Which Steel Has the Best Edge Retention?

[knarfeng]

This article reminds me of what cliff stamp (yeah I said it lol) has been saying he has been observing for years in his own testing, that edge geometry is more important to edge retention than the steel type itself - although it does play a roll obviously. Also he has recorded that lower edge angles have longer edge retention when cutting soft materials. Good to see a second validation of this

* updated w/ links (not conclusive research but interesting nonetheless)

• coarser edges seem to have longer edge retention when slicing soft materials
• edge retention increases as angle decreases

That's OK Buck validated it in the late 90's when they developed their Edge 2000 blade profile.

CJ Buck posted about it here on BF in 2001. Unfortunately the links to the data plots are kaput. But the text gives the gist of it. They found that profile was more important than alloy, but that if two blades had the same profile, the blade alloy then had an impact on the edge retention.
https://www.bladeforums.com/threads/catra-edge-testing-results.127499/

The geometry of edge has a substantial impact on the initial sharpness as well as the longevity of the edge. Optimum edge geometry on good cutlery steel will outperform a common edge geometry on premium steel.

 

[MolokaiRider]

I read through both articles a couple of times, thanks for posting.

I appreciate the time taken to put this information together and sharing (for free no less).

 

[Wowbagger]

You are allowed to disagree with my opinion.

Sure. That's what science is about. Challenge everything. Test it for yourself. See what happens.
That and I just love to argue and have a good time.

Thanks for doing all this research and compiling and hard work for us Larrin

 

[marchone]

That's OK Buck validated it in the late 90's when they developed their Edge 2000 blade profile.

CJ Buck posted about it here on BF in 2001. Unfortunately the links to the data plots are kaput. But the text gives the gist of it. They found that profile was more important than alloy, but that if two blades had the same profile, the blade alloy then had an impact on the edge retention.
https://www.bladeforums.com/threads/catra-edge-testing-results.127499/

This raises two questions to a user. What is a good blade geometry? And how can the consumer achieve it?

 

[Bob6794]

That's OK Buck validated it in the late 90's when they developed their Edge 2000 blade profile.

CJ Buck posted about it here on BF in 2001. Unfortunately the links to the data plots are kaput. But the text gives the gist of it. They found that profile was more important than alloy, but that if two blades had the same profile, the blade alloy then had an impact on the edge retention.
https://www.bladeforums.com/threads/catra-edge-testing-results.127499/

Had a big reply earlier in the day I think I just post the link instead. I found it interesting. It has a lot of info that is relevant to what you linked I believe. Catra testing and all backing this up. Also pointed out how little difference there was between 420hc and bg42 if your the type of person who tends to keep your knife sharp, but if you use it till it dulls than there is a bigger difference. Something I found to be true in real world use too with quite a few steels.

http://www.swordforum.com/forums/sh...ity-and-edge-retention-as-effected-by-profile

Edited in:
Actually I think this contains the graphs for what you linked.

 

[Wowbagger]

That’s a good question; I don’t know. We should ask CATRA.

Funny; I thought I saw that spelled out in one of your posts or links a couple months ago.

 

[Wowbagger]

This raises two questions to a user. What is a good blade geometry? And how can the consumer achieve it?

Time for my infamous post of Mr Carter.
This is THE STUFF !

How to achieve it ?

I'm not too sure what you are asking there. Whether you mean how to decide what is best for your steel and your use or how to change the geometry.

I reprofile on a DMT Extra Coarse 10 inch bench stone if that is what you mean. Using magic marker on the sharpening bevel and free handing until I get the approximate geometry I want (both for angle and thinness behind the edge) then I refine the edge on my Edge Pro Apex.

 

[knarfeng]

http://www.swordforum.com/forums/sh...ity-and-edge-retention-as-effected-by-profile

Actually I think this contains the graphs for what you linked.

Yes. I recognize them. The graphs in that 2006 Cliff Stamp post are the ones that CJ Buck originally posted here on BladeForums. Cliff Stamp apparently had the foresight to copy the graphs and store them offline. If you combine the graphs in Cliff Stamp's post with CJ Buck's post in the thread I cited, you get the entire original post that CJ Buck made on BF in 2001. (I think Cliff cited the same BF thread that I did, but with the forum software change a couple of years ago, the link is no longer valid.)

 

[Wowbagger]

By the way, how thick is a CATRA card?

Here we go :
Test Media
Specially formulated and quality controlled card with controlled Silica content of 5% supplied in: 10kg packs.......Thickness 0.31 mm >± 0.02 mm.....Weight 200g ± 10g/m²...Cut into Strips 10mm wide x 560 mm long . This is a complex test paper and is critical to the accuracy of the test system.

I found that here : Link> > > >

 

[miso2]

Here we go :
Test Media
Specially formulated and quality controlled card with controlled Silica content of 5% supplied in: 10kg packs.......Thickness 0.31 mm >± 0.02 mm.....Weight 200g ± 10g/m²...Cut into Strips 10mm wide x 560 mm long . This is a complex test paper and is critical to the accuracy of the test system.

I found that here : Link> > > >

Thanks.
But see post #34 and Larin's response in #35.

 

[Wowbagger]

But see post #34 and Larin's response in #35.

Double Doh
Looks like I missed some posts.

 

[DeadboxHero]

Make you wonder,why use highly wear resistant steels if you maintain your gear properly?
However, I have found the the edges with high Vanadium steels have a lot of Raw aggression at the same grit and sharpness. Cuts very ferociously, very enjoyable. Especially with a 300-600 grit edge and a bump on diamond/CBN strops

The heavy volume of very hard vanadium carbides seem to reinforce the teeth at the apex and the stropping seems to polish the teeth.
These types of steel with lower geometries are fantastic.
It's not that these steels can't be used with lower geometries, it's just they are more prone to damage with user error.
Also the extreme cost to manufacturers to grind the blades thinner and more complaints from improper use.

Had a big reply earlier in the day I think I just post the link instead. I found it interesting. It has a lot of info that is relevant to what you linked I believe. Catra testing and all backing this up. Also pointed out how little difference there was between 420hc and bg42 if your the type of person who tends to keep your knife sharp, but if you use it till it dulls than there is a bigger difference. Something I found to be true in real world use too with quite a few steels.

http://www.swordforum.com/forums/sh...ity-and-edge-retention-as-effected-by-profile

Edited in:
Actually I think this contains the graphs for what you linked.

 

[vish]

S90V kitchen knives are much better!!!

 

[Larrin]

• coarser edges seem to have longer edge retention when slicing soft materials

Phil Wilson also reports that a coarser edge leads to longer slicing edge retention. For some reason we didn't see the same behavior with the 154CM CATRA study I published before. However, I have reason to believe that isn't a universal result even for CATRA. I'm hoping we can conduct another small CATRA study to look at it again.

 

[Revolverrodger]

Could you tells us how much the increase in one hrc point affects the number of cuts (while correcting for other variables)

 

[Larrin]

Could you tells us how much the increase in one hrc point affects the number of cuts (while correcting for other variables)

From the article:
The coefficient for hardness of 15.8 means that the regression predicts an increase in ~16 mm TCC for each point of hardness (Rockwell C). If this holds true across all steel types (perhaps a big if) that would mean that low wear resistance steels would get more of an increase percentage-wise than a high wear resistance steel. In other words, an increase from 200 to 232 TCC with a 2 Rc increase is more significant than from 800 to 832. There were some cases due to test variability where there wasn’t much difference in TCC with hardness. Here are a couple examples with clear trends:

There aren’t enough significant hardness comparisons in the data to say much else definitively. I would imagine that the improvement in TCC with increase in hardness would be greater with low edge angles since there is a larger spread of values among steel types with low edge angles. But quantifying that is difficult with the current dataset. The increase of 15.8 mm per Rc is also within range of another independent study performed with CPM-M4 [5]. Ignoring one potential outlier, the increase with hardness was 12.8 mm per Rc.

The CATRA test uses a fixed load and has little lateral stress on the edges of the knives. In “normal” cutting by humans there are larger stresses on the edges which can lead to edge rolling or chipping, especially with thin and low angle edges. Those effects are largely not seen with CATRA and therefore this measured effect of hardness is largely due to an increase in wear resistance. In cutting by humans or in cutting of hard materials there may be a stronger effect of hardness due to other mechanisms like edge rolling.

 

[Revolverrodger]

16mm doesn’t seem like alot
I tend to recall ( maybe I’m wrong) that hrc is an exponential scale... I would have expected a larger effect

Did you account for interactions between variables in your linear model?

Very interesting analysis by the way

From the article:
The coefficient for hardness of 15.8 means that the regression predicts an increase in ~16 mm TCC for each point of hardness (Rockwell C). If this holds true across all steel types (perhaps a big if) that would mean that low wear resistance steels would get more of an increase percentage-wise than a high wear resistance steel. In other words, an increase from 200 to 232 TCC with a 2 Rc increase is more significant than from 800 to 832. There were some cases due to test variability where there wasn’t much difference in TCC with hardness. Here are a couple examples with clear trends:

There aren’t enough significant hardness comparisons in the data to say much else definitively. I would imagine that the improvement in TCC with increase in hardness would be greater with low edge angles since there is a larger spread of values among steel types with low edge angles. But quantifying that is difficult with the current dataset. The increase of 15.8 mm per Rc is also within range of another independent study performed with CPM-M4 [5]. Ignoring one potential outlier, the increase with hardness was 12.8 mm per Rc.

The CATRA test uses a fixed load and has little lateral stress on the edges of the knives. In “normal” cutting by humans there are larger stresses on the edges which can lead to edge rolling or chipping, especially with thin and low angle edges. Those effects are largely not seen with CATRA and therefore this measured effect of hardness is largely due to an increase in wear resistance. In cutting by humans or in cutting of hard materials there may be a stronger effect of hardness due to other mechanisms like edge rolling.

From the article:
The coefficient for hardness of 15.8 means that the regression predicts an increase in ~16 mm TCC for each point of hardness (Rockwell C). If this holds true across all steel types (perhaps a big if) that would mean that low wear resistance steels would get more of an increase percentage-wise than a high wear resistance steel. In other words, an increase from 200 to 232 TCC with a 2 Rc increase is more significant than from 800 to 832. There were some cases due to test variability where there wasn’t much difference in TCC with hardness. Here are a couple examples with clear trends:

There aren’t enough significant hardness comparisons in the data to say much else definitively. I would imagine that the improvement in TCC with increase in hardness would be greater with low edge angles since there is a larger spread of values among steel types with low edge angles. But quantifying that is difficult with the current dataset. The increase of 15.8 mm per Rc is also within range of another independent study performed with CPM-M4 [5]. Ignoring one potential outlier, the increase with hardness was 12.8 mm per Rc.

The CATRA test uses a fixed load and has little lateral stress on the edges of the knives. In “normal” cutting by humans there are larger stresses on the edges which can lead to edge rolling or chipping, especially with thin and low angle edges. Those effects are largely not seen with CATRA and therefore this measured effect of hardness is largely due to an increase in wear resistance. In cutting by humans or in cutting of hard materials there may be a stronger effect of hardness due to other mechanisms like edge rolling.

 

[Larrin]

There weren't enough hardness values, particularly within a single steel, to get more accurate hardness analysis.

 

[Revolverrodger]

It would be great if other companies would add to your database

Eventually with more solid data on edge retention, edge stability, toughness etc... the ideal blade steel may be identified for different applications (choppers, folders etc)

There weren't enough hardness values, particularly within a single steel, to get more accurate hardness analysis.

 

[DeadboxHero]

Vanadis 4 extra

−157+15.8×60−17.8×30+26.6×8.2

= 475 predicted Total cards cut at 60hrc with a 30° inclusive angle

Now if you increase the HRC by one point but keep the geometry the same it looks like this.

61hrc=490
62hrc=506
63hrc=522
64hrc=538

Now if keep the HRC at 60 but lower the geometry by 1° degree it looks like this.

29°=492
28°=510
27°=528
26°=546

The edge angle has more effect then HRC but you need hardness to support thinner edges. Vanadis 4 extra is a good steel to pick for this too because it hits a nice sweet spot with having enough alloy to get very hard and yet not so much that it's incredibly brittle. It's a very stable steel at high hardness but not as wear resistant as others.

16mm doesn’t seem like alot
I tend to recall ( maybe I’m wrong) that hrc is an exponential scale... I would have expected a larger effect

Did you account for interactions between variables in your linear model?

Very interesting analysis by the way