Help me understand INFI

[Twindog]

The composition of A8 mod was (is?) listed incorrectly on the AKS website. There has never been a 5% Cr A8 mod. If such a steel was tested it wouldn’t have worse toughness than A8 mod anyway.

I know nothing about it, but AKS lists Cr at 5.3 percent.

Abrams lists it even higher, more than 7 percent.

https://us.abrams-industries.com/steel/tool-steel/a8

Fishun lists it at 8 percent, but it's difficult to read. So I may be wrong.
aisi-a8-mod-cold-work-tool-steel

But, as you say, others list it much lower. Steel Data lists it at 1.3 percent.
740.html

So what's going on?

 

[fullswing]

." the lack of edge retention would make me not reach for a blade made of INFI in most cases in the field" Ive used a Hellrazor extensively in the woods and i dont see lack of edge retention; have you used that F16 alot in the field and found it dulled quickly ?

Yes. Keep in mind it's my only INFI blade. And it's really not optimized for slicing work in any way, especially the edge geometry,

But after I received it, I sharpened it up and took it on my last 4x4 adventure in the woods. Spent a few hours out and about hacking tree limbs, batoning and whatnot. Got home and tried to cut paper, but couldn't get a single good slice. It basically performed exactly the same as the knife in the video from DBK. That being said, it sharpens up very easily and is back to cutting paper with just a few minutes of work. If I didn't have a way to maintain it and was stuck out in the woods, I could imagine that feather sticking would become difficult quickly after time spent chopping.

 

[Cobalt]

The composition of A8 mod was (is?) listed incorrectly on the AKS website. There has never been a 5% Cr A8 mod. If such a steel was tested it wouldn’t have worse toughness than A8 mod anyway.

As far as I know, true. In fact Johanning was the first to use it successfully, that I recall. However, that doesn't mean that companies weren't advertising A8mod with 5% chrome and people would quote that in threads and even have arguments over it. But those arguments were in the late 90's. on old KF, and RecK. In any case, places are still erroneously listing it like they did back then causing the confusion. lol.

 

[Boru13]

My last SYKCO blade was .065" bte.

.065".

That's ridiculous.

 

[goldie]

Yes. Keep in mind it's my only INFI blade. And it's really not optimized for slicing work in any way, especially the edge geometry,

But after I received it, I sharpened it up and took it on my last 4x4 adventure in the woods. Spent a few hours out and about hacking tree limbs, batoning and whatnot. Got home and tried to cut paper, but couldn't get a single good slice. It basically performed exactly the same as the knife in the video from DBK. That being said, it sharpens up very easily and is back to cutting paper with just a few minutes of work. If I didn't have a way to maintain it and was stuck out in the woods, I could imagine that feather sticking would become difficult quickly after time spent chopping.

Interesting.After using mine i sharpened it ; i usually run for the sharpener as soon as im done,ill have to try slicing after the next time i use it and see if i have similar results.

 

[shinyedges]

That's ridiculous.

What, you don't like a lot of resistance to cutting?

 

[Blues]

What, you don't like a lot of resistance to cutting?

He gets enough resistance just being a moderator.

(Thank you, we'll be here all week. Don't forget to tip the waitresses.)

 

[shinyedges]

He gets enough resistance just being a moderator.

No one resists senpai!

 

[ace]

As far as I know, true. In fact Johanning was the first to use it successfully, that I recall. However, that doesn't mean that companies weren't advertising A8mod with 5% chrome and people would quote that in threads and even have arguments over it. But those arguments were in the late 90's. on old KF, and RecK. In any case, places are still erroneously listing it like they did back then causing the confusion. lol.

Then why keep on bringing this up and questioning Larrin's numbers if you know 5%Cr composition was a mistake? This perpetuates this error and causes even more confusion. I also don't necessarily see where A8Mod toughness is shown as close to A2, if anything it is significantly higher than A2. It is close to AEB-L though and given same geometry both steels should perform in a similar fashion with AEB-L having better corrosion resistance. AEB-L also works very well at higher hardness than A8mod is typically treated to, so in smaller thinner blades that are not expected to go through stones, but are expected to cut it should be a better choice.

 

[rodriguezryan14]

I’ve been using A8 mod quite a bit. It’s a good tough steel, and with my heat treat and edge geometry, it held a really good edge quartering and skinning an elk the other day. I was very impressed. I’m running it around 59 rc. And I did plenty of firewood splitting and batonning. I’m gonna bump it up a point or two in rc and see what it can do! I don’t like busses edge geometry, and they do run their steel a little soft usually! Other than that, it’s a great steel, but people are usually put off because they like the mystique involved more than facts I guess! Look at Larrins threads and how those went! I don’t know what the issue is with it being A8 mod anyway!! Busse makes a hell of an indestructible knife, with a great heat treat!!

 

[rodriguezryan14]

My understanding is that A8(mod) responds really well to high-end heat treating, kind of like 52100. Busse has his own heat treat down pretty well.

Here's a short video of people pounding a Nexus Centurione into a boulder without damage. The custom heat treat was elaborate.

The steel was A8(mod) at 59 Rc, with multiple thermal treatments. Part of the process was designed to prevent the participation of chromium carbides and transform residual austenite into martensites -- but I don't know specifics.

My Nexus is in this photo, just above a Busse Fat Ash, which porks out at a third of an inch thick at the spine.

However, you have to get the heat treat right. Here's a cracked blade of A8(mod) that I had custom heat treated by a specialist in Europe known for his work with A8(mod). Something went wrong, I don't know what. But it failed, showing less toughness than a replace of Vanax SuperClean with the exact same geometry.

You might want to contact Moletta. I think he was part of the heat treating of A8(mod). Done right, this steel is really good -- really tough.

Nothing super fancy about heat treating it! Maybe lower aus temps and longer soak times, multiple tempers and cryo. Nothing too special to get great performance out of it! I’ve been experimenting a lot with it lately!! And trust me, all I do is research about these things! People go on about some super fancy heat treat. But it’s the care and timing of your process that matters more, how you quench, how you cryo, soak times, a bunch or little details go into it! Just nothing overly fancy!

 

[rodriguezryan14]

So busse never makes a mistake? See it’s things like this!! There can and will always be a problem somewhere!! No one is exempt!! I had one A8 mod blade that wouldn’t harden!! I re austenitized it again at a higher temp and it still wouldn’t harden. It was the actual bar of steel! And I’ve used several from that same place. Had I not tested the rc several different times I would have never known. It was 50 rc after quench, even after cryo it never tested over 52. That’s a steel problem, not a maker issue. But issues do happen. You’re basically insinuating that busse has never and will never have an issue leave their shop! It happens

^ Thats why you’re better off with a Busse.

 

[rodriguezryan14]

I just recently got confirmation about this the other day too. My purchase was like 7.8 percent chromium I believe!!

The composition of A8 mod was (is?) listed incorrectly on the AKS website. There has never been a 5% Cr A8 mod. If such a steel was tested it wouldn’t have worse toughness than A8 mod anyway.

 

[scdub]

Let's say that for toughness, S7 is a ten, and ZDP-189 is a three. What is INFI?

I’m partial to choppers in tough steels, and have had a good deal of wood chopping time with several knives in 5160, and one each in SR7 (S7), and INFI (the AD6 that you re-ground for me).

In my experience, at similar HRC, the INFI edge seems slightly less prone to edge deformation than either 5160 and S7 (but it’s difficult to assess - the INFI blade is thinner but also lighter/shorter than the knives I’m comparing it to).

The main claim to fame however I believe is lateral strength. I don’t have the post/article or whatever (someone might have it that can post a link), but many years ago Jerry apparently did a live demonstration where he bent one of his INFI knives to a certain degree and it returned to straight. In my recollection, he essentially challenged other companies to attempt the same feat, and unless I missed something nobody has yet taken him up on it.

Also there are those old Noss videos…

 

[hugofeynman]

I’m partial to choppers in tough steels, and have had a good deal of wood chopping time with several knives in 5160, and one each in SR7 (S7), and INFI (the AD6 that you re-ground for me).

In my experience, at similar HRC, the INFI edge seems slightly less prone to edge deformation than either 5160 and S7 (but it’s difficult to assess - the INFI blade is thinner but also lighter/shorter than the knives I’m comparing it to).

The main claim to fame however I believe is lateral strength. I don’t have the post/article or whatever (someone might have it that can post a link), but many years ago Jerry apparently did a live demonstration where he bent one of his INFI knives to a certain degree and it returned to straight. In my recollection, he essentially challenged other companies to attempt the same feat, and unless I missed something nobody has yet taken him up on it.

Also there are those old Noss videos…

The blade was a Battle Mistress and he bent it to 35 degrees. But today there’s other makers that can duplicate that. For instance, Carothers bent his light chopper to 90 degrees and it almost returned straight (as his k18 sword). There’s a toughness component in that test, no doubt, but it also as to do with the ratio between length and thickness. A tough steel, and the right knife dimensions. Larrin already explained that, I think, but I’m too lazy to search for it now.

 

[hugofeynman]

I’m partial to choppers in tough steels, and have had a good deal of wood chopping time with several knives in 5160, and one each in SR7 (S7), and INFI (the AD6 that you re-ground for me).

In my experience, at similar HRC, the INFI edge seems slightly less prone to edge deformation than either 5160 and S7 (but it’s difficult to assess - the INFI blade is thinner but also lighter/shorter than the knives I’m comparing it to).

The main claim to fame however I believe is lateral strength. I don’t have the post/article or whatever (someone might have it that can post a link), but many years ago Jerry apparently did a live demonstration where he bent one of his INFI knives to a certain degree and it returned to straight. In my recollection, he essentially challenged other companies to attempt the same feat, and unless I missed something nobody has yet taken him up on it.

Also there are those old Noss videos…

In old Noss videos, the less thick Busses didn’t scored so well. I think he gave the Basic 10 5,5 swords (the Battle Mistress received 7 swords (stars), the max he ever gave to a knife, the exact same score he gave to Keffeler monster in 3v). As a comparison, he gave 5 swords (stars) to Falkniven A1… Unfortunately, all this is long gone, but it lives in the mind of some “old timers” like me.

 

[ace]

The problem with all these tests and in general testing knives against each other in non scientific manner is that you are not just testing the steels against each other, so you can't really make conclusions about the steels. In all these tests geometry makes such a huge difference that as fun as these tests are to watch and do very little information about the steel performance can be determined. To illustrate this point here are a few examples. You can take a fillet knife made out of some steel used in knives and bend it to 35 degrees and it will come back to true, you can probably bend it to 90 degrees and it will come back to true as well. What does it say about the steel? it says that you haven't exceeded the yield stress of the steel, but that's about it. In another example cold chisels are used to cut metals and masonry without much deformation and there is nothing very special about the steel they are made out of, but the geometry of their edges allows them to do this. Unless the geometry is the same for 2 different pieces of steel, you can't make conclusions about steel attributes. Another problem with chopping test for example is that there is no consistency to them. When you chop dried logs with different knives the logs are not uniform, the strikes are not uniform, the force is not uniform all you can say is that one knife works better for you than the other, but not that one steel is better than the other unless everything else besides the steel is the same.

Badly done "real world" testing is how we get to myths that 1095 is a tough steel or that low alloy steels are always tougher than high alloy steels or many other misconceptions. All because of badly designed tests and the lack of understanding of what is being tested.

This in no way implies that you need to buy new knives or use different steels or that some steels are bad. If the knife works for you then it doesn't really matter what the steel is. It doesn't matter that 1095 is relatively brittle, as long as it is tough enough for the application that is all that matters. Conversely if the knife works for you that doesn't mean that the steel it is made out of is tough or anything else as compared to other knife steels. It just means that it is good enough for your use.

 

[David Mary]

Anecdotal observations are not worthless. And that’s what I asked for. Thank you to all who have provided your observations, I feel enlightened for it, which was my purpose in starting this thread.