What does blade toughness really mean?

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jsarche

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Jul 28, 2012
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I'm in the market for a new fixed blade and have been doing my due diligence on steel types but haven't been able to come up with an answer to this question: What does steel toughness mean in practical terms? I've seen lots of graphs and tables comparing the relative toughness of various types of steel, but nothing to tell me what those numbers or bar graphs really mean in the real world.

Here's an example of my confusion. Some tables and graphs I've seen say CPM 3V can be up to three or four times as tough as CPM 154, for example, depending on the heat treating. Does that mean batonning or other striking-type tasks should be avoided - or done only very lightly - with CPM 154? Does it mean I could confidently cut copper wire or other softer metals with a 3V blade? I'd love to hear about some practical translations of these toughness comparisons.

I've watched what seems like a gajillion YouTube videos showing a wide range of steel types being tested doing tasks like those and it helps, but I want a knife that will last me for many years and still be able to take anything I can throw at it.

For the record, I'm torn between a Benchmade Bushcrafter 162 and a Survive!Knives GSO 4.7 -- if it's ever available again in CPM 3V. The GSO is available right now in CPM 154, but those relative toughness charts have kind of turned me off of CPM 154. I don't worry about corrosion resistance because I live in a semi-arid climate and take good care of my gear. I would expect to be doing some general bushcraft-type activities with the knife, including batonning.

I tried searching this forum and others for answers to questions like this, but have had no luck, so I apologize if I'm not using the right search terms and missing a whole bunch of conversations.

Thanks for reading.
 
Toughness becomes more important with size. On a smaller knife, toughness is not as critical. How much batoning can you do with a 4.5" blade? not much. Same goes for chopping. So either steel will work in that case.

But to answer your question. Toughness measured is for a square steel sample with either a c-notch or a v-notch cut into it. A hammer looking arm hits the sample causing fracture. The force of that fracture is measured and that gives the steels resistance to the fracture or toughness. There are many ways to overcome lack of toughness. Blade, geometry, edge geometry, lowering hardness etc. All these can make the perceived toughness very high. So 154cm isn't as tough as 3V but with the right geometry and hardness it can be tough enough for most tasks you will need it to do and it has better corrosion resistance.
 
For given same dimension; projectile; etc...

The tougher (among test armor plates) - has lower depth of impact damage from multiple projectiles. Same as - able to withstand more shots (say in a same spot) before armor failed.

If plate material is hard but brittle = premature crack/failed. Soft & ductile = deep hole. So ideally, you want a hard material resists projectile penetration to minimize depth. And has high impact load (per volume) to minimize width (crater diameter).

Between CPM154 & Zwear which one is tougher in charpy-C test? Answer seem obvious because impact test data. I used Zwear to give better parity for both steels have carbon about 1.05%.

Look at Charpy-C at 60rc
http://www.bladeforums.com/forums/s...Notch-Values?highlight=charpy+notch+toughness

*** so a blade - given same: dimension; geometry; forces - compressive & lateral; so on
A tougher blade will suffer less damage when forces exceed impact load. Naturally when forces exceed for one blade but not the other, then one clearly is tougher than the other.
 
Knife wise it means it does not chip easily
But
is hard eough to not get dull too quick, fold over or ding.
Obviously toughmeans it won't snap off if you lever with it but my Opinel no 12 at a whopping $17 can easily claim that.
I took one to faileur once just to test it. I had to deeply notch and even then it took many cycles of bending the blade WAY over while gripped in a vise.

I think the main toughness in a knife is resistance to chipping while being hard.
Avoid ZDP-189 for tough
Yet for everything else it is one of my favorite steels.
I like 3V
No experience with 154
 
The Charpy V-notch test defines, quantifies and measures a metal's "toughness" in a very narrow sense for manufacturing and engineering purposes in order to get a consistent product, but real toughness is difficult to evaluate without some rough testing!
 
Toughness is malleability or ability to withstand impact/excessive force - a rubber band can stretch and stretch or be beaten with a hammer to extremes without breaking.
Strength is hardness - a diamond is extremely hard, but brittle and will shatter.

Toughness is important for knives you want to baton, chop, or pry with. "good" examples are 3v, infi, s7, 1075, 1095, d2. Of course this all comes down to heat treatment and blade geometry. If the steel is not properly heat treated for the intended application, its pretty useless. Same for geometry.
 
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Yup, can't delineate one vs multiple impacts toughness with Charpy tests. Ferrite allows more plastic/displacement before hit strain limits, while work hardening (RA slip then convert to Mart) capacity depend on reservoir & conversion rate.
Mecha said:
The Charpy V-notch test defines, quantifies and measures a metal's "toughness" in a very narrow sense for manufacturing and engineering purposes in order to get a consistent product, but real toughness is difficult to evaluate without some rough testing!
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Thank you all for your input. How about if I phrase it a little differently: are there certain tasks you just wouldn't tackle with certain steels? For example, would you avoid batonning or chopping with a particular steel, all other things like geometry and heat treatment being equal?
 
If a knife is used (actually used) for chopping, it is likely to get dinged. Sometimes there are foreign materials in wood. Sometimes there are knots. Sometimes you just miss or mishit. Then, you probably want the steel that only deforms and is easier to fix = easier to abrade.

Those small knives mentioned by brother Cobalt are less likely to present those issues - but not wholly impossible. Lateral loading when just slicing wood could cause edge damage (as contrasted to abrasion wear), and then you might want a steel that is easier to fix.

If the knife is to throw, then toughness is all. :eek: (Notice in that video that when he is done damaging the Ka-Bar, he literally throws it aside.)
 
bluntcut said:
Yup, can't delineate one vs multiple impacts toughness with Charpy tests. Ferrite allows more plastic/displacement before hit strain limits, while work hardening (RA slip then convert to Mart) capacity depend on reservoir & conversion rate.
Click to expand...

Not only that but the test samples are not triangular at all so they are not the same as a blade shape. Thus, it is not a complete indicator of toughness for knife shapes
 
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jsarche said:
Thank you all for your input. How about if I phrase it a little differently: are there certain tasks you just wouldn't tackle with certain steels? For example, would you avoid batonning or chopping with a particular steel, all other things like geometry and heat treatment being equal?
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Definitely. There are hundreds of different steels. I would only chop/baton with a certain handful of steels. Most are High carbon and tool steels. Mainly avoiding most "stainless super-steels" found in many popular folders, while they are some of the best in terms of edge retention, they are typically very hard and too brittle for such task as chopping/batoning/prying.
 
A2 is a good compromise between toughness and wear resistance. I usually buy 3x the A2 compared to D2 and S7.
 
Toughness to me is impact resistance, or how a steel behaves on impact; whether nothing happens, it chips, or it folds.

I could be wrong, but that's how I look at it.
 
are there certain tasks you just wouldn't tackle with certain steels?
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I'm not a go out and cut the forest down with my sheath knife kind of guy. I have learned the hard way not to cut wire ties with my ZDP-189 blades. Can chip them slightly. I cut wire ties every day. I now carry some super small diagonal cutters and just use them. Easier to get into place anyway; less chance of damaging some of the equipment.

As Charlie Mike found I have never seen A-2 chip and I have really used it hard on very hard wood but in a clean controlled environment (no rocks) not out in the woods.

Here is Team ZDP-189 with the diagonal cutters that ride in the pouch. The tiniest dikes that I could find.
The ZDP guys aren't so tough but they are smart and sharp. Wouldn't trade 'em for anything. In fact I traded my S110V to get the big one (Endura 4).

 
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RE: "I'm torn between a Benchmade Bushcrafter 162 and a Survive!Knives GSO 4.7 ...
I don't worry about corrosion resistance because I live in a semi-arid climate and take good care of my gear. I would expect to be doing some general bushcraft-type activities with the knife, including batonning."

jsarche,

A few thoughts of top of my head. I have always thought the 162 would make a great woods knife (confused about the choice of steel though), but have never been closer than handling in the store.

I would suggest you get both those two knives in hand. In my mind the handle geometry is significantly different (then again I am kind anal about how things fit my hand). The Bushcrafter in my mind has a lot of extra material (broad/blocky). I would be fine with this, but would take it to the grinder to fit my hand (better to have too much, than too little, material). I believe the ergonomics of the handle, and the feel in hand will speak volumes on personal selection between these two options.

Blade steel wise, probably not as important as the grind geometry of the blade (which can be modified to some extent based on intended use). Reading over your posts ..., it would be my assumption the GSO in 3V would be preferable, provided the handle fits your hand. My GSO 4.1 3V is a bit small in overall circumference for the type of things I got it for, and as result stays home more often than I would otherwise like (I believe the 4.7 is a bit taller profile though). Far as I remember the 162 is/was only available in S30V. Not typically a steel choice for batoning, etc., vs. 3V somewhat a specialty. I think 1095 with a good heat treat is more than sufficient and is easy to maintain (for the things you have mentioned).

Sheath options (factory sheaths) may also be significant factor for you (how you plan to carry, maintenance, etc). The original 162 had a fairly decent leather sheath (somewhat traditional). I believe newer versions have kydex option. After some time, you may consider having a sheath built specific to your useage wants, but it will most likely take a little time to develop those interests based on first hand use.

162 handle scales I believe are fixed (hollow rivet type construction). Means changing the scales is more difficult. Open rivets however allow cordage pass-thru for attaching to a pole, etc. GSO handles are much more easily removeable/exchangeable using a screw together construction (unless they have changed design ...). One could argue, removable handle scales would allow for making for better pole attachment options (spear).
 
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How would we rate S35V on the toughness scale? I have a fixie made out of it. My other fixie is 02 steel.
 
Thank you for the excellent suggestions. Spey, I've handled the Benchmade at a store, but I don't know anybody who owns a GSO, so I'd be taking a bit of a chance. The Benchmade felt OK - not a perfect fit for me but I feel like it would be just fine after a while. Also, I have to admit a tiny bit of discomfort with the fixed scales on the Benchmade, for exactly the reasons you mention.
 
The BM162 is a tough knife
I have batoned and done light chopping no problem

The GSO 4.7 is great as well
I highly doubt you could easily break any of these knives
 
jsarche said:
Thank you for the excellent suggestions. Spey, I've handled the Benchmade at a store, but I don't know anybody who owns a GSO, so I'd be taking a bit of a chance. The Benchmade felt OK - not a perfect fit for me but I feel like it would be just fine after a while. Also, I have to admit a tiny bit of discomfort with the fixed scales on the Benchmade, for exactly the reasons you mention.
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jsarche,
If you get your hands on a GSO and don't like it, they re-sell pretty easily for little/no loss. You can sometimes get them off the BF exchange, otherwise they list some on their website once in awhile (not too often). Best deal on a 4.7 is to snag an "ugly betty" here, but you need to be aware of when they post any available, as they sell out rather fast: http://surviveknives.com/gso-4-7-ugly-betty/
The 4.7 is bigger than the BM162, you might prefer to wait and get one of the revised GSO-4.1s that are coming out soon... I wouldn't bet on them being available until the new year, but they may list some "ugly betty" and "factory seconds" as they push their pre-ordered knives to completion, that's what usually happens anyway. The 4.1s are made with Delta-3V that you might find of compelling interest...

Regarding "toughness" of these knives, I haven't handled the Benchmade but have (ab)used a number of GSOs in 3V, Cruforge V, M390, and CPM-20CV. I've thrown them repeatedly as well as batonned both wood and steel (metal roofing, gutters) with these knives, as well as re-sharpened them. My advice for toughness would be to pick 3V or CruV if you plan on hacking your way through sheet metal or want to keep the edge hair-splitting sharp, but all of the knives in their respective steels handled throwing just fine.

Example:
[video=youtube;F-7qPjJd5xo]https://www.youtube.com/watch?v=F-7qPjJd5xo[/video]


Something else you might consider: a few of those posting in your thread are small-time knifemakers and may be able to build you exactly the knife you are looking for at a price that will compete with those two production-models. For example:

From bluntcut
http://www.bladeforums.com/forums/showthread.php/1443441-Aebl-W2-1095-knives

From Charlie Mike:
http://www.bladeforums.com/forums/showthread.php/1387970-Damascus-combat-set
 
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