A Tale of 2 heat treat's (or why one ATS34 knife chips, and one doesnt)

Bladeandbarrel

Bladeandbarrel

Joined
Oct 5, 1998
Messages
3,148
So, I'm sitting in a seedy restaurant doing a little kibbitzing and out comes my muy grande 18 ounce porterhouse.

I cut this artery clogging steak in half and decide to use my EDI GENESIS one one half, and my AXIS on the other. Both plain edge.

After cutting this monster steak, with ease and alacrity I might add(yum yum)
and stuffing myself, I examine the edges of both knives.

Lo and behold my AXIS wonderknife has taken on a very micro-serrated quality (apparently tiny chips from the ceramic plate), while my Genesis' polished edge remained polished, and sharp with no rolling or turning.


Hmmmmn.....

Maybe there is something to ATS34 at a lower "medium well" Rc of 57-59, compared to BM's "well done"61?

Or is the EDI cryo treatment better?


This will take much more intense scientific research
(ummmm please pass the rolls..)


+++++++++++++++++++++++++++++++++++++++++++++

"The most effective armor is to keep out of range" -Italian proverb

[This message has been edited by Anthony Lombardo (edited 20 May 1999).]
 
Oh, I forgot, the BM slightly deforms on a brass rod, while my Gensesis blade will not.

All day long I have been trying to figure out how to get a Genesis blade in an AXIS handle. So far no dice.
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The lower RC blade should have higher toughness which matches what you experienced. However the higher RC has an increased wear resistance. Try cutting something really abrasive and the Axis should stay sharp longer.

-Cliff
 
I have long had this trouble with Benchmades but not with my own knives in ATS-34. I personally think that BM is (or was - the knives I know are fairly old) treating their steel too hard. Just sharpening my AFCK I get a feel and a sound that I don't care for, as if I were sharpening something crystalline, like another piece of ceramic. With knives I've made in ATS-34 (treated by Texas Knifemaker's Supply) I don't have this problem at all. They whip right up into a shaving edge and feel and sound nice doing it. I have a strong suspicion this is because they are treated slightly softer.

I think that some companies may go for the higher Rockwell number because it's an easy, measurable way to show the less informed customer how this steel is better than, say, 440C. But I suspect that ATS-34 would give better overall performance (meaning edge-taking, edge-holding, and ease of sharpening) if it were slightly softer than the production norm.

------------------

-Corduroy
(Why else would a bear want a pocket?)
 
I have always seen Benchmade's ATS-34 as over-cooked. When people really don't like Benchmade, one of the most common things I hear is that the edge chips or the tip broke.

Mark McWillis once told me that Benchmade does cryo their blades.

They do hold an edge well if you stay away from hard materials though.

Loved your recent articles. You know what we want to read.

Harv
 
Cliff,

I see your point-BUT-Think about objects that are cut on a daily basis.

How many are "Abrasive"? Cardboard comes to mind...

Rope certainly isn't, neither are wood, animal flesh, envelopes, or fabric, yadda yadda yadda...


A better pocketknife strength from where I sit, may be toughness. For example should an edge crinkle under pressure, or when it hits a staple in a box? If you cut a large amount of foodstuff (generally non abrasive), what it more important-the ability for an edge to withstand the dulling(edge curling) effects of a cutting board, or be able to withstand abrasion?

Granted, there must be a happy medium between toughness and abrasion resistance at some point. At this stage, I am voting for toughness being more important than the two.
 
Thanks Steve, (apparently we were posting simultaneously)


I will start by saying I have learned more in the last year from you, Joe T., Cliff,
JKM, RJ Martin, and Darrel Ralph about the real guts of practical knifery and their testing.

The point I was trying to make with my post was that maybe toughness was a great advantage for a pocketknife over wear resistance. I can always resharpen a dull
edge, but a chipped one is quite a different kettle of fish.

My other point was to show that you cannot judge a book by its cover. Although the AXIS and the GENESIS are both flat ground of the same material, at the same thickness, they perform differently in the field despite similar edge geometry. If anything, the Genesis is measurably thinner and should be the first to chip out under stress, but wasnt.

Actually, using the brass rod and heavy pressure, I have a hard time making any kind of a mark on the edge of 2 different Genesis'.

 
I don't doubt that these two companies heat treat their steel differently. This would greatly affect the toughness. However, considering the normal motion for cutting a steak (at least the way I do), I doubt you'd really be putting all that much stress on the blade itself. At least, not enough that it should chip. Is this maybe due to the method of sharpening - the axis being slightly more coarse?

I may be wrong here - if the knife is truly chipped, then that is somewhat strange. Were you actually striking the plate hard when you made a forward stroke with the knife? This is the only way I can see that any quality knife should become chipped in such a situation.




------------------
JP Bullivant
 
jpbulli, I doubt Anthony's 710 actually chipped, the edge just got microserrations and became more coarse. All of which indicate that it would chip easier.

[This message has been edited by JoHnYKwSt (edited 20 May 1999).]
 
Actually micro-serrations would be a better term than chip because metal wasnt actually lost, just "Moved" and peened.
Read the original post it says "micro-chips"

Yes, cutting on the plate did it.
Maybe cutting the steak off the bone contributed. At the time I was entirey too consumed by gluttony to notice.

Regardless, the edge is extremely rough and jagged and will no doubt require my speed sleeves to straighten out
The Genesis edge looks like new.
 
At least according to Ernie Mayer, his "lower temp cycle" heat-treat/temper process can yield better toughness at the SAME Rockwell as the "aircraft-industry standard".

As I recall, the aircraft standard was around 1950F then cool, then back up to around 950-975f-ish, back down, back up to 950-975, back down. It's a "three stroke process". There are also varying places to do sub-zero freezes and at least two ways of doing it, pure liquid nitrogen or the less intense "bury it in dry ice for 24 hours in an old freezer" - also known as "home brew cryo".

The Ernie Mayer method varies - it goes 1950f/375f/375f. Some people vary these a bit, I've heard of going as low as 1925f on the "first stroke", 350 on the 2nd and 3rd. This combined with a dry ice "home brew cryo" was how The Outsider was done; it's edge and secondary point survived battering a coconut into submission including hits to the counter
biggrin.gif
.

Can I "prove" the Ernie Mayer recipe is better? No. I wish. My personal intuition is that it's better. I have reasons for believing that that...I...can't go into here without veering into "personal attack" and...we've had this flamewar. Ask me in private.

I'll also have more evidence when I finish that sword...sigh.

Jim March
 
Anthony :

Granted, there must be a happy medium between toughness and abrasion resistance at some point. At this stage, I am voting for toughness being more important than the two.
Click to expand...

Depending on the blade I would agree, its the exact way I would go on a lot of knives. However, read rec.knives for awhile and you will come across a poster who makes knives out of 1095 steel, hardened to 65-68 RC. These will not be very tough but they are extremely abrasion resistant and for what he is doing they work great.

If you cut a large amount of foodstuff (generally non abrasive), what it more important-the ability for an edge to withstand the dulling(edge curling) effects of a cutting board, or be able to withstand abrasion?
Click to expand...

For me I would want high wear resistance unless I was doing some kind of chopping. My cutting boards are all soft though, no ceramics or similar.

Think about objects that are cut on a daily basis.

How many are "Abrasive"?
Click to expand...

This is the most important part.

I have a CPM-10V knife coming from Phil Wilson. It has a very high wear resistance and is hardened to 62.5 RC. Its charpy value should be very low - however for what I intend to do with it, I think it will work out ok. I will let you know how it turns out. I will be cutting a lot of wood, cardboard, ropes, webbing, plastics, food etc.

On the other hand I am mulling over a couple of CPM-3V blades with Mel Sorg. One of them will be a large machete type blade and the other a large BM class knife. In both of these I want the 3V left at its high charpy value rather than bumping up the RC to get the added wear resistance, for exactly as you described I don't want the edge to roll or chip.

So yeah in short it is very important to have the knife tough enough so that the edge does not roll/impact/chip, however it is important to note that how strong this needs to be is very dependent on what you are cutting. And to make matters worse not all steels behave the same way so RC is not a universal standard. Try to get the charpy value and even better, the elastic constants from the dealer/maker.

-Cliff
 
Just for the record, EDI's web page claims that the Genesis is Rc60. Is there really that much difference between 60 and 61?
 
Joel, there could be. CPM 420V goes from a charpy value of 22 to 12 when you go from 55/56 to 57 RC. That is a toughness loss of 50%. That much of differnence would be quickly evident. Note the tempering process is different between those two RC values which as Jim pointed out is very important.

-Cliff
 
I agree there's a happy medium somewhere in here. For folders, though, I lean more towards edge holding than you do, Anthony. For a truly general-use folder, cutting paper and cardboard will dull an edge quickly. For cutting food on a wooden cutting board, I don't care about toughness at all, really. There are lots of utility uses where I'd rather have edge holding, but some where I wish I had more toughness (I too have chipped a Benchmade ATS-34 knife pretty good).

Joe
jat@cup.hp.com
 
Joel,
per Will Fennell of EDI, Rc is actually closer to 58-59 after they did some testing.
He wont tell me their proprietary heat treat though.
frown.gif

A point on the Rc, especially 2 pts can make a huge difference.

Joe-
According to Dan Friel at Edgecraft corp., toughness is much more important than edge holding when cutting on a cutting board.
They have extensively tested kitchen cutlery and after looking at the edges under high powered microscopes, that 9 times out of ten, when a knife "dulls", it is because the edge has "failed"-either curled or rolled and fallen off. It is a direct result of the impact of hitting the cuttingboard, or plate etc etc.

Thats why the Chef's Choice sharpeners actually put a somewhat faceted convex edge on their blades-he feels it supports their edge the best, and one reason they make great edge-holding claims. They use a tough, proprietary blend similar to 154Cm, heat treat for toughness, rather than abrasion resistance, and sharpen with the "trizor" arched/convex edge. The very fine sharpened/honed edge is about a micron thick.
Similar to the edge on a new BM, or EDI, or Spydie. When I think about it that way, with one micron of metal at the apex of the edge, toughness seems very appealing.

So, do our edges fail outside the lab from "Abrasion" or from
"Impact"
When Wayne Goddard cut all that rope, did he use a cutting board? I bet he did...........

Maybe these very abrasion resistant steels we are using (440v, 420v) are great for cutting cardboard, but maybe not the best for all around use?

Does Abrasion resistance equal better edge-holding? Maybe-but maybe only if you are cutting cardboard.


[This message has been edited by Anthony Lombardo (edited 21 May 1999).]
 
Anthony --

That I believe. After all, a smooth steel wouldn't work otherwise. I figure having to steel occasionally is something that's necessary, and I don't even consider it in my edge-holding equation. Time between sharpenings -- when the steel stops working -- is what I'm looking for when considering kitchen use. But I definitely agree -- on a cutting board, with the kind of thin edge you want for food prep, the edge typically rolls.
 
Joe,

I am not trying to needle you, just trying to
fuel the discussion of our favorite subject....


How does the edge "stop working"
Is it from abrasion, or impact?
Or both? What is more important?

The edge is slightly thinner on the Chefs choice kitchen cutlery than say a GENESIS or AXIS, but why would the edge fail differently on each? The apex is still only a micron if the knife is .020 at the bevel, or .035 at the bevel.

(Where is RJ Martin when we need him most..)


[This message has been edited by Anthony Lombardo (edited 21 May 1999).]
 
Anthony :

Does Abrasion resistance equal better edge-holding?
Click to expand...

That is a very important question. The answer I think is yes on rope, cardboard, webbing, and food. However I would like to the results of any testing on the subject. It would not be difficult to test. Just take two identical knives and have them tempered differently and use them for awhile. One thing that very tough steels should have going for them is that they can take a very low included angle. So when you are testing them keep lowering the angle.

-Cliff
 
Well, this is where you and I disagree, Cliff.

Food is not abrasive.
Rope is not abrasive.
Plastic is not abrasive.

Rope-For example, when cutting a free-hanging rope, over time, the knife is NOT dulled by the edge being worn or polished AWAY. It dulls because the impact against the rope pushes the edge over and folds it, then it either stays curled or breaks off.

Food-I know of no known human food that is abrasive. That sounds like a stomachache to me. I have been told that cutting a bushel of corn is an excellent test of edge holding. That remains to be seen. Corn cobs are hard, they aren't abrasive.

Plastic-Definately NOT abrasive to hardened steel. ex-Kydex is not abrasive to metal, its what gets trapped in the kydex, usually grit from grinding belts that shape it/polish it. Fiberglass is a differnt story.
 
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