Edge Angle vs Knife Steel - level on comparable edge strength by adjusting edge angle - to determine edge retention

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mobile1mobile1

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May 23, 2022
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I have maybe a bit a stupid question here.

So Knife Steels are measured in 3 dimensions
Corrosion Resistance
Edge Retention
Toughness

Now from Larry's book I learnt that edge angle has an over 50 times higher impact on edge retention than any other factor.

Now looking at online resources it seems that the lower the carbide content in a knife steel the slimmer the edge angle can be.

So practically speaking shouldnt we compare edge retention of knife steels using different edge angles - at a similar "toughness" levels. Meaning if I take a CPM-3V with 0.8% carbides I can probably run a much smaller angle than with a CPM-S9V with 2.3% carbides. So from a practical point of view what is the most narrow edge angle I can chose with CPM-3V to get similar edge strength/toughness as with CPM-S9V, and what is the resulting edge retention of those two steels with toughness standardized. My guess would be that a CPM-3V with a bit more narrow angle should by far outperform the S9V on edge retention.

3V has a much lower edge retention when using same edge angle than S90V. But adjusting the edge angle I think this might change, no:

I think in the chase for maximum edge retention going for a more narrow angle with tougher steels shouldnt that be more beneficial?

Or am I getting something wrong in this train of thoughts?
 
mobile1mobile1 said:
I have maybe a bit a stupid question here.

So Knife Steels are measured in 3 dimensions
Corrosion Resistance
Edge Retention
Toughness

Now from Larry's book I learnt that edge angle has an over 50 times higher impact on edge retention than any other factor.

Now looking at online resources it seems that the lower the carbide content in a knife steel the slimmer the edge angle can be.

So practically speaking shouldnt we compare edge retention of knife steels using different edge angles - at a similar "toughness" levels. Meaning if I take a CPM-3V with 0.8% carbides I can probably run a much smaller angle than with a CPM-S9V with 2.3% carbides. So from a practical point of view what is the most narrow edge angle I can chose with CPM-3V to get similar edge strength/toughness as with CPM-S9V, and what is the resulting edge retention of those two steels with toughness standardized. My guess would be that a CPM-3V with a bit more narrow angle should by far outperform the S9V on edge retention.

3V has a much lower edge retention when using same edge angle than S90V. But adjusting the edge angle I think this might change, no:

I think in the chase for maximum edge retention going for a more narrow angle with tougher steels shouldnt that be more beneficial?

Or am I getting something wrong in this train of thoughts?
Click to expand...

Hardness ( Rockwell ) HRC ..
Toughness
Edge retention
Corrosion Resistance
& I suppose ease of sharpening ..

Now in regards to edge retention :
Toughness
Hardness
Bevel angle
& What I have touched on recently is GRIT !
I was doing some preliminary DUAL GRIT testing , and then got side tracked into Coarse grit testing ..

I would dare to say that most steels have a sweet spot for :
Bevel angle
& Grit ..
Get these right and you can really push edge retention ...

I would also say that most people don't care enough to experiment & are quite happy just making a knife sharp , never mind - stays sharp !
Speaking for myself , I'm not that fond of constantly having to sharpen a knife ! So Stays Sharp is kind of a pet project !

Just depends on what your priorities are ?

Also ? Where are you getting this information from ?
There are a insane amount of variables to take into account .
Remember , all these so called knife facts have to be taken with a barrow full of salt Cos of the variables ! ( nasty / nasty / variables )

Facts of life :
F1 - Steels aren't steels
F2 - It's how well the steel was cooked
F3 - Any steel can be bad
F4 - Any steel can be good ( Variable being - how well it was cooked )
F5 - If you can't sharpen a knife properly (?) how good is it going to be ?

Oh those nasty variables ! The most important thing to remember is - the variables !

Sharpening !
A) Learn to remove the bur
B) Find the bevel angle the steel will support
C) Find the grit that gives the best edge retention

Get these right , & you can live long and prosper !
 
This is probably not something that you need to think about too much. If you're dealing with a knife that you bought, then the manufacturer probably already set it at the angle you want to use, so just match that and call it good. Why bother going to the trouble of re-profiling it? Sharpen it when it gets dull. In fact, ideally just sharpen it after every time you use it. This is often considered the best practice, and when you do that it doesn't really matter how good the edge retention is anyway. It will never have the chance to be a factor.
 
Guy McVer said:
This is probably not something that you need to think about too much. If you're dealing with a knife that you bought, then the manufacturer probably already set it at the angle you want to use, so just match that and call it good. Why bother going to the trouble of re-profiling it? Sharpen it when it gets dull. In fact, ideally just sharpen it after every time you use it. This is often considered the best practice, and when you do that it doesn't really matter how good the edge retention is anyway. It will never have the chance to be a factor.
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Well different use cases.. knife mfg's they tune their knifes to the average customer use case.
In my case knife I use down to cut down amazon boxes I go with a 10 degree angle - 5 on each side - and it literally cuts forever and it's super sharp. For knives with a rougher use profile - I go with higher angles. So I just refuse the one size fits all thing and second I like not having to sharpen them all the time.
 
mobile1mobile1 said:
I like not having to sharpen them all the time.
Click to expand...

Well here's the trade-off: you can stay on top of your edge and not really ever spend much time sharpening it when you do, or you can let your edge go unmaintained and then have to spend a lot more time on it later. It's totally your call, but it seems obvious to me that in the end you're just making more work for yourself by re-profiling the knife in the first place and then waiting until it goes dull before you actually do anything to fix it.
 
Factory.jpg


Hmmm ....

Guy McVer said:
Well here's the trade-off: you can stay on top of your edge and not really ever spend much time sharpening it when you do, or you can let your edge go unmaintained and then have to spend a lot more time on it later. It's totally your call, but it seems obvious to me that in the end you're just making more work for yourself by re-profiling the knife in the first place and then waiting until it goes dull before you actually do anything to fix it.
Click to expand...

???????????????? ................ Hu ?

So ? You take a little effort to give yourself the best edge you can .. And some how that = more work ..
How does a longer lasting edge = more work ?
Over the life of the knife or user , it should = less work ! & a longer lasting knife !

How much time does the actual person take to maintain an edge ?

Edge maintenance = How long ?
For me it's a few minutes .. Like maybe 10 minutes tops if the knife is dull or the edge damaged ..
Re profiling takes longer , but that's part of the process of discovering the edge that will perform the best ..
No different to people Tuning their Car , or Motor Bike ... Or getting your Fav Lounge chair just right !
Once your there , it's easy sailing ..

Obviously some people don't care ! That's a given ...
Another given is that some people do care ..
How would people feel about Doctors or Nurses that didn't care ?
& If you don't care ? Why even bother posting ?
As for factory edges ? Some factories / manufacturers might care and some might not !
It's up to the user to decide if they are happy with Ho Hum . or want to chase the cherry on top !
And chasing the cherry , they might learn something (?) . ( Maybe / hopefully )
 
mobile1mobile1 said:
...Now looking at online resources it seems that the lower the carbide content in a knife steel the slimmer the edge angle can be....
Click to expand...
The carbide content has almost nothing to do with how slim an angle you can use on a knife.

The greater the carbide volume the less tough it generally is, but toughness doesn't determine how thin a knife can be. You can have a super tough basic steel like 420HC that is in the mid to high 50's HRC and it will not work well at very thin geometry compared to something like M4 in the mid 60's HRC which will hold up fine with that same geometry. There are steels that have less toughness but high edge strength that will outperform other tougher steels with less edge stability.

Edge retention will be different depending on what you are cutting as well. Things like corrosion resistance will play a large part in some cases for example.
 
old4570 said:
Factory.jpg
Click to expand...
I get mine at the dollar store. They're cheap and worth every penny. You can get a lot of use out of one of these. I've used them a lot for ton of different things, but funnily enough I'm pretty sure that I haven't opened a single box with one of them yet. 😄
 
Guy McVer said:
Well here's the trade-off: you can stay on top of your edge and not really ever spend much time sharpening it when you do, or you can let your edge go unmaintained and then have to spend a lot more time on it later. It's totally your call, but it seems obvious to me that in the end you're just making more work for yourself by re-profiling the knife in the first place and then waiting until it goes dull before you actually do anything to fix it.
Click to expand...

A thin, sharp high performing knife will stay sharp longer, because it takes less force to push the knife through the work.


Busse gave me a knife with a .065" bte. ....because they care more about warranty than they do about knives cutting.

Valid Topic.
 
Crag the Brewer said:
A thin, sharp high performing knife will stay sharp longer, because it takes less force to push the knife through the work.
Click to expand...

Yes, yes. If the steel is strong and the heat treat is good, then a thin edge can even last longer because it will still be thin even as it gets worn down. A knife is a wedge, and a thin wedge is still effective even if it's not perfectly apexed. This is not in doubt. However, it makes no real difference if you are in the habit of keeping your edge maintained as you use it rather than waiting for it to lose effectiveness before you ever bother to touch it up.

I can't help but think that the people who are so obsessed with having a longer lasting edge are the same type who either won't or can't actually sharpen a knife in the first place. These are the same kind of people who rely on fancy equipment designed specifically to remove any need for thought or skill. These guys are completely helpless without that equipment and have no clue how to actually sharpen a knife freehand. I think that they are cheating themselves and making excuses for it, and manufacturers are obviously going to be more than happy to cater to this as long as they can profit from it.

edit: to be absolutely clear, the reason why I think this is such a bad thing is that aside from people not actually learning how to sharpen a knife, it's also that the kind of knife which can handle such a thin edge tends to be more expensive on average.
 
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The proof of the pudding , is how good it tastes ... Not how it was made !
I have made the challenge before ...

Put your edge where your sharpening is ....
 
I agree with the premise the OP states, which is basically that toughness can be tweaked to it's particular advantage via geometry (to a certain point). It is why I have enjoyed M4 so much over the years. "Chippier" steels have me less acute in secondary bevel.
 
Officer's Match said:
I agree with the premise the OP states, which is basically that toughness can be tweaked to it's particular advantage via geometry (to a certain point). It is why I have enjoyed M4 so much over the years. "Chippier" steels have me less acute in secondary bevel.
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That's kinda where I fall too. I tend to like the tougher steels. IF you know it's not going to be a hard use knife you have the option to thin it out, and it will basically preform like a steel with higher edge retention. Decide you need a more stable edge for harder work, you can put a quick secondary bevel on.
 
chalby said:
The carbide content has almost nothing to do with how slim an angle you can use on a knife.

The greater the carbide volume the less tough it generally is, but toughness doesn't determine how thin a knife can be. You can have a super tough basic steel like 420HC that is in the mid to high 50's HRC and it will not work well at very thin geometry compared to something like M4 in the mid 60's HRC which will hold up fine with that same geometry. There are steels that have less toughness but high edge strength that will outperform other tougher steels with less edge stability.

Edge retention will be different depending on what you are cutting as well. Things like corrosion resistance will play a large part in some cases for example.
Click to expand...

According to this: https://knifesteelnerds.com/2018/08/27/what-is-edge-stability/
Edge Stability has a few components: Edge Rolling - Higher hardness means higher yield stress.
Looking at various properties of steel there seems to be a clear correlation of carbide content vs toughness. The less carbide the tougher the steel.

According to Larry, one needs low carbide volume and small size of carbides.

The ultimate test would be, take the highest edge stability steel and one should get edge retention that should blow everything else out of the water - just by using a smaller angle - since the angle is the by far biggest component as far as edge retention goes. I would think a CPM-3V should have one of the highest edge stability out there.
 
So the ultimate question to me is, which steel has the highest edge stability? and then correlation to edge retention - maybe one would see that edge retention is best done by maximizing edge stability and lower angles.
 
mobile1mobile1 said:
According to this: https://knifesteelnerds.com/2018/08/27/what-is-edge-stability/
Edge Stability has a few components: Edge Rolling - Higher hardness means higher yield stress.
Looking at various properties of steel there seems to be a clear correlation of carbide content vs toughness. The less carbide the tougher the steel.

According to Larry, one needs low carbide volume and small size of carbides.

The ultimate test would be, take the highest edge stability steel and one should get edge retention that should blow everything else out of the water - just by using a smaller angle - since the angle is the by far biggest component as far as edge retention goes. I would think a CPM-3V should have one of the highest edge stability out there.
Click to expand...
Either you are on very friendly terms with Larrin or misread his name lol. I thought it was stupid auto-correct in your first post.

Anyway, yes toughness does have a lot to do with edge stability; I probably explained that poorly. The point I was making was that just because a steel is tough doesn't mean it won't roll easily with a fine edge angle; there are other factors. Check out BBB's youtube channel where he puts steels like 15V and others through some pretty tough tests. 15V hasn't got good toughness numbers but survives some pretty hard use(abuse?). And as I said it also depends on what you are cutting. If you are just slicing soft materials you can probably afford to use a very acute angle and even a fairly low toughness/edge stability steel as well. If you don't know exactly what you will be cutting on a given day, then most people use an edge angle that is somewhat utilitarian/middle ground.

There are too many variables to really come to a definitive answer. I think a lot of us on this forum like to experiment with different edge angles, I know I usually end up reprofiling most of my knives to thinner than the factory edge for the added edge retention. At the end of the day I think that the advantages of the wear resistance of high carbide steels will mostly beat tougher steels with good edge stability. I suspect that for most applications the difference in the edge angle that is possible for a certain job between the two isn't going to be huge. That's just my feeling anyway.

Why don't we ask an expert for his opinion? Larrin Larrin or is it Larry?
 
Larrin said:
The more acute the angle the higher the strength/hardness and toughness you need. I don’t go by Larry and never have. The name Larrin doesn’t necessitate a nickname.
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So, based on your charts, I would assume that Magnacut and Cruwear would be the optimal steels for acute angles because they can achieve high hardness while retaining better toughness than other steels that can achieve 64+ hrc?
 
Blade Lab said:
So, based on your charts, I would assume that Magnacut and Cruwear would be the optimal steels for acute angles because they can achieve high hardness while retaining better toughness than other steels that can achieve 64+ hrc?
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There might be something with even less carbide that could do somewhat better, though it isn't always clear how much toughness is "enough" as opposed to hardness being the main requirement. And of course less carbide means less wear resistance so in some ways those steels may be less "balanced." There may be interesting research opportunities there but it becomes very complicated and specific when you try to optimize any certain scenario. Which is partly why I prefer measuring the specific properties, ie toughness, hardness, wear resistance while slicing, corrosion resistance, etc. and then more optimal solutions can be selected for different applications. It is then up to makers/users to optimize their knives and edge angles.
 
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