Some comments on ZDP-189 vs VG10 edge retention

knarfeng

knarfeng

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A while back there was a thread asking about VG10 and ZDP189. Dennis Strickland posted that he could not really tell the difference between them when cutting cardboard. Several others posted similar experiences.
http://www.bladeforums.com/forums/showthread.php?t=730207

Dennis and I talk a bit on the side and he wanted to know if I was interested in doing some further testing. I said the equivalent of "(expletetive deleted) YES". Dennis was kind enough to loan me his knives and let me test them using 3/8” manila rope as a medium. (I doff my cap to Dennis, who let me borrow ~$250 worth of cutlery for a month without a blink.)

Description of test:
My test is such that the only variables are the alloy, hardness and edge angle. I sharpen the knives to the same edge angle, so that leaves hardness and alloy as the variables to be tested. I make slicing cuts through the manila rope without coming in contact with the supports, then examine the edges for deformations using a 3X hand lens and a high intensity lamp. Phil Wilson has said that cutting manila rope is quite predictive of a blade's performance in real world usage.
http://www.bladeforums.com/forums/showthread.php?t=421773

Blade information:
I started by measuring the Rockwell hardness of each blade. So we end up with this information about the knives.

Spyderco Stretch II: Full Flat Grind ZDP-189__62HRC
Spyderco Endura : __Full Flat Grind VG10- ___59HRC

I measured the blade thickness just above the bevel of each blade. Both were in the range of 0.027” – 0.031” depending on where I measured. (The thickness has no impact on my test results, but it can if you cut cardboard. I include the information for completeness.)

For this test, I rebevelled the edges to a uniform 15° per side and sharpened them using DMT diamond stones (extra-coarse for the angle change, then Coarse, Fine, and Extra fine.) I checked each blade with the lens to ensure that I could not see the edge.

Test results:
I made two complete runs, the results were the same with each, I will summarize below:

I made 20 slicing cuts with each blade through 3/8" manila rope and examined the edge.
For the ZDP-189 I could see nothing.
For the VG10 I could see a few glints.

At 40 cuts I stopped and examined the edges again.
For the ZDP-189 I could see a few glints.
For the VG10 I saw an increased number of glints, and there were sections where I could see a length of edge. I could not tell any difference between the two regarding the force required to make a cut.

After 60 cuts
A very faint line was visible along the ZDP-189.
A shiny line was definitely visible on the VG10. I could not tell any difference between the two regarding the force required to make a cut.

After 80 cuts
The faint line on the edge of the ZDP-189 was more visible, but not shiny.
The line on the VG10 was shinier than it had been at 60. I could not tell any difference between the two regarding the force required to make a cut.

After 100 cuts. Same as at 80

After 120 cuts. Same as at 100

After 150 cuts. VG10 still showed more shine.

At the end of 150 cuts I alternated between the two, making a cut first with one knife, then with the other. While the VG10 still cut the rope easily, I could feel a slight difference between the effort needed to cut with the two knives.

Conclusion:
So ZDP-189 actually does hold an edge better than VG10, but you have to do A LOT of cutting before the difference becomes noticeable in this type of cutting. If you needed to retain an absolute scalpel edge as long as possible, the difference would appear sooner. I'm not sure that I know what type of cutting that would be, but I'm sure somebody somewhere has such a need.

Comments:
As for me, with the types of cutting I usually do, I don’t think I’d ever do enough cutting to make the difference in performance between ZDP-189 and VG10 worth the price difference. But I would pay extra to get the Full Flat Grind. The difference won’t show up cutting rope, but it does when you cut cardboard. I did some of that as well. But that’s a wall of text for another day.

Cheers folks.
And a big THANK YOU to Dennis Strickland!

100_3091.jpg
 
a big thank you to knarfeng for all this work. although i've only been a member since last july i've noticed that there are lots of opinions on the edge durability of various alloys but only a few members actually do the dirty work.people really the only way we can know how capable our knives are is to cut & chop.we can study rockwells & compositions & make guesses but we need to get our hands dirty to really know what we have.me2 does a lot of testing however i'm not sure aluminum is as abrasive as cardboard & rope.whatever i ca'nt deny that me2 & some others really try to educate us to the durability of the knife steels. frank [knarfeng] is a working engineer & has access to instruments to give measurements on hardness & edge angles which certainly removes many variables from the test equation. being the perfectionest he is i'm certain he would agree with the premise that "one test is worth a thousand opinions." my cardboard tests along with franks contributions lead me to believe that vg10 represents a better value dollar wise than many of the more expensive alloys.i have had many knives in vg10 thru the years but did'nt realize what a good steel it was. also vg1 is certainly right up there close to vg10 in performance.be that as it may my traditional folders in gec 1095 make me quite happy.i really want to extend my gratitude to knarfeng for all this effort, in addition ankerson works his tail off chopping, however i think jim [ankerson] is'nt so much interested in proving edge quality as he is in destroying tons of wood.
 
That is a really low hardness for ZDP. It gets better around RC 64 and is about perfect at RC 64.5-65 IMO. It starts to pull ahead from VG10/154cm/ats 34, etc. at higher RC's without getting brittle. I've had more brittleness with 440C than ZDP to be honest.
 
The Mastiff said:
That is a really low hardness for ZDP. It gets better around RC 64 and is about perfect at RC 64.5-65 IMO. It starts to pull ahead from VG10/154cm/ats 34, etc. at higher RC's without getting brittle. I've had more brittleness with 440C than ZDP to be honest.
Click to expand...

I kind of expected a bit higher hardness as well, but it's an honest reading. The machine is calibrated with a standard traceable to the national standard. Be advised that all hardness readings are ±1, because that is the accuracy limit of the calibration standard. So all one can really say is that the hardness is 61-63.

One of the other comparisons I ran with Dennis's FFG Endura was a comparison between it and a Native III, VG10 measured at 59HRC. I have always contended that with this setup, the overall profile of the blade does not affect the results. I was able to confirm this with this comparison.

Same alloy, same hardness, same edge angle, different profile. The results were the same, showing that the profile is not a factor in these comparisons.

Profile is DEFINITELY a profile when you cut cardboard. More on that another day.
 
Thanks for the kind words Dennis. I mainly cut Al cans to irritate people here who think its not a real world test. That and after my steeling work, I'm out of cardboard. Do you think I'd get funny looks walking into an Ingles grocery store with a 9" blade M2 HSS Leuku and asking for all their cardboard?:D

I thoroughly enjoy the discussion of geometry in cutting endurance testing. I have reached some conclusions about cardboard cutting based on my sore arms and nearly unaffected edges that may have more to do with edge geometry (1.5" wide, 1/16" thick, full flat grind) than blade steel choice.

What is the difference between VG-1 and VG-10? Are they powder/particle steels?

I've recently tried hard to lower my OCD (not the real kind; much sympathy to anyone suffering from the real thing.) about really sharp edges. I tried not to resharpen during my cardboard cutting until the knife wouldn't cut paper, but that point never came. Did the knives in this test ever reach that point? That's when normal people (not us here) consider a knife to be dull, and IME at that point it is pretty much useless as a cutting tool. Did they ever get to the point they wouldn't cut the rope without a lot of weight and effort? A slight glint at magnification under strong light will still shave hair off my arm if I do it just right.

Knarfeng, how were you able to get around the testing of angled surfaces near the edge? Do you have a table with an angle adjustment on it, that would be the envy of knifemakers everywhere, or at least in the shoptalk forum? I had to learn the hard way. Did you know diamond indenters squeak like rodents right before they crack?:eek:
 
Great review, Frank! Thanks for sharing your investigation with us. And thanks, Dennis, for loaning out the knives.

Love the picture at the end, too - both knives are classy in their own ways.

me2,

VG-1 has 0.95-1.05%C, 13.0-15.0%Cr, 0.2-0.4%Mo, and 0.25% or lower Ni making it similar to 19C27 from Sandvik, Ginsanko from Hitachi, and MBS-26 from Masahiro (probably rebranded VG-1 as they're not a foundry).

VG-10 has 1.0%C, 15,0%Cr, 1.0%Mo. 0.2%V, and 1.5%Co making it, well, not similar to those other steels.

Well, that's what they say here: http://e-tokko.com/eng_original_list.htm

Both steels are great with VG-10 offering more wear-resistance and VG-1 offering a finer grain (easier sharpening and less likely to microchip compared to VG-10). Neither are 13C26, but they're still nice.
 
knarfeng said:
Profile is DEFINITELY a profile when you cut cardboard. More on that another day.
Click to expand...


Edge profile or angle makes a ton of difference when cutting cardboard, also blade thickness and grind. :) :thumbup:

On my cardboard knife (Voyager) I put a 15 Degree per side edge on it as I did for all the other knives I tested cutting cardboard. :thumbup:
 
me2 said:
Thanks for the kind words Dennis. I mainly cut Al cans to irritate people here who think its not a real world test. That and after my steeling work, I'm out of cardboard. Do you think I'd get funny looks walking into an Ingles grocery store with a 9" blade M2 HSS Leuku and asking for all their cardboard?:D

I thoroughly enjoy the discussion of geometry in cutting endurance testing. I have reached some conclusions about cardboard cutting based on my sore arms and nearly unaffected edges that may have more to do with edge geometry (1.5" wide, 1/16" thick, full flat grind) than blade steel choice.

What is the difference between VG-1 and VG-10? Are they powder/particle steels?

I've recently tried hard to lower my OCD (not the real kind; much sympathy to anyone suffering from the real thing.) about really sharp edges. I tried not to resharpen during my cardboard cutting until the knife wouldn't cut paper, but that point never came. Did the knives in this test ever reach that point? That's when normal people (not us here) consider a knife to be dull, and IME at that point it is pretty much useless as a cutting tool. Did they ever get to the point they wouldn't cut the rope without a lot of weight and effort? A slight glint at magnification under strong light will still shave hair off my arm if I do it just right.

Knarfeng, how were you able to get around the testing of angled surfaces near the edge? Do you have a table with an angle adjustment on it, that would be the envy of knifemakers everywhere, or at least in the shoptalk forum? I had to learn the hard way. Did you know diamond indenters squeak like rodents right before they crack?:eek:
Click to expand...

They are both melt alloys. No PM. I've only done a quickie edge retention comparison of VG1 and VG10. In that test I was unable to tell the difference between the two when it comes to edge retention.


I genius I am not. Both knives have a flat area near the tang. You can kind of see it in the picture of the Stretch. I measured there. I can't do that for most traditionals. Those folks usually anneal the tangs. But makers of one-handers typically don't.

OUCH! Tell me you did not find that out the hard way!
(I test under the watchful eye of the Lab metallurgist. I am sure he would never let me find that out the hard way.)
 
Tom, thank you for the kind words. They are significant to me.
Frank
 
Nice testing Frank, is there a chance to repeat with lower edge angles?
I have a Tojiro which is 62HRC and compared to ZDP-189 in another knife 64-66hrc it is more chippy, they're also at 15 per side, but I'm lazy to thin down long blade :)
 
although i'm sure frank would be happy to do more tesrs but trying out all these alloys at different rockwells & different angles could make this a not pleasant venture. as to alloy hardness-- we are interested in what the knives do as they come from the factory. afterall how many customers are going to be able to custom rockwell a factory blade. this was a realistic test on an as issued realistic product. i Am only too happy to have someone to do all the work involved as it were.however i certainly welcome all formites to post their own test results with as many established variables as they desire.
 
knarfeng said:
I kind of expected a bit higher hardness as well, but it's an honest reading. The machine is calibrated with a standard traceable to the national standard. Be advised that all hardness readings are ±1, because that is the accuracy limit of the calibration standard. So all one can really say is that the hardness is 61-63.

One of the other comparisons I ran with Dennis's FFG Endura was a comparison between it and a Native III, VG10 measured at 59HRC. I have always contended that with this setup, the overall profile of the blade does not affect the results. I was able to confirm this with this comparison.

Same alloy, same hardness, same edge angle, different profile. The results were the same, showing that the profile is not a factor in these comparisons.

Profile is DEFINITELY a profile when you cut cardboard. More on that another day.
Click to expand...


Thanks for showing your results, very easy to understand. I wish you would publish more of your testing here.

About cardboard cutting, would you think a thick bladed knife that requires more force to push through cardboard also reduces the edge retention compared to same HRc in same steel and grind but thinner stock? Or only the force required to cut is increased?
 
PatriotDan said:
Thanks for showing your results, very easy to understand. I wish you would publish more of your testing here.

About cardboard cutting, would you think a thick bladed knife that requires more force to push through cardboard also reduces the edge retention compared to same HRc in same steel and grind but thinner stock? Or only the force required to cut is increased?
Click to expand...


That wouldn't have any effect on edge retention.

The thicker blade would just require more force to go through the cardboard.
 
Ankerson said:
That wouldn't have any effect on edge retention.

The thicker blade would just require more force to go through the cardboard.
Click to expand...

I think it would have the effect on edge retention, and the thinner the edge, the more pronounced the effect will be.
It's just physics + human behavior or nature. You can't hold knife perfectly perpendicular to the cardboard or cutting medium all the time, plus small irregularities in the cardboard itself. Therefore, lateral forces are created on the edge, in other words that's how the rolls form, and stronger the force you use to make a cut, stronger those lateral forces are, thus more and larger deformations of the edge, thus edge holding gets affected, negatively :)
 
Gator97 said:
I think it would have the effect on edge retention, and the thinner the edge, the more pronounced the effect will be.
It's just physics + human behavior or nature. You can't hold knife perfectly perpendicular to the cardboard or cutting medium all the time, plus small irregularities in the cardboard itself. Therefore, lateral forces are created on the edge, in other words that's how the rolls form, and stronger the force you use to make a cut, stronger those lateral forces are, thus more and larger deformations of the edge, thus edge holding gets affected, negatively :)
Click to expand...


The edges were the same profile.....

The blade thickness was different.
 
You lost me there...
What I said was that the force, especially the lateral force has the rolling (or deforming) effect, just on thicker edges it's less pronounced, because the edge is stronger.
Basically, with the same edge angle, thicker blade in cardboard would've dulled quicker, because greater force needed to be applied. How big the difference would be is another test, and it'd require 2 knives from the same steel, same HT, same edge angle and just different thickness.
 
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