CPM S30V and hardning

[Clip]

This really has been a fascinating read. Thank you Cliff Stamp for going to such lengths to explain some of the fallacies inherent in our opinions about knives.

I agree with Fancier, this thread has been very informative. Studying this stuff is one thing, the way Cliff explains it is on a different level completely.

However:

It might even cure me of the compulsion to put so much emphasis on the type of steel used in a knife when I buy it, and might result in an overall reduction in the number of knives I feel compelled to purchase.

In my case, fat chance! It seems when I try to resist, the bug bites twice as hard.

[Cliff Stamp]

Spyderco aims it's s90v in around a range of 58-59 Rc and it's s30v at 58-60 Rc. so will there be any overlaps?

Yes, to clarify, lets assume :


1) both have been heat treated optimally

-austenization temp is minimal in time, and maximal in temperature
-at least 12% of chromium goes into solution
-fast quench (oil)
-cryo before temper
-temper to complete first stage tempering (low carbon martensite)

2) both have the exact composition as-spec'ed

3) the oven's (operators, etc.) are 100% without flaw

This will produce a near identical hardness in both and the same micro-structure the only difference being the carbide volume is much higher in S90V. In this ideal scenario :

-the will have similar compression resistance so the edges will dent / roll on a large scale the same, no advantage to either

-s30V will have better compression resistance on a micro-scale because it will have less carbide tear out, advantage to S30V for high sharpness edge holding

-S30V will have a higher toughness (25-28 ft.lbs vs 19 ft.lbs) and a much higher grindability in case damage has to be repaired, advantage to S30V

-S30V has a higher corrosion resistance (S30V shows a much higher tolerance to salt solution as compared to 440C but S90V can just equal it), advantage to S30V

-S90V has a higher abrasive wear resistance, as noted in the above that is about a 40% better CATRA score, advantage to S90V for cutting abrasive materials at a lot sharpness (CATRA stops when the blades are really dull)

Now the only advantage to S90V is in that one area and it is about 40% when tested on a machine which severely limits a number of factors some of which are actually superior in S30V (lateral loading on the edge, S30V would handle that better, again lower carbide volume).

Could a person see this difference - yes, but they would have to be doing controlled cutting and measuring sharpness and :

-the edges would need to be of a very similar angle

-same grit finish

-same initial sharpness

-consistent material

-consistent cutting (force, speed, etc.)

If any of those were not true then the performance of the blades could simply be dominated by that factor alone, i.e, if the S30V blade had a lower edge angle and/or a lower edge grit finish it would outlast the S90V blade anyway even if all of the assumptions are true (it would CATRA outlast it I mean, not just by hand).

To be very specific, if you gave me two of the blades, and one of them CATRA'ed 40% more than another could I tell them apart by hand. I am confident I could as long as I :

-had enough material to do a large sample cutting

-could measure the sharpness to at least 5% precision

-could do at least 3-5 runs to get an average

Note blunting is NONlinear, this means that if you cut to a low sharpness and were to double amount of material cut it could change the extent of dulling by as little as 2%. Just think about what that means when trying to compare blades - it is very difficult.



Just look how slowly the performance is changing at the 125 m mark. At this point the blades are at 5% of sharpness but they are changing so slowly I could double the material and barely see any difference. That means in order to determine how much material they can cut to a factor difference of 100% I need to be able to measure sharpness to a precision of 1%.

That isn't easy.

(I was going to run this out to 1000 m, just because I thought it would be amusing to cut a km of cardboard, but the problem was that I need a sample pool which is 10X larger, which means I need 250 KM of cardboard (I do ten runs with each blade) which I quickly figured out would fill my basement, thus I kept it down to about 0.1 KM).

[chuck_roxas45]

Ok, thanks, I think I understood. :D

[Henry - get both]

I first commented on this thread as a means of damage control. Its amazing how willingly people believe what they read on the internet...

Cliff isnt "wrong". He's just irresponsible to put numbers out like "an S30V dice goes from 4 to 16
and an S90V dice goes from 6 to 22". I don't think he appreciates the consistency of spydercos HT. The dice would look more like this: an S30V dice goes from 5.5 to 6 and an S90V dice goes from 9 to 10.

I raised the question "at what hardnesses are s90v and s30v equal" and Cliff asked "equal how"... Well obviously I'm talking about edge retention.... So then he says edge retention depends on XYZ... He keeps raising irrelevant points... I think the average reader here only really cares about which steel holds a working edge longer at your average 15 degree per side sharpening and at your average rockwell while cutting GENERAL STUFF. s90v will place ahead of s30v (FOR ALL PRACTICAL PURPOSES - not just when cutting highly abrasive material)

[Cliff Stamp]

Cliff isnt "wrong". He's just irresponsible to put numbers out like "an S30V dice goes from 4 to 16
and an S90V dice goes from 6 to 22".

The numbers I posted are based on actual data, they are not arbitrary, and the data was sourced in the above.

[Fancier]

I wish I could remember where I heard this, but I'm quoting somebody when I say, "You can choose your own opinions, but you cannot choose your own facts."
The concept seems particularly relevant in this thread which has touched upon the placebo effect.

[dbcad]

I first commented on this thread as a means of damage control. Its amazing how willingly people believe what they read on the internet...

Cliff isnt "wrong". He's just irresponsible to put numbers out like "an S30V dice goes from 4 to 16
and an S90V dice goes from 6 to 22". I don't think he appreciates the consistency of spydercos HT. The dice would look more like this: an S30V dice goes from 5.5 to 6 and an S90V dice goes from 9 to 10.

I raised the question "at what hardnesses are s90v and s30v equal" and Cliff asked "equal how"... Well obviously I'm talking about edge retention.... So then he says edge retention depends on XYZ... He keeps raising irrelevant points... I think the average reader here only really cares about which steel holds a working edge longer at your average 15 degree per side sharpening and at your average rockwell while cutting GENERAL STUFF. s90v will place ahead of s30v (FOR ALL PRACTICAL PURPOSES - not just when cutting highly abrasive material)

To get an answer to a technical question as vague and unspecific as what is asked would require a bit more IHMO engineering /technical / practical /scientific experience in the asking :)

When dealing with specifics of materials in the real world questions do not always have simple non technical answers. To get an accurate answer oftentimes require the skills to understand them :)

[dj moonbat]

I raised the question "at what hardnesses are s90v and s30v equal" and Cliff asked "equal how"... Well obviously I'm talking about edge retention.... So then he says edge retention depends on XYZ... He keeps raising irrelevant points... I think the average reader here only really cares about which steel holds a working edge longer at your average 15 degree per side sharpening and at your average rockwell while cutting GENERAL STUFF. s90v will place ahead of s30v (FOR ALL PRACTICAL PURPOSES - not just when cutting highly abrasive material)

I think Cliff brought up some practical purposes where S30V could be expected to (at least) match S90V:

S30V has superior edge retention than S90V if you are talking about a high push cutting sharpness at low edge angles, and is also inherently tougher so in harder work it will resist edge damage better as it can be made harder at the same toughness.

Similarly, there are "lesser" steels than S30V which are nonetheless tougher, and which do better at lower edge angles -- for the same reasons that S30V might hold an advantage over S90V in these areas. Big carbide chunks in your steel are going to affect its areas of excellence.

[Henry - get both]

The numbers I posted are based on actual data, they are not arbitrary, and the data was sourced in the above.

Wooops i misread the dice analogy... I thought you were saying that the performance overlap was because of heat treat and not because of testing limitations. Sorry.

[Henry - get both]

I think Cliff brought up some practical purposes where S30V could be expected to (at least) match S90V:



Similarly, there are "lesser" steels than S30V which are nonetheless tougher, and which do better at lower edge angles -- for the same reasons that S30V might hold an advantage over S90V in these areas. Big carbide chunks in your steel are going to affect its areas of excellence.

I understand all this.

All im trying to say is for all practical purposes (ie 30 degree edge para military 2) s90v will have (but not necessarily show...) superior edge retention...

[Cliff Stamp]

Similarly, there are "lesser" steels than S30V which are nonetheless tougher, and which do better at lower edge angles -- for the same reasons that S30V might hold an advantage over S90V in these areas. Big carbide chunks in your steel are going to affect its areas of excellence.

Roman Landes has done a lot of work in this area, it was the subject of his PhD thesis which he later turned into a book. It was never translated, but still the graphs, micro-structures, tables, etc. are easily understood.

I have discussed with Roman a collaboration with Spyderco for some time it would be an interesting thing to see if they could come together on an AEB-L line of kitchen knives or something like S1 in a larger outdoor knife.

If you are even a little interested in understanding about steels and cutting edges it is worth some time to read some of what Roman has wrote even if it is to get some perspective as what he can achieve is pretty radical.

This is from Roman :

"0,02 of an inch (0,5) is rather thick for a chopper"

To put that in perspective that is the thickness of the edges on the ABS competition knives and Roman regards that as thick at the edge. But again, that is what he did his PhD work on maximizing the ability of steel to hold a very thin geometry and a very high level of sharpness.

This is also Roman :

"My kichen knives i grind between 0,1 and 0,2 mm (tested 1mm behind the edge)an angle of 18-25°total for a chopper i use a S1 modified (0.8 Carbon) and i go to 0.2-0,25mm and an angle of 20-25°total and it still breaks bones wo chips."

Those numbers are extreme, I don't even think that is enough to describe it.

[dbcad]

Thanks Cliff :) I still have a bit of digesting on edges to do, Roman must like to cut and cook :) as well as making thin edges, Thanks for the reference. Your points for me are well taken :)

[mcjhrobinson]

i think cliff brings up great points. one of them being there is no SUPER steel. it really all depends. I have a s30v and a s35vn blade. I CANT tell the difference slicing cardboard nor paper and really i dont use my knives for such tasks. im hoping to get a pm2 in m390 in jan. just buy a spyderco and be happy! :)

[Blerv]

When something serves no current purpose it becomes archaic and is phased out. With many old steels still in mass production it does make you think. Perhaps in our niche world they have lost the luster but they are still kicking for a reason.

My mind is still spinning from this thread. Thanks to all the senior members for the discussion. :) . I'll still make baby noises at snobby sprints but won't turn up my nose as quickly for the standard model.

[chuck_roxas45]

Hhhmm, so what does all this mean in effect? Say I buy an S30V Para and an S90V para, what are the chances of my S30V holding an edge longer than the S90V if I just cut rope?

Hehehe, I know, I know...it depends. :D

But really, what are the chances? Assuming the guy who uses them can tell.

[Ankerson]

Hhhmm, so what does all this mean in effect? Say I buy an S30V Para and an S90V para, what are the chances of my S30V holding an edge longer than the S90V if I just cut rope?

Hehehe, I know, I know...it depends. :D

But really, what are the chances? Assuming the guy who uses them can tell.

From my testing, comparing those knives S90V is 60% better than S30V on Manila rope.

That's the same model knives, sharpened the same way, same edge geometry, angles etc.

That's S90V and S30V both at 60 HRC.

[chuck_roxas45]

From my testing, comparing those knives S90V is 60% better than S30V on Manila rope.

That's the same model knives, sharpened the same way, same edge geometry, angles etc.

That's S90V and S30V both at 60 HRC.

Ah thanks for the reply Jim and thanks for the testing that you do.

From what I gathered in this thread though(I'm probably wrong about that), Cliff seems to be saying that there is a large statistical chance that if I get an s90v knife, it will perform less in edge holding than the same knife with s30v. I am really wondering what kind of chances I have of getting that s90v knife that will perform less than the same knife in s30v.

I dunno if there is a possible quantified answer to this question. Something like, a 1 in 10 chance or a 1 in 500 chance, etc. It would be nice if we could get an answer that clear cut to a very complicated question.

[dbcad]

Ah thanks for the reply Jim and thanks for the testing that you do.

From what I gathered in this thread though(I'm probably wrong about that), Cliff seems to be saying that there is a large statistical chance that if I get an s90v knife, it will perform less in edge holding than the same knife with s30v. I am really wondering what kind of chances I have of getting that s90v knife that will perform less than the same knife in s30v.

I dunno if there is a possible quantified answer to this question. Something like, a 1 in 10 chance or a 1 in 500 chance, etc. It would be nice if we could get an answer that clear cut to a very complicated question.

I'm no expert :o Statistically anything is possible. I have a feeling that if you order S90V the chances are pretty overwhelming that you will get the properties you expect. Placebo can be good :D :rolleyes: :cool: :eek: :p

Sometimes it is more enjoyable to put the heavy analysis aside :)

If I ordered an S90V blade I would expect it to keep an edge for a long time......then again so does S30V....how deep does the rabbit hole go

Enjoy :)

[chuck_roxas45]

I'm no expert :o Statistically anything is possible. I have a feeling that if you order S90V the chances are pretty overwhelming that you will get the properties you expect. Placebo can be good :D :rolleyes: :cool:

Sometimes it is more enjoyable to put the heavy analysis aside :)

If I ordered an S90V blade I would expect it to keep an edge for a long time......then again so does S30V....how deep does the rabbit hole go



Enjoy :)

All the way to wonderland.

[Ankerson]

Ah thanks for the reply Jim and thanks for the testing that you do.

From what I gathered in this thread though(I'm probably wrong about that), Cliff seems to be saying that there is a large statistical chance that if I get an s90v knife, it will perform less in edge holding than the same knife with s30v. I am really wondering what kind of chances I have of getting that s90v knife that will perform less than the same knife in s30v.

I dunno if there is a possible quantified answer to this question. Something like, a 1 in 10 chance or a 1 in 500 chance, etc. It would be nice if we could get an answer that clear cut to a very complicated question.

I wouldn't worry all that much over it. :D

Life is complicated enough to worry about things that aren't likely to happen and to over complicate things just because....

Kinda like I could win the lottery, but I am not going to count on it and start spending the money......