Toughest Kid on the Block

skmo

skmo

Joined
Feb 21, 2015
Messages
51
I've read makers and users talk about the "toughness" of various steels. I'm going to assume (yes, I know what it makes me) that this is going to refer to making a steel tougher to break in case of chopping and hitting something hard and/or chipping the edge of the blade. Some of the most common contenders include: The 10xx family: 1070, 1075, 1080, 1084, 1085, 1090, and of course, 1095. Then there's the more complex steels: 5160, 6150, 9260, 52100, and 80CRv2, There's the tool steels: W1, W2, 01, L6, A2, & D2. Last come the 'hopped up on steroids" steels: CPM-S7, Z-Wear, Z-Tuff, Cru-Wear, and CPM-3V. How are some of these going to compare to each other in toughness overall, assuming the heat treat is done by someone slightly smarter than my brother-in-law?
 
From Larrin Larrin via https://knifesteelnerds.com/2020/05/01/testing-the-edge-retention-of-48-knife-steels/

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I’m a huge fan of Larrin’s work but how can 3V at a hardness of 60 Rc have toughness values of 35 ft-lbs in one graph and 70 ft-lbs in the next graph?
 
When talking about what makes a good knife remember - toughness is only one of several things you need in a knife blade.

You have toughness, hardness, and wear resistance (a combination of sharpenability, edge retention, and other things).

My standard explanation of how these work together is a knife made from steel, glass, and rubber.
The glass knife is very hard and will get very sharp, but is not tough. It will only last one or two cuts before breaking or loosing the edge.
The rubber knife is very tough but not very hard. It will not break but won't get sharp and will bend easily.
The steel knife is able to be heat treated to get a balance of toughness, hardness, and sharpenability.

Different steels are alloyed to make one of these attributes prominent. Some shine on two of them. There is no One Steel that is superior over all others. It depends on the purpose and use of the blade on which steel you pick. If you look at the first chart you will see all the most popular carbon steels for kitchen blades at the bottom ???? Why would you pick the lowest toughness steel for a knife? ... Because it can get very hard and retain a very sharp edge for kitchen slicing. However, for a camp knife used to chop brush and dig holes in the ground, 8670 or 5160 are far better choices.
 
Larrin has posted some amazing information on many of the steels you listed, including their toughness.

Proper heat treatment and selection of the steel according to the desired task is very important, but in my opinion and experience the best steel in the world won't help you much if you don't design you blade properly and put the correct edge geometry on it for your desired task.
 
Creaky Bones said:
I’m a huge fan of Larrin’s work but how can 3V at a hardness of 60 Rc have toughness values of 35 ft-lbs in one graph and 70 ft-lbs in the next graph?
Click to expand...

Depends on the size of the test sample. Larrin’s study uses the smaller test sample size. A larger sample will take more energy to break. The comparisons are only viable if comparing the same sample size.
 
skmo said:
I've read makers and users talk about the "toughness" of various steels. I'm going to assume (yes, I know what it makes me) that this is going to refer to making a steel tougher to break in case of chopping and hitting something hard and/or chipping the edge of the blade. Some of the most common contenders include: The 10xx family: 1070, 1075, 1080, 1084, 1085, 1090, and of course, 1095. Then there's the more complex steels: 5160, 6150, 9260, 52100, and 80CRv2, There's the tool steels: W1, W2, 01, L6, A2, & D2. Last come the 'hopped up on steroids" steels: CPM-S7, Z-Wear, Z-Tuff, Cru-Wear, and CPM-3V. How are some of these going to compare to each other in toughness overall, assuming the heat treat is done by someone slightly smarter than my brother-in-law?
Click to expand...

Depending on your budget, 8670, A8mod, Z-tuff. 3v is a fine steel, but a8mod is a hell of a lot cheaper, but gives up some wear resistance, and z-tuff is a lot tougher, again giving up some wear resistance.

S7 is still not tested, nor is 9260 or 6150. Don’t forget competition choppers have been winning with M4 and V4e. I use a lot of z-wear, and have never had one returned with damage, even at Rc64.
 
Don’t forget, 8670 has a very wide acceptable heat treat range, widest of any simple steel I have tested. https://www.bladeforums.com/threads/8670-heat-treat-coupon-results.1559745/ This is the recommended best steel for a beginner with minimal equipment. I run workshop knifemaking groups through my mental health practise, and start everyone off with 8670, or reclaimed 15n20 (if they need odd sizes.)
 
Y'all have heard the phrase "Ask and ye shall receive" I presume? You gentlemen (and ladies, if any) deliver! Grandpa was a blacksmith when horseless carriages were getting popular, and he had to learn to be a mechanic. However, I remember watching him make steel things he needed around his place, lately I've been thinking about setting up a forge and trying my hand at blacksmithing, and eventually making knives in Summer when I'm not teaching. I've looked over the stickies, when I have more questions it's good to know I can get good answers here. Thanks!
 
By the way, to answer the question of what I want, the two things I have in my head currently are a large knife that's a cross between a heavy big knife and a machete. I like LT Wright's Overland Machete in 1075, but instead of 3/32 I'd like more like 5/32. Not a real chopper per se, but a little more heft for the tough scrub oak we have in our mountains here (Wasatch Front and Uintah Mountains in Utah.) I want the blade to be tough, Tough, TOUGH. I'm not as worried about edge retention, as I seem to have a gift for restoring an edge in the field.

The other blade will be a small skinner/utility knife. Owing to my Eskimo heritage (Inupiat from Point Hope, Alaska) I want am ulu shaped blade that's ALL belly but with a traditional knife handle, not an ulu handle on the back of the blade. I'm wanting to forge this, I'm leaning toward 80CRv2 because I already have a big piece of it from Aldo Bruno, 3"x48" at .250.
 
skmo said:
By the way, to answer the question of what I want, the two things I have in my head currently are a large knife that's a cross between a heavy big knife and a machete. I like LT Wright's Overland Machete in 1075, but instead of 3/32 I'd like more like 5/32. Not a real chopper per se, but a little more heft for the tough scrub oak we have in our mountains here (Wasatch Front and Uintah Mountains in Utah.) I want the blade to be tough, Tough, TOUGH. I'm not as worried about edge retention, as I seem to have a gift for restoring an edge in the field.

The other blade will be a small skinner/utility knife. Owing to my Eskimo heritage (Inupiat from Point Hope, Alaska) I want am ulu shaped blade that's ALL belly but with a traditional knife handle, not an ulu handle on the back of the blade. I'm wanting to forge this, I'm leaning toward 80CRv2 because I already have a big piece of it from Aldo Bruno, 3"x48" at .250.
Click to expand...

8670 will be perfect for the machete.
 
While I enjoy the academic aspect of discussing steel toughness as much as the next guy, it doesn't do much to relate that information to a practical personal understanding of what those numbers mean. There are lots of steels that have a reputation for being "tough," but all of Larrin's testing pretty well proves that "tough" isn't a good descriptor of some of those steels, relatively speaking. Or maybe that means that many steels are many times tougher than is practically necessary for the purposes for which we use them. Either way, if you haven't made a knife for the sole purpose of breaking it, you should. You might be surprised how difficult that 80CrV2 is to break.
 
tkroenlein said:
While I enjoy the academic aspect of discussing steel toughness as much as the next guy, it doesn't do much to relate that information to a practical personal understanding of what those numbers mean. There are lots of steels that have a reputation for being "tough," but all of Larrin's testing pretty well proves that "tough" isn't a good descriptor of some of those steels, relatively speaking. Or maybe that means that many steels are many times tougher than is practically necessary for the purposes for which we use them. Either way, if you haven't made a knife for the sole purpose of breaking it, you should. You might be surprised how difficult that 80CrV2 is to break.
Click to expand...
Since 80CrV2 is in the upper echelon of toughness according to our testing I'm not sure that's a good counterexample. But regardless, how difficult it is to break a knife will be highly dependent on the geometry of the knife. For example, a 1/4" thick knife would take quite a bit to break, especially if it's on the shorter side, even in a relatively low toughness steel. The toughness numbers are not "only academic," but they are tests of materials not knife design.
 
I most assuredly did not intend to imply that the toughness numbers were only academic. For me personally, seeing the wide range of steels compared to each other have helped me understand what to expect between steels and even small changes, like in austenitizing and tempering temperatures.

So, to be clearer, and to Larrin Larrin 's point, the toughness values are a comparison of steels to each other, but do not answer the question "how much toughness do you need?" Steels like 1095, O1 and D2 are very low in comparison to other steels, yet have been used successfully in bunches and bunches of knives. I did not suggest 80CrV2 for any other reason than the OP said he had some. I think testing (or breaking) any steel on the chart helps to build a frame of reference for the knife maker.

That's all just a long way of saying, skmo skmo , take some of that 80CrV2 and make a knife and test it to failure. Then you'll know if you need tougher steel, or you can sacrifice some of that toughness for another desirable property for the knife you want to make.
 
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