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Go for harder rather than tougher steels if you will cut a lot on ceramic plates.
 
kobold said:
Go for harder rather than tougher steels if you will cut a lot on ceramic plates.
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I don’t need to cut on the plates, it was something I just noticed but forgot that ceramic is harder. I thought it was a problem with my sharpening.

In general a tougher steel would resist rolling right? I thought H1 and LC200N were supposed to be tough.
 
You sharpen knives on ceramic. Like the Spyderco sharpener…

Trying to cut on ceramic will have the opposite result..as you have found.
 
RugerNurse said:
I don’t need to cut on the plates, it was something I just noticed but forgot that ceramic is harder. I thought it was a problem with my sharpening.

In general a tougher steel would resist rolling right? I thought H1 and LC200N were supposed to be tough.
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No, rolling and deformation comes from a lack of strength/hardness.
 
RugerNurse said:
Next dumb question: so the higher the Rockwell the harder is it, does that make the strength go up too?
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A higher Rockwell knife will be more likely to suffer from chipping whereas the same steel at a lower Rockwell hardness will deform easier, but is more likely to roll rather than chip. This isn’t always the case but is true way more often than not.

A roll is much easier to fix through honing and stropping than a chip, which needs to be sharpened out to be repaired. The reason people are saying to get a higher hardness knife is that it’s less likely to deform and lose its edge if it hits a hard surface like glass, stone or ceramic in this case. However if it does deform, it will most likely chip rather than simply roll and will be a bigger pain to fix. It’s all a balancing act between edge retention and toughness. A “stronger” edge (one with better edge retention) might in theory hold an edge longer before going dull but is also more likely to chip than a tougher edge, which in turn might not stay sharp for as long.

It can be quite confusing especially with all the different nomenclature people are using to refer to the same characteristics but in short a harder edge is less likely to roll and go dull but is more likely to chip. A softer edge is more likely to roll and will dull faster but less likely to chip. In general, if you want to keep a knife sharp, avoid letting the cutting edge touch anything ceramic, stone, glass, bone, or anything else harder/nearly as hard as the blade steel.
 
kafolarbear said:
A higher Rockwell knife will be more likely to suffer from chipping whereas the same steel at a lower Rockwell hardness will deform easier, but is more likely to roll rather than chip. This isn’t always the case but is true way more often than not.

A roll is much easier to fix through honing and stropping than a chip, which needs to be sharpened out to be repaired. The reason people are saying to get a higher hardness knife is that it’s less likely to deform and lose its edge if it hits a hard surface like glass, stone or ceramic in this case. However if it does deform, it will most likely chip rather than simply roll and will be a bigger pain to fix. It’s all a balancing act between edge retention and toughness. A “stronger” edge (one with better edge retention) might in theory hold an edge longer before going dull but is also more likely to chip than a tougher edge, which in turn might not stay sharp for as long.

It can be quite confusing especially with all the different nomenclature people are using to refer to the same characteristics but in short a harder edge is less likely to roll and go dull but is more likely to chip. A softer edge is more likely to roll and will dull faster but less likely to chip. In general, if you want to keep a knife sharp, avoid letting the cutting edge touch anything ceramic, stone, glass, bone, or anything else harder/nearly as hard as the blade steel.
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Thanks for the explanation. I value LC200N’s ability to resist rust because I use it all the time to cut food for kids and can wash it off. I’ll thought the toughness I heard about meant it would roll. I won’t use plates any more haha.
 
RugerNurse said:
I don’t need to cut on the plates, it was something I just noticed but forgot that ceramic is harder. I thought it was a problem with my sharpening.

In general a tougher steel would resist rolling right? I thought H1 and LC200N were supposed to be tough.
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No, a harder steel will increasingly resist rolling. But the tradeoff is some loss of toughness. While the edge may not roll as easily, it could chip or crack easier. Tradeoffs. To add more confusion, it is conceivable to increase toughness at every level of hardness, and vice versa. But the tradeoff will persist. We live in a multivariate world.
 
RugerNurse said:
Thanks for the explanation. I value LC200N’s ability to resist rust because I use it all the time to cut food for kids and can wash it off. I’ll thought the toughness I heard about meant it would roll. I won’t use plates any more haha.
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LC200N from what I hear is a fine steel, but yeah in general for food prep use a wood or plastic cutting board, even a paper plate is a good option. If you are cutting on something like a ceramic plate, try to avoid cutting all the way through the food and hitting the edge on the plate, try to cut maybe 90% of the way through and just kind of tear apart the last bit using a fork. I'm yet to find the steel that won't get messed up really quickly cutting on ceramic, so don't sweat your steel choice too much. If you're still confused with any of the concepts or terminologies, please feel free to keep asking. Knife and steel performance is a topic that can be as simple or complicated as you'd like to make it, and while Larrin Larrin is definitely the subject matter expert, I feel I can also explain these things reasonably well if need be.
 
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