SOG X-42 steel!

[Sergiusz Mitin]

Well, Cliff,
Probably I have formulated my thoughts not too completely asking half-question and – naturally - receiving half-answer
The highest impact resistance (an ability to resist fracture) will display the softest steel, something like 420J2 at 54-56 HRC or, say, AUS-6 at 55-57. On the other hand they are not too tough (tensile strength? – oh, my poor English!) and will display extensive edge rolling on somewhat heavier cutting. Even on non-abrasive materials like wood. On abrasive materials like rope or cardboard the edge would display pretty mediocre performance being extensively rolled and worn out at the same time.

The other end of the scale – BG-42 or ATS-34 at appr. 60 HRC – great edge hold on pure cutting (high abrasion resistance) but could chip easily even on light-medium impacts and the blade can be broken easily on light prying (not good situation in wilderness).

So 440C, VG-10 (at 58-59 HRC) or at least AUS-8 (at 57-58) could be considered as well balanced between resistance against edge rolling on one side and chipping on another in real life use and taken as optimal stainless steels for general purpose outdoors knife blades, right?

Probably some tool steels like M-2 or D-2 or some spring steels like 5160 being properly heat treated could display even better balance in these properties. However I’m artificially narrowing the discussion to stainless steels only, mostly for maintenance reasons...

Any candidates more among stainless steels?

 

[Cliff Stamp]

Sergiusz Mitin :

[AISI 420 / 54-56 HRC, AUS-6 / 55-57]

... will display extensive edge rolling on somewhat heavier cutting. Even on non-abrasive materials like wood.

Yes they are weaker and yes this will cause them to roll under a lower stress, or roll more under the same load, however the difference of a few RC, while enough to notice on precision cutting, is not enough to induce "extensive" edge rolling, where little was seen before. Tensile strength is correlated in a linear manner with HRC. However fracture toughness is not.

On abrasive materials like rope or cardboard the edge would display pretty mediocre performance being extensively rolled and worn out at the same time.

It is not the steel I would chose for that type of work, for that reason, as yes the edge holding will be lower because of the softer steel, however due to the higher toughness and the critical nature of this with chopping, you could counteract this with a geometrical optomization of the edge profile. Getting specific, you can go much thinner with a tougher steel as it can handle the accidental high stress impacts without gross damage, and this will greatly extended the lifetime of the cutting ability compared to a thicker edge on a more brittle steel.

So 440C, VG-10 (at 58-59 HRC) or at least AUS-8 (at 57-58) could be considered as well balanced between resistance against edge rolling on one side and chipping on another in real life use and taken as optimal stainless steels for general purpose outdoors knife blades, right?

Edge holding of this degree is very important I will agree when you want to be able to cut very flismy materials such as light papers, plastics, foods like tomatoes, and flesh and thus for a general purpose outdoors blade which combines these activities with heavy chopping a high hardness can be of benefit as for example if you want to prepare a fillet or whatever after doing extended wood chopping. The higher hardness also allows you to go with a thinner geometry (assuming the fracture toughness is enough) at a given stress level as the resistance to rolling is greater.

However, in my experience these steels are simply too prone to extensive chipping and/or gross failure to counteract the small advantage of greater edge holding due to resistance to rolling. This is however greatly dependent on the type of wood you are cutting, how much of it you do, the amount of force you use, the amount of skill you have and your enviroment (cold). If you were doing for example very little chopping or other high stress work, and mainly precision work, then you would a blade optomized more for that profile and thus the extra few RC points would indeed be appreciated. You could also for example, just be willing to chop at for example half strength, depending on how little of it you had to do, and be very careful to avoid knots and inclusions.

For a general outdoors blade, I would much rather in fact use a simple blade like the Jungle knife or Golok from Martindale, which has a very low RC, ~45 or so than a high alloy stainless machete. The Golok, while rather soft, is enough to last for a day of limbing and such, and be able to cut light vegetation at the end, and there is no danger of gross fracture, and any edge impact just produces deformation. It is of course possible to get ~60 RC with a tool steel and not be concerned about fracture, but for stainless steels I would go much softer.

-Cliff

 

[frank k]

Serg,

I think I understand what you are thinking – steels such as AUS8 and VG10 that are not too soft nor too hard, make excellent all around stainless steels. I would agree to a point, but I believe, in general that it is better to match the steel to the design of the knife, the user and the expected use.

For knives used for light or medium duty cutting (no prying or chopping), even thin edged stainless steels will generally hold up well. I have been using a thin edged stainless Opinel for just about everything in the kitchen and around the house lately and I have not had a problem with edge roll. I normally don’t have much of a problem with edge roll with other thin edged stainless blades including SAKs and paring knives. I sometimes get very small chips with my thin edged EDC folders with premium grade stainless blades (ATS34/154CM and VG10 mostly). I still generally prefer the premium steels, since they hold an edge longer and the tiny chips don’t bother me. In heavier use, I would expect to see greater chipping with the premium steels and some edge roll (or a combination of roll and chipping) with the softer stainless steels.

For a blade intended to stand up to much chopping, heavy use and abuse, I want a lot of toughness (impact strength), so that I can minimize damage while keeping a thin edge for high performance. Stainless knife steels are not very tough in general, for this reason I would prefer a tougher non stainless steel. A medium carbon steel, as Cliff suggested, will get the job done and the tougher tool steels* are even better, since you can run them hard (for less edge roll) and they have better wear resistance.

Generally, stainless cutlery steels are tougher at low hardness levels - if I were limited to stainless steel for a chopping knife, I would not want one which was too hard.

Too boil all this down, I prefer harder grades of stainless steels for light cutting and a tough carbon steels for heavy chopping. The softer stainless steels are a good choice when a combination of decent durability and rust resistance is needed - but I would prefer a tougher steel for a dedicated chopping blade.


- Frank






* Edit - To be clear, I mean tool steels with fairly high impact resistance such as L6, CPM3V and A9.

 

[Sergiusz Mitin]

Thanks Cliff,
Thanks Frank!

I think about medium sized (up to 5-inches) outdoors fixed blade for light to medium cutting tasks (supported with axe for heavier chores). Obligatorily stainless for maintenance reasons. At the same time able to oppose occasional, mostly accidental abuse without (or with minimal) damage.

Seems AUS-8, 440C or at least VG-10 would be better choice than ATS-34/154CM or BG-42...

 

[frank k]

Originally posted by Sergiusz Mitin
Seems AUS-8, 440C or at least VG-10 would be better choice than ATS-34/154CM or BG-42...

Serg, It depends on how the blade is used. My uses for a under 5” camp knife include camp food prep, light to medium duty utility, and cleaning fish and game. I guess I am not particularly hard on such knives since, I don’t abuse them and leave the chopping to an axe. For this reason, of the steels you mentioned (AUS8, 440C, VG10, ATS34/154CM, & BG42), I would prefer BG42 or VG10 (toss up), if I thought I needed more durability for harder use, I would choose AUS8.



-Frank.

 

[Sergiusz Mitin]

Frank,

My uses for a under 5” camp knife include camp food prep, light to medium duty utility, and cleaning fish and game. I guess I am not particularly hard on such knives since, I don’t abuse them and leave the chopping to an axe

Exactly what I would do also. My intention to go with somewhat less brittle steel is based on desire to prevent chipping or blade breaking on accidental abuse. Or maybe somewhat exaggerated fear to break or badly damage the blade when it can’t be replaced. Something like kind of 100% reliability desire...

Looking from reliability standpoint and, btw, returning to this thread original subject – can you consider BG-42 at about 60 HRC right choice for so large blade as SOG X-42 Field Knife? of course taking into consideration its general design, shape, balance and intended use...

 

[frank k]

Originally posted by Sergiusz Mitin
Looking from reliability standpoint and, btw, returning to this thread original subject – can you consider BG-42 at about 60 HRC right choice for so large blade as SOG X-42 Field Knife? of course taking into consideration its general design, shape, balance and intended use...

Serg, Based on the appearance of the Field knife only (I do not own one), for the type of use we are discussing (civilian camp knife), I would say yes. The advantage of BG42 (and other premium stainless steels) is their combination of excellent edge holding and decent rust resistance – which add up to low maintenance. Durability can be a problem, but you have to decide how critical durability is verses edge holding and corrosion resistance. For most civilian outdoor activities, a damaged or even broken knife is little more than a inconvenience, after all you most likely could still use a damaged knife, even if you did not have a spare knife of some sort - rarely is it a matter of life and death.

If the same design were intended for military use, long term survival or deep wilderness travel, where a blade failure is potentially much more critical, I would choose a tougher non stainless steel (something like A2, 52100/SR101 or 50100/Carbon V/0170-6C sould do nicely and something like CMP3V sould be about optimal). I might also consider (depending on the steel) going to a slightly thicker edge to trade some cutting performance for durability for such use. If for some reason I was confined to a stainless steel, I would want a soft one, for durability.


- Frank

 

[Sergiusz Mitin]

A lot to think about...
Thanks!

 

[Cliff Stamp]

Sergiusz Mitin :

... consider BG-42 at about 60 HRC right choice for so large blade as SOG X-42 Field Knife?

If I was using BG-42 I would be running it harder, at that hardness it has little advantage over ATS-34 in regards to edge holding, or potential cutting ability. That being said, there would be no problems with durability unless you attempted to chop heavy bone, or did heavy assisted chopping or splitting (use a heavy mallet on the spine). I have used very brittle steels at high hardness levels (CPM-10V 62-63 RC, D2 at 62 RC), for all manner of cutting, and chipping is minimal as long as you take care in use, and mainly have a secondary blade for any heavier use.

For that type of cutting though, the Deerhunter from A. G. Russell would be directly superior offering a very large increase in cutting ability, many times to one, with the only advantage of the X42 being the slightly longer blade, and extra prying strength. The latter I would not recommend actually be used because prying with a 60 RC stainless steel is asking for trouble, there is little or no flex before gross failure. Now if the X42 had an edge profile similar to the Deerhunter, with a ~64 RC BG-42 edge, then it would have a significant advantage in edge holding, and a greater potential for cutting ability.

-Cliff

 

[Sergiusz Mitin]

Thanks Cliff.
I do not have personal experience with A.G. Russell Deer Hunter. However my understanding suggests me that with 100 mm long and 2 mm thick blade it is rather not intended for any kind of chopping, prying or pounding. Certainly this is not general-purpose camping knife. I would reserve such blade for pure cutting and I guess A.G. have intended the same. So some additional edge retention on pure cutting on abrasive materials (deer’s belly sometimes can be pretty gritty and abrasive) can be bought at the cost of some lose of tensile strength by all means.

Just for comparison – A.G. Russell 6,5-inched blade of Camp Knife is made of AUS-8 at 57-59 HRC.

SOG X-42 Field Knife is intended for basically another kind of use than Deer Hunter – exactly as general purpose camping knife. So this might cause going with lower RC to add some blade strength and reliability against accidental chipping...

 

[frank k]

Serg & Cliff,

Do you know what the edge thickness of the Field knife is?

Cliff,


A BG42/Rc 64 Deer Hunter would certainly make a high performance cutter due to the thin edge (about the same as a SAK behind the bevel) and the resistance to wear and edge roll provided by BG42 at Rc 64, but it would be something I would be careful not to abuse. It seems that most factories have lowered the hardness levels of the premium stainless steels a bit from those of a few years ago – I would guess this is because they had a lot of customers who damaged their blades. Of course if you don’t over stress them, the higher hardness blades would be preferable – this gets back to the durability verses performance issue, optimally, you want to trade just enough performance for the durability you need.



-Frank

 

[Sergiusz Mitin]

Frank,
The edge thickness (just behind sharpening area) is different:
1,0 mm at the tip
0,6 mm at the belly and front part of recurve
0,5 mm at the rear part of recurve up to the choil (measured with 0,1-mm accurate caliper)
This seems somewhat strange because the wideness of fully flat grind at the belly and at the back of the edge is exactly the same...
Designing such knife I would go rather with slightly thicker edge at the back side (to apply more force for heavy cutting) and thinner edge at the belly for fine work. This result could be obtained if they would taper the stock slightly in tip direction.
I would also reduce the choil at least at half – it “eats” pretty decent part of valuable edge length, however I do not see what sensible it is intended for.
The blade cuts nicely.
As to handling comfort and balance – very nice, it is really good for both heavy and precise cutting, I have tried mine in kitchen and backyard pretty extensively. The pattern on thumb ramp might be somewhat less aggressive, this is easy to correct in home conditions.
Some pictures added:

In my opinion it is pretty decent field/camping/general-utility knife. Btw, the biggest knife I can do something sensibly accurate and the heaviest piece I agree to carry in my laziness

 

[frank k]

Thanks Serg,

.5-.6 mm is about what I would expect for a factory knife like the Field Knife – thin (certainly thinner than many) but not super thin. That is about the same as or slightly less than my Moran drop point (.025”/.6 mm with an included edge angle of about 29 degrees) and about double the thickness of a Deer Hunter or a SAK.


-Frank

 

[Sergiusz Mitin]

Wow, Frank! What is with your Moran? Both my knives (drop point and upswept point) have 0,4-mm thick edge only at the major part and 0,5 mm at the very tip...
SAK’s are well known for their thin edges and high cutting performance, however somewhat thicker edge should be expected on general use camping knife. So the proportions of SOG Field Knife could be considered as reasonably balanced, isn’t it?

 

[frank k]

Serg,

Edges of about that thickness are very common for factory hunting knives - personally, I would prefer a bit thinner edge, maybe about .4mm/.016” or so.

I measured my Moran again and came up with .025” at the thicker parts (near the choil and tip) and .020”/.5mm at the thinnest (near the belly). I am not surprised at the difference in thickness compared to your Morans, as there seems to be a lot of variation in edge thickness, even in factory knives. Of course, variations in bevel angles will also affect the thickness behind the bevel.


- Frank.

 

[Cliff Stamp]

Sergiusz Mitin :

[Deerhunter]

However my understanding suggests me that with 100 mm long and 2 mm thick blade it is rather not intended for any kind of chopping, prying or pounding.

You can do assisted chopping with the Deerhunter, baton work, though I would watch the edge around knots as given its thickness it will ripple easily. As for the other two, neither is the Field knife or in fact any SOG knife in general. For that kind of use you want a spring steel or similar, the only way you can do that with stainless is to use a very heavy stock thickness and very thick grinds, even then you are still asking for trouble as failure will be dramatic and explosive for that type of use. The only functional advantage of the field knife over the Deerhunter would be in splitting knotty wood using a mallet, or heavy bone work.

Just for comparison A.G. Russell 6,5-inched blade of Camp Knife is made of AUS-8 at 57-59 HRC.

There are many different versions, D2, ATS-34. VG-10 etc. .

Frank :

[bg-42 ~64 RC Deerhunter]

... it would be something I would be careful not to abuse

You are losing durability, there is no argument to that, the ductility is going to be very low at max hardness, baton work would be out and you would want to be more careful around joints. I would not argue that it would be a better knife at that hardness in general, though more coherent, but for that steel it would be otherwise it is just more cost with no significant gain outside of promotional ability. If you are running it at ~59 RC just use 440C or similar. Now a 59 440C version compared to a 64 RC BG-42 one would be two similar but different knives offering two packages which would be more or less suitable depending on the user, make another out of 5160 / 3V at 58 RC to round it out completely.

-Cliff

 

[Sergiusz Mitin]

Cliff, regarding A.G. Russell Camp Knife,

There are many different versions, D2, ATS-34. VG-10 etc. .

Well, which one would you prefer?

 

[Jeff Clark]

Cliff, The lightweight AG Russell Deer Hunter comes in VG-10, AUS8A, and D2 at the moment (the ATS-34 is not in the current catalog). There are various larger AG Russell "Camp Knives" at the moment and they are all listed as AUS8A. BTW Santa brought me a D2 Deer Hunter for Christmas.

 

[frank k]

Cliff:

Originally posted by Cliff Stamp


[bg-42 ~64 RC Deerhunter]



You are losing durability, there is no argument to that, the ductility is going to be very low at max hardness, baton work would be out and you would want to be more careful around joints. I would not argue that it would be a better knife at that hardness in general, though more coherent, but for that steel it would be otherwise it is just more cost with no significant gain outside of promotional ability. If you are running it at ~59 RC just use 440C or similar. Now a 59 440C version compared to a 64 RC BG-42 one would be two similar but different knives offering two packages which would be more or less suitable depending on the user, make another out of 5160 / 3V at 58 RC to round it out completely.

Cutting joints on big game can put a lot of bending stress on a blade if you are not real careful and get the cutting angle just right - and a knife with a very thin blade and a super hard/ brittle stainless steel, is not very forgiving when over stressed.


BG42 still has an advantage of greater abrasive wear resistance compared to 440C, even at the same Rockwell hardness, much the same way 440C has an advantage when compared to 420HC. This is due to the difference in the amounts and types of carbides found in the different steels - 440C has about a 12% carbide content by volume (nearly all chromium carbides at Rc66-68), and BG42 has a total of 19% carbides (a mixture of chromium at Rc66-68, molybdenum at Rc 72-77, and vanadium carbides at Rc 82-84).


For me, I think 3V would be about ideal for something like the Deer Hunter. 3V has about the same wear and rust resistance as D2, with about 4 times the toughness – this should do away with any durability concerns – at least in normal use.



-Frank

 

[Cliff Stamp]

frank k :

BG42 still has an advantage of greater abrasive wear resistance compared to 440C ...

Yes, but this isn't a real functional advantage in regards to edge life in most cases unless you want to use knives that are really blunt. For knife use, wear resistance only comes into edge holding on cutting very abrasive materials (relative to steel which is a high demand), which is rare, and doing so for a long time. Wear resistance is one of the more overhyped steel properties and translates to very little in regards to real performance gains and is easily overshadowed by a small change in RC.

In regards to the Deerhunters, based on what I have seen with an AUS-8A, VG-10 and D2 one, I would pick the D2 as the edge holding is better, and I didn't pay for any of them so cost isn't a factor. If cost was a factor, I would probably go with the AUS-8A one if I would be leaving it at the NIB profiles, which I probably would not. I am unsure how the edges would react to low angles which would be critical. I'll have more quantitative comments after one final round of rope cutting and sharpening.

-Cliff