Pros and cons of taking high end steels to low RC.

J

Jamesh Bond

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Jan 14, 2007
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This question popped to mind, and searches werent too specific.

Examples would be Chris Reeve and Emerson.

They both use good steel, CR more so, but take it to a very low hardness compared to what could be attained. Im actually quite fine with this, as i like my blades to be a little tougher, even if im gonna be sharpening more. With most makers following the trend of taking all these super steels to the brittle range, im actually missing out on knives id otherwise want. My preference.

Anyway. So the first reason would obviously be toughness.

So what is the performance increase of using super steels over simple steels when the target RC hardness is planned to be low ?

I would assume the high carbide content would be another obvious advantage, as well as corrosion resistance.

Am i somewhat on the right track here ? I suspect i am, but could those who are knowledgable educate me ?

Thx.
 
Many modern stainless steels maintain high toughness with a pretty high rc. Elmax for example.

My question is, what tasks do you do with your folders that requires uber toughness?

I have a zt 0620cf that I have thrown, used to pry, scrape and yes even the dreaded batonning... not something I do every day but I was camping and did it just for the hell of it. M390 has never failed in anyway.. that's why I ask what tasks do your folders see?


My opinion is you have a phobia of steels being brittle, in actual use I have yet to snap a folder blade. I say venture out your comfort zone and try a great steel and use it like you would normally, it will probably surprise you.
Jamesh Bond said:
This question popped to mind, and searches werent too specific.

Examples would be Chris Reeve and Emerson.

They both use good steel, CR more so, but take it to a very low hardness compared to what could be attained. Im actually quite fine with this, as i like my blades to be a little tougher, even if im gonna be sharpening more. With most makers following the trend of taking all these super steels to the brittle range, im actually missing out on knives id otherwise want. My preference.

Anyway. So the first reason would obviously be toughness.

So what is the performance increase of using super steels over simple steels when the target RC hardness is planned to be low ?

I would assume the high carbide content would be another obvious advantage, as well as corrosion resistance.

Am i somewhat on the right track here ? I suspect i am, but could those who are knowledgable educate me ?

Thx.
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shinyedges said:
Many modern stainless steels maintain high toughness with a pretty high rc. Elmax for example.

My question is, what tasks do you do with your folders that requires uber toughness?

I have a zt 0620cf that I have thrown, used to pry, scrape and yes even the dreaded batonning... not something I do every day but I was camping and did it just for the hell of it. M390 has never failed in anyway.. that's why I ask what tasks do your folders see?


My opinion is you have a phobia of steels being brittle, in actual use I have yet to snap a folder blade. I say venture out your comfort zone and try a great steel and use it like you would normally, it will probably surprise you.
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Toughness has a direct correlation to edge stability. A steel that is tough will roll, rather than chip. Personally, I'd rather my edges roll instead of chip, ymmv.

Every steel is different though, and some steels can attain a high hardness while still remaining tough. Rocksteads YXR7 for example, can easily reach 65hrc and still exhibit a high level of toughness. Their ZDP-189 at 67hrc isn't very tough, however. This is why they offer 2 choices of steel for users that have different cutting tasks.
 
The initial post appears to be coming from a position that lower hardness = higher toughness. This is a misconception that pervades knife making. Dropping the hardess a few points by raising the tempering temperature a little can produce lower toughness pretty commonly. It is highly steel specific and process specific.

Lowering the hardness on highly alloyed steels will lower the strength, but much of the wear resistance will be maintained, as that is primarily related to carbides and their volume. As dulling of edges is often related to deformation, it might lead to a loss of edge retention. It depends on what the knife is used for and how.
 
While toughness is generally correlated with edge stability so is hardness, and steels now a days that maintain high toughness WITH higher hardness also have exceptional edge stability even in thinner grinds, the custom makers on this forum show this very well.

Like 3v taking to 60+ hardness being pounded with a hammer through nails, concrete , and cinder blocks. Nathan the machinist has even video taped it. Not a whole lot of chipping going on in his videos.

Like me2 said , lower rc doesn't always mean a tougher blade, and also as he said it is highly steel specific. Not all steels need to be low rc to be tough, I prefer high edge stability and high toughness.
Blues Bender said:
Toughness has a direct correlation to edge stability. A steel that is tough will roll, rather than chip. Personally, I'd rather my edges roll instead of chip, ymmv.

Every steel is different though, and some steels can attain a high hardness while still remaining tough. Rocksteads YXR7 for example, can easily reach 65hrc and still exhibit a high level of toughness. Their ZDP-189 at 67hrc isn't very tough, however. This is why they offer 2 choices of steel for users that have different cutting tasks.
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Knife makers cannot please everyone, no matter what they do. Lots of people here hate "super steels" or locks or no locks or pocket clips or no pocket clips.

I think the theory behind the relatively lower Rc of the Sebenza is that it makes the knife easier to sharpen. Diamond stones minimize that argument, but lots of people dislike diamond stones.

The bottom line: If you know what you need in a knife, there is likely to be an abundance knives that will fit your needs in today's market.
 
me2 said:
The initial post appears to be coming from a position that lower hardness = higher toughness. This is a misconception that pervades knife making. Dropping the hardess a few points by raising the tempering temperature a little can produce lower toughness pretty commonly. It is highly steel specific and process specific.

Lowering the hardness on highly alloyed steels will lower the strength, but much of the wear resistance will be maintained, as that is primarily related to carbides and their volume. As dulling of edges is often related to deformation, it might lead to a loss of edge retention. It depends on what the knife is used for and how.
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Excellent. Thx for that answer.
 
OP, what do you consider lower toughness? 56? 58?

What me2 said is true. I have noticed that most steels have a preferred Rc range. Going beyond it in either direction often does not improve and sometimes hurts the properties of the steel.
 
Twindog said:
Diamond stones minimize that argument, but lots of people dislike diamond stones.
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Why would 'a lot of people' dislike diamond stones?

Not disputing, just asking.

Me, Im a fan - especially since its a breeze to sharpen my Beta titanium knives on diamond stones.
 
After more than a few years in this hobby I see an interesting trend; many knife companies offering their knives at a less than optimal hardness...

For example: Busse, a semi-custom knife company has dropped the hardness on their knives. Sources I've seen quote 2 HRC point drops in hardness compared to models offered in past which represents a noticeable drop in edge retention. Spyderco's first run Gayle Bradleys were released at a higher HRC than the second generation models; that's why I bought both versions. :rolleyes:;):thumbup:

Since many buyers of the brands being discussed here are discerning knife collectors ;), I see no reason for the manufacturers to "dumb down" (for lack of a better term in my vocabulary) the blade steel being offered; especially in a folding knife.

Even simple carbon steel fixed blades are often released at too low HRC in my opinion; why would you want to carry a something that goes butter knife dull after a few cuts?...


I'll step down off my soap box now...:rolleyes:;):D
 
BladeScout said:
Why would 'a lot of people' dislike diamond stones?

Not disputing, just asking.

Me, Im a fan - especially since its a breeze to sharpen my Beta titanium knives on diamond stones.
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Like so many things, it's more about personal preference. The Edge Pro vs Wicked Edge argument often comes down to waterstones vs diamond stones. I like diamond stones better, but they wear out for me much faster than others, although they don't need to be flattened. Some like the edges they get off waterstones or SiC better. Some can't get rid of the deep scratches from coarse diamonds.

Mostly, people just come up with their own favorite thing/method/brand/religion/whatever and aggressively defend it from people with different thinking.
 
I use my 10 Inch DuoSharp Bench Stone for all of my casual sharpening. I have an Edge Pro Apex and Spydie SM, but seldom feel the need to use them, although they work very well.
For my kitchen knives and my Brad Southard AVO, a few swipes on the "fine" side of the stone, followed by a tiny amt of stropping, keeps me very happy.
 
Running a lower HRc is one thing but I have noticed there is a hugh lack in heat treat and tempering quality.

I've said it before and I will again here, S30V is one of the most inconsistent steels I sharpen on the regular. It's different from knife to knife from the same maker let alone different makers, with very few getting it right. IMO, it's not a hardness issue but an issue with the whole process. ESSE 1095 is a good example of low hardness done right, you can feel it in the steel as you sharpen and by how well the edge finishes from the stone.
 
Exactly.

Soooo . . .

Per the question, what gains ( or losses ) happen when using the higher alloy steels at low hardness . . . ?

Thx.
 
Jamesh Bond said:
Soooo . . .

Per the question, what gains ( or losses ) happen when using the higher alloy steels at low hardness . . . ?
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(You end up with large burrs, rolled edges, and easy to dull blades). That's been my experience with cpm m4.
 
From my point of view any steel that is not as hard as it can be without chipping is not interesting to me. How hard that is depends on the steel, the edge geometry, the heat treatment (microcracks...), and the intended use.

That said the only knife I have ever had chip out on me was a high hardness plain carbon steel ground with a low angle zero edge.

The reason competition choppers are often made from high hardness CPM M4 is because it has phenomenally high fracture strength (over 700,000psi)...compare this to a mild low carbon steel with a yield strength of 40,000psi, or a common stainless steel in the 150,000psi range.... if a steel has a strength measured that high its going to be damn tough even with very fine sections.

There is little to no advantage to have it softer so the edge rolls over, instead of chipping, because both are an edge failure and means the knife is no longer sharp. I don't want a knife I have to "fix" the edge on all the time, I want one that does the job the most with the least effort.

For instance if you want tough, choose a "tough" steel and run it hard like 3v at 61+, its still very very tough compared traditional steels, and even though it has fairly low Vanadium carbides the extra hardness adds to its real world edge holding where many edges become dull due to deformation, not abrasion.
 
highestpoint said:
I haven't had this problem with my 810. It has great toughness and holds an edge without chipping or rolling. What angle do you sharpen it at?
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Yeah, haven't had that problem with my late model 810, or any of the 3 spydercos in m4.
I vary the angles from 25 to 35 inclusive, just for experiment.
At the acute angles there's rolling. At 35, just premature dulling mostly.
For the record, the mini's aren't quite as bad as the early 810.
 
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