Pics of edge damage from concrete & steel

[the possum]

I know I've spoken about this in the past, so I thought I'd share with ya'll, and see if this is what you'd expect from your own knives.

I was stalking a coon back by the Harvestore sheds, when my dad decided to fire up the 4-wheeler and come look for me. He scared the coon right toward me, but I didn't have time to get in perfect position. I ended up chasing the coon around the silo and cattle chute, through lots of tall weeds. I took a couple quick swings at him when he tried climbing up the cattle chute, and I hit the concrete pretty good. This swing was not reared back with full power, since I had to be quick, but it was still good enough to send sparks flying two feet. I missed as the coon jumped down, and he ran along on a big, rusty steel pipe that was laying there for some reason. Twice again I missed him as he ran through the weeds, and my blade clanged loudly on the steel pipe. I finally caught up with him near the cattle shed, and cut him down good & proper.

As I was chasing him, my dad was watching the whole time, and when he saw the sparks fly and heard the strike of steel on steel, he hollered to let the coon go. "Don't ruin your blade over that coon!" he yelled. The moment the action was over, he said, "Alright, lemme see what you did to your knife." I wiped off most of the blood in the grass, (that's blood still on the blade in these pictures) and examined the edge with our flashlights. This is what we saw.

Dad said he thought it would have been a lot worse. Though it will take some time to sharpen out, overall I'm pleased that at least I didn't lose big chunks out of the main grind, like probably would have happened with my old stainless knife.

I'm just wondering, for those of you who have done such testing, does the damage above seem like what you'd reasonably expect from this situation? Have you noticed less or more damage?

 

[Cutshaw]

Sweet Gentle Geezus, I can picture this...

I think I'm scarred. (No, not "scared", scarred.)

Wow...

 

[James Green Dragon]

...Dude, why is it that you were killing a racoon with a knife? That is truly fvcked up

 

[the possum]

Well thanks for the sentiments, guys. Best stay away from the Practical Tactical forum, where they discuss using knives on people.

As to why I'd use a knife, I've covered this in the past.
I was in an area where I couldn't use the pistol on my hip, because it was too unsafe. I was surrounded by expensive machinery I didn't want to destroy, and hard surfaces that could cause ricochets. I was also 10 feet away from a pen of a couple hundred cattle, and a shot could make them stampede. Besides, the knife is more effective within its range, anyhow. The coon had just been wreaking havoc in the feed room, and I didn't want that. They are nuisance varmints, which is why I try to get rid of 'em.

I am posting this here, because I've seen plenty of people moan and prattle about the uselessness of concrete chopping and other destructive tests. This information is indeed relevant to my particular situation. I gave the details (about using it on a coon) up front because I didn't want to deal with a dozen replies from people assuming I was doing a useless "test".

 

[Gossman Knives]

That situation is an unusal circumstance. Any sane person would not purposely do that with a knife. The damage you experienced doesn't surprise me. Knives are not designed to cut steel so this IMO is not a valid test. You're lucky that's all the damage it sustained. You've got yourself a fun job getting those dings out of the blade.
Scott

 

[knifetester]

What knife? Blade steel, hardness, profile?


[Note thread edited to delete a comment that was out of line, and out of character for me. I apologized to Possum later in the thread, and further cleared up matters in email. I suggest everyone check out his website before jumping to conclusions, like I did, about his raccon slaying.]

 

[Cougar Allen]

Some of you guys could have a look at Possum's website. He's not crazy or cruel; he's dealing with a pest problem more effectively than most farmers. (Most just curse and throw things at raccoons when they come nose-to-nose with one in a situation where they can't shoot them).

His knife didn't survive so well just by luck, either; choice of steel and heat treat has more than a little to do with it.

 

[Joe Talmadge]

Seemed to come out okay. I'm interested in what the knife is, and the blade steel. The damage looks exactly like what I saw when I accidently made some hard chops into some concrete with a 3V knife, though that knife had a scandanavian grind (not to worry, it was Cliff's knife ).

 

[kaosu04]

I agree with Cougar Allen. He was just protecting his property. Why let a little raccoon mess up the way your entire farm works? I'd kill it too.

 

[roughedges]

I agree with Cougar Allen. He was just protecting his property. Why let a little raccoon mess up the way your entire farm works? I'd kill it too.

yep. and I'm an animal lover too.


the knife looks like it survived the concrete and steel real well possum. like everyone else, what knife? what steel?

 

[Cliff Stamp]

Have you noticed less or more damage?

Both. Some stainless steel knives will fracture readily and under repeated impacts the damage can readily propogate into the primary grind. On a solid tool steel with a high toughness and ductility the edge will smear and dent. What concerns me with the edge pictures is that some of the damage is a little angular which generally points towards fracture, even if you remove the visible damage there can be cracks left.

Based on the pictures, the damage is constrained to a low penetration depth so I would consider a small secondary edge bevel significantly more obtuse than the primary edge grind, and about half the width of the existing damage. You could apply this after grinding most of the damage out, it would not only save grinding time, but act to reduce damage in the future, and as the bevel is still very narrow it will only slightly reduce cutting ability.

That situation is an unusal circumstance.

The end result, accidental high stress inclusions happen all the time working with large blades clearing brush as it is common to hit rocks and debris. This is why many of the older blades used for such purposes were left very soft so you could hamer out dents and resharpen the knife with little metal loss.

Knives are not designed to cut steel so this IMO is not a valid test.

It wasn't a test, it was normal use of that knife, and it was designed by the user to do that, and yes lots of steels used in knives were actually designed to be able to take large shocks and minimize the damage, and some knives are actually designed to cut metals as well, M2 and D2 are steels commonly used to cut other steels for example, as well as heavier impact steels in cold chisels and the like.

You're lucky that's all the damage it sustained.

No, the damage is minimal because of the properties of the steel and the heat treatment.

...cruelty towards animals ...

Many of the practices of farming can seem cruel to animals have you not been under the same constraints. Many of the people around here who raised sheep, chicken, and ducks for example did not look kindly towards cats and dogs on their land and would shoot them on sight. There are a few foxes around here which I look on with a neutral outlook, one of my neighbours who recently lost a breeding pair of ducks to one doesn't have the same viewpoint.

-Cliff

 

[Gossman Knives]

Ok Cliff let me rephase that, being that it was under normal use and was an unusual circumstance. Possom hitting the metal pipe was not intentional so the damage is understandable because you would not deliberatly chop on a metal pipe. The blade did fair well for what it went though. Yes I KNOW D2 and M2 are used in the tool and die industry to cut other metals but we're talking about a knife here not tooling on a machine. You are too much.
BTW, possom, have at those varmints. All they do is cause problems for farmers and carry disease.
Scott

 

[the possum]

Just out of curiosity, for those who asked about the steel type and such, does it matter? Not trying to be smart there, really. I'm just wondering if you're preparing a stock answer that it would have been better/worse if it was made from xxx steel, when I was really hoping to hear your experiences. But if you're just genuinely curious, the knife is a big Bowie (24"overall) I ground from 5160. I had Joe Walters heat treat it to form bainite @ ~56 or 57Rc, but unfortunately this piece of steel turned out to be rather inconsistent. I went into more details in this thread for those interested.

Any sane person would not purposely do that with a knife.

Never claimed to be sane, but this wasn't on purpose all the same.

Knives are not designed to cut steel so this IMO is not a valid test.

As Cliff mentioned, this was no "test". And as a matter of fact, I did design this knife with the knowledge that it would have to face steel and concrete. You may not recall it, but in this thread I asked for design input on a knife that could survive chopping steel.

You're lucky that's all the damage it sustained. You've got yourself a fun job getting those dings out of the blade.

Already done. Took 15 or 20 minutes with a very coarse alumina stone (by hand) including a few interruptions.

Edit- Scott, you must've been typing while I was writing this. No hard feelings, man.
Cougar, Joe, kaosu04, roughedges, and Cliff-
Thank you for the kind words of understanding.

Knifetester-
I agree cruelty to animals is a bad thing. That's why I'm using the most effective and quickest means at my disposal to dispatch them. Really, I have no idea where you're coming up with such accusations. Since you don't know me, that's about the nicest thing I can say at this point.
Don't take this personally, but I do get tired of trying to explain/defend myself to people who have no idea what they're talking about, though.

Good to hear from others that this is not unusual. I didn't believe it to be, but then there's several more shock resistant steels out there I've never used.

What concerns me with the edge pictures is that some of the damage is a little angular which generally points towards fracture, even if you remove the visible damage there can be cracks left.

Yeah, that bothers me, too. However, it didn't look like the edge chipped or broke away, exactly. The bottoms of those nicks were not freshly broken steel; they were smeared over. It's almost like tiny pieces chipped away, and then the remaining steel got mashed as it continued in the cut. By the way, this concrete is like 50 years old, made with coarse sand. That could help explain the ragged look.

Based on the pictures, the damage is constrained to a low penetration depth so I would consider a small secondary edge bevel significantly more obtuse than the primary edge grind, and about half the width of the existing damage. You could apply this after grinding most of the damage out, it would not only save grinding time, but act to reduce damage in the future, and as the bevel is still very narrow it will only slightly reduce cutting ability.

I appreciate you taking the time to offer constructive advice.
Right now I'm running a very coarse grit convex edge. It pretty much blends into the main grind, and gets to maybe around 30 degrees towards the edge, with an even steeper microbevel. In the past, I did some testing and decided I didn't want to make the edge any steeper/thicker, or I'd start compromising cutting ability more than I wanted. My goal is to cut well, and take some damage from hard substances, but confine that damage only to [the lower portion of] the edge bevel and not the primary grind. In all fairness though, it's been several years since I did those tests, so it wouldn't hurt to revisit the issue.

 

[martin j]

Amazing, when people damage a knife in testing it is not " real world," then if you damage it in real world situation it is " invalid testing" or "unusual circumstance." I don't think Cliff or Possum are the unreasonable ones here
The most surprising part of all this is imagining a possum chasing a raccoon. I didn't even know possums can carry knives. Much less own a farm.

 

[allenC]

I was LMAO picturing you chasing a coon with a knife!

Anyway, thanks for sharing the pictures.

Allen.

 

[knifetester]

Knifetester-
I agree cruelty to animals is a bad thing. That's why I'm using the most effective and quickest means at my disposal to dispatch them. Really, I have no idea where you're coming up with such accusations. Since you don't know me, that's about the nicest thing I can say at this point.
Don't take this personally, but I do get tired of trying to explain/defend myself to people who have no idea what they're talking about, though.
-

I apologize. I wrote in haste, rather than looking at the circumstances. I made assumptions that were in error and I was wrong. I am sorry.

As for the knife, it looks like it held up well considering the impacts it was subjected to. Also, it is a good looking blade, nice work.

Having stuck my foot in my rather large mouth, I will set the rest of this one out.

 

[Burchtree]

Good looking blade, it looks like it has held up well for the purpose you intended it for.

 

[the possum]

Knifetester, thank you for the chivalry. All is well between us. I welcome you to stick around if you have some knife related input.

Thanks, Burchtree.

Allen-
You'd laugh even harder if you'd seen my fat a$$ panting and gasping for breath afterward!

 

[Gossman Knives]

No big deal Possum, I guess I misunderstood the intent of your thread and didn't know the purpose behind your knife. Great looking knife, good choice of steel. Sounds like you're having a good time with it. Nice job getting the edge back.
Scott

 

[Cliff Stamp]

...I'm running a very coarse grit convex edge.

Does a higher polish lose cutting ability on the flesh? I would be concerned about stress lines from the scratches and maybe consider a fully polished edge and then a very slightly secondary coarse edge.

With the jagged nature, yeah, it is hard to judge from pictures, and when you get hard inclusions in a soft base you can get some focused damage that may be a bit difficult to judge.

My goal is to cut well, and take some damage from hard substances...

Yeah it always comes down to how much cutting ability do you want to trade for reducing damage.

..it was under normal use and was an unusual circumstance.

Not really, he has described doing it on a fairly regular basis in the past, breaking one knife because of it, and grinding a large amount of metal off another because of accumulation. As noted, lots of large brush blades are ground with this in mind, it isn't unusual for it to happen, it is an accepted fact of use and blades were designed with it in mind.

Possom hitting the metal pipe was not intentional so the damage is understandable because you would not deliberatly chop on a metal pipe.

Maybe you would not with one of your knives, but lots of people make knives which are designed to actually chop on hardened metals, tactical knives intended to be entry tools, or survival, crash/rescue knives.

Why is it "understandable" if it happens in real use, but not if you do it to simulate it. Would it not be better to understand what your tool could do before you are actually forced to depend on it.

Justin of Ranger knives did a lot of testing on his Entry Tool in Iraq which was completely artificial because it didn't actually need to be done from a survival/mission perspective, he was just hacking and prying on concrete, car wrecks and such to evaluate the scope of work and further the design.

Is this "unreasonable", or just acceptable because he is a maker, and a user don't have the same rights?

Beyond this, lots of large knives while not designed to actually be used to cut rocks and metals, are designed with such impacts in mind as accidental high stress impacts. So again why would it be unreasonable to actually see if the tool can handle it by just trying it out, instead of waiting for it to happen which could risk gross failure and leave the user without the necessary tool which he depended on.

-Cliff