mrstabby
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Post by mrstabby on Nov 8, 2023 21:05:23 GMT
I know, it's a multi-facetted question depending on steel and heat treatment, but I am asking more about specific insances.
I am aware of differentially hardened swords being more likely to get damaged by bad cuts or abuse, having seen a few videos about it, but what does it take specifically on either DH or monotempered blades?
Just having seen some brutal tortiure test on Windlass for example I wonder, when they survive being used to chop down a tree, if a bad edge alignment hit on a 2l bottle could bend one for example. I have seen blades come bent from the factory, have seen bent and broken tangs, but not yet (hopefully never) a bent blade from a bad hit. After having to straighten some machetes, I am just wondering what it takes to bend one, because they did not get the bend back when I hit tham hard against wood. And it looked like they bent as far as I had to in order to straighten them, but a static load is probably different to an impact. So, I am interested in your experiences.
EDIT: Also having been accused of bending a 5160 blade by a seller, I would be interested, what I would have had to do to bend one by 5°
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Post by larason2 on Nov 8, 2023 23:59:48 GMT
I've only ever done it on differentially hardened katana and tanto blades. I made some Japanese style blade straighteners out of Elm. I made my holes a bit bigger than the Japanese ones, so what I do is arrange them both on the same side with the part to be bent between the straighteners (they are about 90 degrees from each other). Then I brace one on the inside of my leg kneeling on the floor bent over, and bend the other one around using both my hands, one to bend and the other to support. It takes a fair amount of force, you won't accidently do it unless it takes a bad cut on something really hard. The idea is to bend the shinogi though, which is soft metal. Align it properly and the ha will follow. I'll try making the holes smaller on the other end some day so I can try out how to do it as the Japanese do. For now this works.
I'm not sure I would try it on a through hardened blade, since I feel you're much more likely to break something on a hardened edge if you try to straighten it.
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LeMal
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Post by LeMal on Nov 9, 2023 0:08:47 GMT
Too facile answer: It depends. (A lot.) :p
Not just on steel and heat treatment. On target. (And sometimes environment. And exact matchup with target and blade geometry. And strike angle. And... Well, you get the picture.)
But that's life. Why did pothole (A) snap my axle when "worse" pothole (B) it weathered just fine? Why will making seatbelt X "give" by a few mm too little still pulp your insides while a few mm more and it'll save your life?
Just as a concrete example, I've had the exact same sword on (notoriously finicky) 2L plastic bottles cut through effortlessly, bottle after bottle, because once the "skin" is sliced it's a done deal, then lose a *smidgen* of sharpness--and get bent. A couple of times even snap the tang of that very same sword.
Which, to be fair, is why I HATE 2Ls. Because a feces-ton of testing I've done over decades on various targets but especially comparing them to meat cuts? Not only is the latter FAR more forgiving--even with bone (and, though it might stifle the cut, even more forgiving with fabric armor!). Cuts/swords that "fail" with bottles and/or tatami often are just damn fine on actual flesh.
In fact, this is one mountains-out-of-molehills thing I clearly see over the years in sword-geeking; not only do we misinterpret abusing testing (though for the record I'm actually a fan of it--knowledge IS a good thing) we don't realize that a lot of our "regular" testing materials can, with small differences in circumstances, *become* abusive in a non-realistic way.
Seriously though, it sometimes doesn't take a lot to damage a blade, which we then erroneously might label a "bad" one. Nowadays, I pay attention with curiosity to people's reviews testing all the way up to abusive, and all encourage it to indulge that curiosity, but if it's something I bought as primarily a weapon? It'll only touch smaller plastic bottles, cuts of meat, fabric, and wood consistent with shields, occasionally mail or plate over small bottles or meat.
At least until I have reason to fear the Ents' attack. *rofl*
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mrstabby
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Post by mrstabby on Nov 9, 2023 9:25:41 GMT
Yeah, meat isn't difficult, and living bone isn't a real problem either. I feel any substitute target we regularly use needs more sharpness, skill or both to cut. The only thing that meat does that bottles etc. do not as much is grabbing onto the blade and sapping energy from the swing. There is much variation in the bottle thoughness. Bottles from carbonated drinks are much tougher. The hardest around where I am are CocaCola bottles, they are twice as hard to cut than similar sized other soft drinks. The easiest are the cheap water bottles from Hofer. We don't have the big milk jugs available, so no idea how hard these are, though I have heard they are easier than PET bottles.
To be honest, I am not really getting why wood, which makes the blade stop hard, would be less dangerous than bottles. Not criticising you LeMal, I just don't get the physics. I'd imagine a hard target to be more resistant, giving back more force on a bad cut than a relatively soft bottle.
larason2, I think it depends with the through hardened stuff, if it's relatively hard you are probably gonna break it, but on swords with a good temper, I don't think you'll break it before it bends. Honestly though, I am not sure if you could straighten out a 6mm thick spring tempered blade by yourself. The 3mm machete already took all I had, even had to stand on it to straighten the tip.
I am still hoping for more stories how stuff like this happens.
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LeMal
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Post by LeMal on Nov 9, 2023 10:54:51 GMT
Oh, I'm definitely not saying that wood in general is better than bottles! I'm only talking of the thickness used in shields, which is pretty thin, and I'll only strike it with/into the grain, again like the edge of a shield. :)
The other thing that makes those 2L carbonated soda bottles porentially nasty, especially cap-on, if the blade is not "sharp sharp" in a way that historical blades weren't always kept but meat doesn't require, is back to the simple physics. IF that plastic ISN'T immediately sliced, you've got not only an incompressible block of fluid, but one of well over 4 pounds. Against a blade whose mass is a LOT more extended around the impact point, and, since it's traditional "design" preferences speed over torque... is at a severe leverage disadvantage.
As the saying goes, "something's gotta give." And it has to be either the target (and you're right, softer plastics can make a huge difference too) or it's gotta be the blade. Which you might get away with, spring temper, softer tang, other reasons... but you might not.
The irony though, again, being most a "real" or "historical" target *would* give enough not to worry. That target might not be cut or sufficiently damaged, but still, give.
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Post by larason2 on Nov 9, 2023 13:39:31 GMT
You're probably right. The nakago on my through tempered dojo pro is bent, and I've been meaning to straighten it, but I don't want to break it! So I have to decide if I want to risk it or not. Even DH blades sometimes crack when you try to straighten them, so it's always a risk. Still, I'm less scared of breaking DH blades because I have more experience straightening them!
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Post by crazyjons on Nov 9, 2023 14:01:17 GMT
That is a super complicated question, when you look at the manufacturer specifications for steel if the yield strength is very close to the ultimate strength that means there's just a tiny window to bend it without snapping it. I believe that is mostly related to the tempering process where an already quenched Blade is heated to a much lower temperature for a specified time.
With just a quickest bit of Internet research it looks like 5160 has a yield strength of about 40,000 PSI and an ultimate strength of 105,000 PSI, so that is quite a big window where you should be able to bend this hypothetical sword and have it stay bent instead of breaking. With that example I have no idea how long or at what temperature they tempered it at. That may be a completely un hardened example.
I have flexed a dojo Pro 1060 through hardened blade maybe 25° and it returned to true.
Jon
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mrstabby
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Post by mrstabby on Nov 9, 2023 14:45:32 GMT
I know it is complex, that's why I am asking for specific instances when it happened to someone. The only instance so far of a botched cut resulting in damage that wasn't intentional I have seen is Skallagrim bending a LK Chen White Arc Jians tip. And seeing the slow motion it's not really surprising, the tip was rotated and bent at the same time. Though his version is the 1060-t10 laminated version not one of their spring steel offerings. It's lso a very, very fine blade. Look at around 5 minutes, damage shown at 5:50
EDIT: Not the only instance, have seen a few Katana failing to cut tatami, the ony through hardened example EDIT2: I have seen an example of a breakage on the Arms&Armour channel, where they did edge-on-edge parries and instead of grinding out the nick he used the sword with some 3mm nicks in the blade and it broke at one of them. But he had expected this and did it FOR SCIENCE! Another break was the CS sword video posted here, but I am not sure that that was anything but bad luck.
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