Cutting tests w/4 knife steels

[Phil Wilson]

I recently posted a reference to some cutting tests I made some time ago on several popular knife making steels. This was a general ranking of cutting ability on manila rope. I now have 4 similar fillet knives with different steels so decided to go back and do some more cutting to a provide more specific results. I cut manila rope using Wayne Goddard’s method. Wayne has been doing this for probably 30 years and has developed this test method to the point where he has a lot of confidence in it. I like the idea of cutting rope since it closely replicates the abrasive characteristics of deer/elk hair and wild pig bristles. I have found that my cutting tests on this medium will predict how the steels will actually perform in the field. The rope I cut was aprox. 5/8 inch diameter and had a plastic tracer strip running through it. I used one 5/8 inch strand separated out of a 3 strand rope. I use a slicing cut with downward pressure against a clean Alder wood board. The board is on a scale to indicate how much pressure is applied. The knife blades are all about the same spine thickness and flat ground to .006 to .008 behind the final sharpening bevel. Blade length is 8 to 9 inches but I marked each blade so that the cutting was done with 7 inches of the total length. I judged the blade dull when it would not cut through the final rope fibers with less than 20 pounds force against the board. I could also feel the smooth spot on the blade with my thumb. The aggressive grab is lost at this point. All knives were initially sharpened with a medium Norton silicon carbide stone, followed by a fine silicon carbide stone and then back stropped on loaded leather to remove the burr. When the cutting was done all blades would still slice cardboard with ease but left a little fuzz on the edge of the cut. They would also slice paper without stalling. I did not observe any edge chipping on any of the blades. The edge would still be useful in the field and in my experience work fine for filleting fish like Salmon or Striped Bass or for skinning a deer or elk. I admit there is some “feel” factor here. On the other hand after doing a lot of these tests one can almost predict the results with the first few cuts on the rope. I compare notes with others who do the same kind of testing and even if we get more or less total cuts that we agree very close over all. The steels compared are as listed below:

CPM S30V (RC 61)
CPM 154 (RC 62)
154 CM (RC 61)
12C27 (RC 59)

Hardness values are +/- one point as measured on my hardness tester calibrated with a Certified “Rockwell” test block. These values I consider optimum for each steel for a fillet knife and will work fine for all slicing type uses. I do my own heat treating and all blades were given a 2 hr Cryo cycle in LN2 and triple tempered. Heat treat details on all of the steels are available on request via e mail.

Results:
Cuts
CPM S 30V 210
CPM 154 150
154 CM 110
12C 27 80

Notes:
The S30V blade lost some initial sharpness at 60 cuts but there was no detectable change past that up to 150. After 150 it kept cutting but with more force up to 210 cuts where it took 20 pounds force to cut the final strands
.
The CPM 154 and 154 CM blades were pretty close the whole test. Both dulled at a fairly constant rate up to about 80 cuts. Above 80 it took increasing pressure up to 20 pounds before they were judged dull. The CPM 154 blade did 40 more cuts than the 154CM blade but was 1 point harder so a little better performance could be expected. The 154 CM blade had a better bite on the rope as it dulled. This is predictable based on the courser grain structure and larger carbides.

The 12C27 blade peaked out at 90 cuts and 20 pounds pressure. This is pretty close to the performance of the 154CM blade above. It is one point softer at 59 so again this could be predicted. On an earlier test with a different 154CM blade the 12C27 did 20 cuts more.

Conclusions:
All the blades dulled in a linear fashion, indicating that dulling was by wear rather than the edge rolling or breaking off. This indicates to me that the hardness and heat treating are in the correct range for knives used for the intended purpose. The S30V blade was a significantly better cutter, telling me that the extra expense for the steel and work to finish the blade are worth the effort for a long wearing working knife for cutting abrasive materials. The CPM 154 bested the 154CM by 40 cuts. This is enough of a difference to indicate that the CPM version is a clear improvement over the old formula. In addition the CPM version is easier to heat treat. There is no need for an oil quench and it is easy to get one point more hardness with the same soak temperature. The 12C27 performance was pretty close to the154 CM and it did so at one point softer. This is also a nice steel to work with and may have better overall toughness than the others tested here.

Qualification
These results are with my heat treating and edge geometry. I have found that blade thickness, grind angle, type of grind, sharpening, heat treating and hardness will have a great influence on cutting ability. I have also found different batches of rope to vary greatly in abrasive resistance. These tests were done with almost identical knives but as we know it is very difficult to make the same knife twice. This is just one point on the curve in evaluating all the great steels we have to work with.

PHIL

 

[Larrin]

Thanks, Phil, some very interesting and useful information. It makes me even more excited for the future testing Darrin and I are planning on doing with AEB-L, 12C27, and 154CM.

 

[Dog of War]

Phil - that's one of the best and most informative posts I've ever read. Clear, concise, very well-written ... are you sure you're a knife maker, and not a technical writer?

Thank you very much for your time and effort.

 

[redhawk44p]

Thanks. That was enlightening.
I hear Cliffs foot steps coming.

 

[db]

Very interesting. They all seem to be very close at losing the initial sharpness. S 30V at 60 and the154 at 80. I have to wonder those who keep there knives very sharp and can sharpen them that way, would they ever go beyond those points without a touchup? If not these results mean different things to different people.

 

[Phil Wilson]

db, Yes I think also that it is different steels for different jobs. For example field dressing and skinning an elk on the side of a mountain in a snow storm when it is getting dark, you don't want to stop and sharpen your knife. You want a blade that will keep cutting even though it is not as sharp as you normally would want to keep it. On the other hand working in the kitchen where some chopping might be done you want a blade that is tough but may loose its edge a little quicker but you can whip out the steel and tune it up pretty quick. CPM 10V would work better on the elk and 12C27 would work better in the kitchen.

Dogs of war, Yes I am a knife maker but a retired engineer who spent a lot of time writing criteria for experiments and reports on work that was done in order to get paid.

PHIL

 

[Cliff Stamp]

Nice work Phil, a detailed description of what was done and benchmarks.

I judged the blade dull when it would not cut through the final rope fibers with less than 20 pounds force against the board.

What was the starting force? What was the sharpening angle? Did you notice any significant difference in sharpening behavior both initially and after the cutting?

The 12C27 blade peaked out at 90 cuts and 20 pounds pressure.

Is this a typo as the table lists 80.

On an earlier test with a different 154CM blade the 12C27 did 20 cuts more.

Did you mean "a different 12C27 blade" there? On that note, in general how well would you estimate the spread of these results, how close to you think you could get if you did the same thing with different blades? Interesting results with the 12C27 vs 154CM as these are two radically different steels. I'd be interested in the heat treatment of 12C27 when you get a chance to email. There has been some contention of late as the ease of getting 58 HRC in 12C27m on a production level and it has a lower max hardness than 12C27. For a fillet knife it might be interesting to try a 12C27m/13C26 laminate. In general I think that would be an interesting composition.

The S30V blade was a significantly better cutter, telling me that the extra expense for the steel and work to finish the blade are worth the effort for a long wearing working knife for cutting abrasive materials.

Yes, it is a nice high wear stainless, have you tried it with the secondary hardening? Have you tried any ZDP-189 yet?

In addition the CPM version is easier to heat treat. There is no need for an oil quench and it is easy to get one point more hardness with the same soak temperature.

Do you know if the formulas are the same? Given Crucibles use of nitrogen it would not be surprising to find a small amount 0.1% or so in CPM154CM and possibly similar amounts of vanadium as in RWL34. Do you notice and difference in grinding/finishing the P/M version of 154CM.

I have also found different batches of rope to vary greatly in abrasive resistance.

Yes, cardboard is even worse. Chopping woods is insane in that regard, once you do a lot of that then everything looks excellently consistent, evaluating axes takes a decent amount of time - having a wood stove helps.

-Cliff

 

[Phil Wilson]

What was the starting force? What was the sharpening angle? Did you notice any significant difference in sharpening behavior both initially and after the cutting?

Starting force was 10 to 12 ponds, all knives resharpend normally by going back to the medium stone and then the fine. The blades are flat ground down to .006-.008 and then sharpened at about 12 degrees between the back of the blade and the stone

Is this a typo as the table lists 80.

Yes the correct number of cuts should be 90, I don’t know how to go back and correct this at this point.

Did you mean "a different 12C27 blade" there? On that note, in general how well would you estimate the spread of these results, how close to you think you could get if you did the same thing with different blades? Interesting results with the 12C27 vs. 154CM as these are two radically different steels. I'd be interested in the heat treatment of 12C27 when you get a chance to email. There has been some contention of late as the ease of getting 58 HRC in 12C27m on a production level and it has a lower max hardness than 12C27. For a fillet knife it might be interesting to try a 12C27m/13C26 laminate. In general I think that would be an interesting composition.

No I meant a different 154Cm blade. I think the spread would be about 10-12 cuts. I went back and repeated the cutting with the 12C27 blade and got 95 this time. Different blades would give different results but I think the overall conclusions would end up the same. I was looking for significant differences. In this case I can conclude that (1) S30V cutting this kind of material, with this hardness, blade geometry and sharpening technique out cut CPM 154, 154Cm and 12c27 at their optimum hardness. (2) CPM 154 will do better than the older grade by enough to be able to tell the difference in the field. (3) 12C27 at a lower hardness did better than I expected and is kind of in the same category as 154 Cm. you probably would not be able to tell the difference in the field especially if you are fussy about sharpness. Yes laminates are interesting, do you mean Damascus type or one harder steel in the center. The truth is I am full up right now and its all I can do to concentrate on those steels I know work. The heat treat I used for 12C27 is simple: preheat at 1500, ramp to 2020, hold 20 min. Oil quench to room temp. 2 hr in LN2, double temper at 380 for one hr each time, final temper at 350 after finish grinding and polishing. Final hardness was an honest 59+.

I have tried the secondary hardness heat treat on CPM S30V but didn’t find that it was any better than the lower cycle. At least on the type of testing I do and the knives I make.

I have talked a little with Crucible about CPM 154 and understand there is some Vanadium in the mix and probably Nitrogen. I didn’t press them since I am sure it is proprietary to some extent. It does have a higher attainable hardness and is much easier to heat treat than 154CM. 154CM is a PITA to get to RC 61. I have said this many times before. Paul Bos helped me out with this about 15 years ago. He has it figured out. There does not seem to any difference in grinding and finishing between the two. The new one satin finishes nice and the guys who buff it will find it polishes with out the visible (D2 like) grain structure that 154Cm has. I will now only use CPM154 and not have to fight the old stuff anymore. It will be the standard for fillet knives and kitchen knives. S30v will be my upgrade for fillet knives, and S30V, S90V, and 10V will be for hunter/utility blades.
I have used ZDP 189 and reported briefly on this before. The edge holding is great and seemed easy to heat treat. It performed close to CPM S90V. It is very difficult to get the steel. I had my son in Japan bring me some. They will not export it to a private party at least that is what they told him. It is also very difficult to get any tech support on heat treating. So I gave up on it. I will stick with S90V.

I do want to do more work with 12C27, AEB L and others. They are simple, easy to work with and make nice blades. I think they would be great for kitchen knives. However the reality is that CPM 154 seems to do everything they do and a little more and I get great tech support from Crucible and I can get the steel in any size and quantity I want in 5 days after I order it.

One last thing, I said that the cutting was linear on the tests. Of course it is not it just feels that way to me. Your testing proves that if you take enough points that these steels dull on a curved line.



PHIL

 

[Larrin]

I do want to do more work with 12C27, AEB L and others. They are simple, easy to work with and make nice blades. I think they would be great for kitchen knives.

Hey Phil, I got something extra special to send you in the mail tomorrow, and no, it's not a bomb. It does come in two thicknesses though, both sizes in something like 14x11".

 

[M Wadel]

a bit offtopic but how much does a hardnesstester cost, and who sell this equipment?

 

[Cliff Stamp]

12C27 at a lower hardness did better than I expected and is kind of in the same category as 154 Cm.

Very interesting behavior as you would expect the edge behavior of these steels to be very different so there are obviously multiple forces at work which are having a cancellation effect.

Yes laminates are interesting, do you mean Damascus type or one harder steel in the center.

I was thinking of a core because then you could get the higher corrosion resistance/toughness of 12C27m with the higher hardness/wear resistance of 13C26. This however may defeat one of the obvious benefits of these steels which is low cost.

Final hardness was an honest 59+.

That is interesting as that is exactly what you would predict given the carbon content and a soak which put all of that carbon into solution by looking at the temper responce of a pure carbon steel. Have you tried lower tempers?

I do want to do more work with 12C27, AEB L and others. They are simple, easy to work with and make nice blades. I think they would be great for kitchen knives. However the reality is that CPM 154 seems to do everything they do and a little more and I get great tech support from Crucible and I can get the steel in any size and quantity I want in 5 days after I order it.

Doesn't cost really favor the Sandivk steels though as you can find those steels on $5 knives. Given the performance of 12C27 it would be expected that 13C26 may compete with CPM-154CM or at least bridge that gap someway, and it has to be way cheaper than the P/M steel. I'd be very curious about a push cutting comparison but for a people who hint/fish a draw is significant and thus the slicing rope cuts are more relevant.

The participation of Crucible is very nice. I have sent dozens of emails for request on steels from various companies with very little interaction. Crucible is much more responsive even to general questions in which it is clear you are not intending to buy mass quantities of their product. I recently had an email exchange with a steel company and the first question was "What volumes are we talking about?" and when I answered basically none that was the end of the conversation.

...if you take enough points that these steels dull on a curved line.

Yes, it depends on how you look at it. The graphs are essentially of two stages and you can approximate the curves well by essentially two straight lines. Most people with really high standards of sharpness don't tend to move off the first line because by the time you move into the second one you can see the blade glinting and the edge is starting to deform/chip on a sub mm scale and it is usually much better to sharpen than to let that damage propogate and weaken the edge.

Is there any chance of this getting into an article for Tactical knives or Blade? It would be nice to get some wide circulation on quality performance information on those steels.

-Cliff

 

[Larrin]

Doesn't cost really favor the Sandivk steels though as you can find those steels on $5 knives. Given the performance of 12C27 it would be expected that 13C26 may compete with CPM-154CM or at least bridge that gap someway, and it has to be way cheaper than the P/M steel.

Sandvik isn't any cheaper. Sandvik doesn't generally sell 13C26 in knife sizes, the knife companies using it are probably getting it in a very sizeable amount. Uddeholm is a little better at selling in smaller quantities, but I believe the last time we bought some AEB-L we had to get 500 pounds and it took 12 weeks.

Edit: I just talked to my dad and he said you might be able to purchase in smaller quantities. It sure would be nice if somebody like Admiral Steel would get interested, though.

 

[Larrin]

I was thinking of a core because then you could get the higher corrosion resistance/toughness of 12C27m with the higher hardness/wear resistance of 13C26. This however may defeat one of the obvious benefits of these steels which is low cost.

If you want anyone to make such a steel you'd need to talk to Devin Thomas.

That is interesting as that is exactly what you would predict given the carbon content and a soak which put all of that carbon into solution by looking at the temper responce of a pure carbon steel. Have you tried lower tempers?

With our AEB-L we usually austenitize at 1925F and then temper at 350 or 375F to get 60 Rc. If a 1975 austenitizing temperature is used the temper is 375 or 400F to get 60. Darrin says he has occasionally had to temper as high as 425 or 450F. This is of course with cryo.

The participation of Crucible is very nice. I have sent dozens of emails for request on steels from various companies with very little interaction. Crucible is much more responsive even to general questions in which it is clear you are not intending to buy mass quantities of their product. I recently had an email exchange with a steel company and the first question was "What volumes are we talking about?" and when I answered basically none that was the end of the conversation.

Crucible is by far the most friendly to the knife market. I love Crucible.

Is there any chance of this getting into an article for Tactical knives or Blade? It would be nice to get some wide circulation on quality performance information on those steels.

As you know, we hope to publish some testing in Blade, but I sure wish things like this didn't take so much time; and we haven't contacted Blade at all anyway, but they'd be crazy to turn down the kind of testing we want to do.

 

[barrabas74]

Wow this has been a very informative post, thanks guys.

 

[M Wadel]

at this place you can get AEB-L and 12c27 and marss500(12c27mod) in small quantities, but its located in sweden so i dont know what the total cost would be http://nordellknives.com/indexx.shtml 100skr=13.55us$

 

[hardheart]

Hey Phil, I got something extra special to send you in the mail tomorrow, and no, it's not a bomb. It does come in two thicknesses though, both sizes in something like 14x11".

we can make it like a passaround, you can send it to me after you're done with it.

of course, that's where the passaround would end...

 

[Cliff Stamp]

Sandvik isn't any cheaper.

This seems odd considering the price of the knives that use it. It may be just a volume issue so it may be that a maker needs to serve as an intermediate like Simonich did with Talonite.

With our AEB-L we usually austenitize at 1925F and then temper at 350 or 375F to get 60 Rc. If a 1975 austenitizing temperature is used the temper is 375 or 400F to get 60.

Why 60? What happens to the performance if you soak at 1975 F and temper at 325 F?

-Cliff

 

[Larrin]

This seems odd considering the price of the knives that use it. It may be just a volume issue so it may be that a maker needs to serve as an intermediate like Simonich did with Talonite.

Talking to my dad he says that Sandvik is actually more expensive.

Why 60? What happens to the performance if you soak at 1975 F and temper at 325 F?

To the first question: it's a good round number. To the second: I don't know.

 

[M Wadel]

nordellknives charges about 9-9,50€/kg for AEB-L

 

[Cliff Stamp]

Thanks, according to :

http://www.nordellknives.com/indexx.shtml

RWL34 is way more expensive than AEB-L, which seems sensible given it is a P/M with a much higher alloy content.

If I am reading the numbers right it looks like a piece of AEB-L to make a knife is about $5 which would seem reasonable because there are really inexpensive Scandinavian 12C27 and 12C27m blades.

-Cliff