In swords of all kinds, such grooves change the way the weight of the sword is distributed without weakening the sword and in English, are referred to as a "fuller". There is even a forging tool called a "fullering" tool, although, in the case of the katana, such grooves are usually produced by grinding rather than during the forging process. The idea that air resistance is a significant factor in actually using such a sword in combat is just silly. It would be useful to understand when in history such grooves appeared on Japanese swords as it would answer a lot of questions.
Fullers can be either ground or pressed during, grinding being the more common method as it's simply easier to do and doesn't threaten the forged piece as much.
@@matthewjay660 You mean, you have no idea what these guys are talking about? In French, meaning that this technical explanation in regards to metallurgy make no sense of understanding? Just relax and read carefully and try to make out what you understand.
I love that I never know what I’m going to learn about when you upload. I’ve always been fascinated with Japanese culture and your videos have been a great resource while I learn the language 🙏🏽
The ancient Roman spatha long cavalry sword that evolved into the iconic Viking long sword had a wide and deep fuller in the middle of the blade to save weight. The thickness of the blade was increased close to the edge, outside of the wide fuller groove, and this gave the blade strength and rigidity, like a cross-section of a modern steel I-beam girder is light while still being strong and rigid.
@@ssgoko88 Yes, there's that, but thick blades are heavy and unwieldy. The Roman Gladius short sword with her thick flattened diamond cross-section typically weighs more than a late medieval long sword that can be two feet longer (tapering to a point with two deep fullers along the central ridge).
this also answers why cutting masters don't want a fuller; a heavier blade has more cutting authority, and if what you intend on using the sword for is training in flowing, continuous motions as well as cutting tests, a heavy sword is no big disadvantage compared to the advantages it brings. This opposes to sparring where you might want a lighter sword. I won't speak about combat situations because I obviously don't know anything about that
It's amazing how so many things about weapons and architecture we construe with all these theatrical or mythological properties are really just there for the most practical of reasons.
My understanding is that the hie[sic], what is nominally referred to as a fuller in western swords, was meant to lessen the weight of the blade. The katana, as I understood it, was already a heavy weapon, so a fuller would reduce weight throughout the blade. (The fuller in Western broadswords, longswords, et al., have the fuller milled between the two blade edges which the katana does not have.)
I agree; my sources include Scholagladiatoria Channel and Tod's Workshop Channel, and while these are both Western (and arguably Eurocentric) sources, I believe that the physics and material science remains consistent despite different sword designs and uses.
The ability to pull it out easier probably shouldn't have much to do with air but friction. By having a groove, less surface area remains in contact with the surface of the stabbed one, much similar how ice skates slide on the surface by minimizing the amount of surface area between the rail and the icy floor. Although, I think it could make sheathing/unsheathing slightly easier by providing a channel for air to flow in and out of the sheath
Not quite true. The fuller / hi does reduce friction but this can be achieved by leaving hammer indents in the blade. More importantly it breaks the vacuum caused when pulling the blade out of a deep wound, thereby reducing stiction… WRT ice blades, the blade edge is ground to a hollow to allow a layer of water to separate the blade from the ice while maintaining directional control…
@@551taylor For a low pressure zone to form, it needs the cavity to have the structural integrity to withstand the pressure differential; this does not happen when piercing flesh, all the pressure does is pull the tissues together. What creates great resistence pulling a sword is bone and armor, not flesh
Shogo, thank you so much for the time and energy you put into every video. I recognized many of these reasons for Hi from videos I've watched on Western swords and blacksmithing, but several were new to me. I always make sure to watch your videos when my mind is ready to receive learning, because I can't watch your videos without coming away with new knowledge. However, I must agree with user Steven Moncivais and perhaps others, that weight was probably more of factor than the suction of removing a sword after stabbing. Swords that did not specialize in stabbing often had fullers, or grooves (such as the European Migration Era sword, or Viking sword), and longswords from later in European history that were very clearly intended for stabbing did not. I believe that these grooves are intended to both reduce weight and increase the rigidity of a bade. I have heard that the steel used to make the sharp edge of a katana blade was much harder, but more brittle, but the steel used for the core of the blade and its blunt edge were made of softer, more flexible steel. To my mind, a Hi groove would increase the rigidity of the softer steel without adding more material or compromising flex. Thank you for reading this. I have the utmost respect for what you're doing as an expert culture-bearer, and I'm so glad that I found your channel. Sincerely, An insufferable sword otaku
From a smithing perspective, adding a fuller in the traditional European way makes the blade wider in a safer way, adds a lot of structural integrity, and doesnt actually remove any material. You smith the fuller, not carve it. I dont know about katana, but this is at least what's done for European swords.
It's not because you smith it rather than carve it that it is not for weight reduction. You just start with less material to begin with AND smith the fuller to maintain structural integrity.
As a chef I can attest to the effect of having a groove or bumps on a blade in relation to making them less "sticky". And you don't have to be a chef to know just how much a potato can stick to a knife if it has a completely smooth surface xD
I am not sure what they are doing in Japanese kitchens these days but it is my understanding that katana were not traditionally used to prepare veggies.
As someone who has had the displeasure of being in a knife fight and actually stabbed live human flesh, I really have to question this. One thing that stuck with me is how unbelievably little resistance the human body poses to a pokey thing. Once the skin is punctured, it requires minimal force. In fact I actually thought I missed my thrust because there was so little resistance. I can't possibly imagine a blade getting stuck in soft tissue. Unless you get it stuck in bone, it's just gonna go straight in and out of a human body. And I don't think the groove will help with getting stuck in bone.
@@mrkiky thats because ya used a knife mate. A knife is relatively short and a much different blade than a katana. As he said in the vid it's hard to remove a katana that's been thrust deeply into a person. So your current for knives but not katana bloke
The actual weight of a weapon is a very important consideration for militaries. A soldier has to carry a weapon for days, weeks, or months for every hour actually spent attacking with it. A bit of wind resistance seems a fair trade to lighten a weapon by 10%
Honestly, 10 % would be like 150g, thats about the weight of an empty G3 aluminium magazine or 1.5 bars of chocolate. Not really that noticeable. There would be much more weight to be saved on other equipment.
@@wernerviehhauser94 swords generally are held away from the body tho. 150g are enough to make a big difference in a combat stance and i dont think that there is no difference while having it on the hip aswell
@@MovieFactory take the time to take a look at how large the mass differences between swords actually are, and you'll notice your argument has no basis.
@@wernerviehhauser94 i do think i have a basis. nobody is carrying around a zweihänder all the time, but bastardswords? sure. they are usually 1.5kg and are pretty heavy, i know that because i train with one, a fu,00ller is a really big help to distribute weight and make it feel lighter in actual usage. same with even smaller blades ala estoc. removing just a few gramm has a noticable difference in usage. no matter if its 1.5kg or just 1kgsomething over 2.5kg usually wouldnt have been carried around (atleast in europe)
The main reason for a Hi, or what we call a fuller, on a Western sword, is to reduce weight. There are three reasons why this matters. 1. For 90% of a sword’s life it is not a weapon, but just mere luggage! Lighter is better. 2. If 90% of the time it’s luggage, 9% it’s parade jewellery. Ever tried carrying a sword on parade? You’d give anything for a lighter sword, literally anything! 3. If it’s ever actually used as a weapon, you need all your strength to stay a alive. A light, lovely weapon is your friend! A heavy estoc would tire you too quickly!
Lighter weight means less tiring and better control. A heavier sword rarely creates a benefit to the user regardless of its type. It's interesting that you mention it as jewelry because I can absolutely see your point I've just never considered it having only used one for sparring. I can see how you'd be tired before starting if you had to lug it around all day before even thinking about a fight.
I personally think that they are to reduce weight while retaining as much strength as possible. If we look at other weapons like the tanto or as mentioned the yari, they have grooves as well. These weapons are mainly used for stabbing rather than cutting so air resistance while swinging it wouldn’t be an issue. For swords in other parts of the world, some of them have their grooves hammered out instead of ground like the Japanese did. This increases the width of the blade while keeping its thickness(except for the groove part). A thicker and wider blade would be stronger but heavier, the addition of a groove achieves the 2 benefits without the weight. Its “I-beam” shape also helps it remain strong even with a thinned portion.
Hi Shogo , I remember something about an emperor getting sick of body parts being left rotting on the streets so he made a law that swords could not be as heavy anymore and must stay below a certain weight in hopes less limbs would be completely severed. Apparently there were people who’s job it was to drag bodies off the street but they wouldn’t come back for the limbs ( dogs usually got them) In order to lighten the swords without making them shorter or thinner they used the groove. I think it’s always there for different reasons for example, if you forge in the groove you are making the most out of your precious material, and they did that. If you grind or scrape the groove in then it wastes material, and they did that in later times when material was more available. But I think it was originally done to lighten the blade to make it less powerful and legal, then later the reason was lost to the people. It was just to meet legal requirements during that emperors reign in Japan but sword makers kept doing it after because that’s how they were taught to do it. Is this true ? Do you know who that emperor was ? Maybe you can research for the details. It’s not in sword manuals or anything it’s just a bit of history that gives a clue leading you to the answer. It’s something that is only realized when the scholars swordsmiths and swordsmen get together and put their pieces together revealing a large chunk of the puzzle 🧩
I understand the weight and structural arguments have the most merit. The suction argument might too (not as familiar with that one). But the decorative aspect shouldn't be fully discounted. Something can exist for practical reasons; that doesn't mean some people, especially those with means, don't desire them to be attractive as well. An extreme example are some cinquedea daggers from Renaissance (early modern) Italy, some of which feature multiple fullers in elaborate patterns. But there are examples of other swords, knives, and daggers with multiple fullers in a pleasing pattern, or fullers decorated with paint, gilding, or etching.
- For mat-cutting the grooves might catch the fibres and throw the cut off, unless your alignment is absolutely perfect. That's probably why it's less ideal, but that won't apply to combat in the same way. - When it comes to thrusting I don't think the grooves make that much of a difference. Your main target would be the torso, which is not a solid block of meat, but mostly hollow, with air-filled lungs and organs that can be moved. More likely, the blade might get stuck between the ribs/bones or the blade might bend when a body slumps over. Grooves won't change that. - weight reduction/distribution seems the most likely reason (at least it is for western "fullers"), although I'm willing to concede, that the exact form and nature of the groove in question will dictate the purpose.
I always assumed the _hi_ (or similar pieces) was almost purely decorative. I would buy the weight argument, though. As another martial artist pointed out, “you were wearing or carrying your weapon far more often than actually using it”.
Hi Shogo! I've been a fan watching your videos for just over a year now, and I just wanted to say that of all the awesome TH-camrs I watch, whether the topic is historical, cultural, music related or healthcare (my field of work), you have the absolute best introduction of them all, with your greeting and bow! And I love all your videos, the way you typically structure them is so great. And they're very informative - hopefully I will find them especially useful when I can finally visit Japan, such as etiquette and all the cool places that a visitor should not miss out on. Doumo arigatou!
The groove is for a vacuum break not only to remove from saya or scabbard and also when cutting through flesh. Some of my kitchen knives have grooves that help when cutting. Just yesterday I was cutting a watermelon with a chef's knife without grooves and the blade got stuck in the flesh of the watermelon.
I also questioned about the real purpose of the groove on the katana. I found the main purpose of the groove is for quick drawing after a stab in a bloody battle. Like other weapons with a groove, the air coming through the groove help users to draw the sword out of the wound easier. In addition, the sword would absorb a strong impact if it hit a hard object/ another sword. The groove with a week thin layer of metal could absorb the impact from the hard front blade to the soft metal on the groove. It would keep the blade not broken. For all of those reasons, why the groove would go all the way along the blade is another question that I am looking for an answer.
On some knives, the grooves are only for optical purposes. There is also the aspect of moving mass from the center line outwards, allowing for a thicker or wider blade, increasing the torsion resistance while keeping the mass of the weapon the same. The point of making it easier to pull the blade out after stabbing seems legit - you could try that on a nice pork side and turn it into teppan yaki afterwards :-) And then there is the fact that humans are creatures of habit, maybe the grooves had a reason to be there on older blades, and they have just been copied without a real reason but because bladesmith - now and then - believed to know things that were effectively not true but nobody noticed.
All due respect, Shogo, everything I've found points to the simple answer of reducing weight while maintaining most of the structural integrity/rigidity. Nothing to do with stabbing as the earliest blades with grooves tended to be wide bladed cutting swords very often with rounded tips.
I think people choose or avoid it for any of the said reasons. All the time I always thought to myself: "What if once someone just created a Hi as a decorative element of his blade, because he wanted a simple, but nice looking decoration, and others liked it and wanted one too? Maybe the question for the use of it came much later?" I know that historical weapons are often simple and their Parts for a reason, but such a grove is in my eyes, the simplest way to decorate a weapon without puting it off balance like a decorative pommel, uneaven Guards or complex engravings cold do.
You are correct 100 %. The grooves are made by using a "pinching" tool while the metal is hot. This isn't a matter of removing steel. Therefore, it removes NO weight at all. The shape does (as you mentioned) create a stronger structure at the spine of the blade. It was the practice to cover the spine with clay before quenching. This hardened the cutting edge while giving the spine a softer temper. This allowed the blade to bend rater than break when striking a surface with force. So no, the pinching process removed NO weight from the blade.
I think if we are talking about an actual sword used to kill in combat, the benefit of the Hi would be what Shogo said, it creates less friction, this also applies to Batoujutsu (sp?) , where you attack by pulling your sword from the sheath quickly as part of the swing. I guess the other commenters are only thinking in terms of Western weapons, or they are thinking more along the lines of a decorative sword that's mainly used for practice and ceremony, where the weight would be of a higher importance. I think the bigger improvement comes with the lack of friction. However, like Shogo also said, it probably depends on what you want to use your sword for as to whether or not you want one with a Hi or not.
You keep asking me to play at 1.25 or 1.5 speed but the way you speak actually helps me pay attention and the more time I spend on your video the more money you get
I believe this is the correct answer. I have done some bladesmithing in the past and adding a fuller is designed to reduce the overall weight of the blade.
It is likely but lets not jump to conclusions First of all this is a katana not a longsword, it might be different, i dont think any of us here know And in longswords the fuller is also added to be able to make the two edges more acute, not only for weight reduction. On a katana there is only one edge, idk how this makes the "fuller"'s purpose different Again yall might be right that its to reduce weight but i think we need to do more research
@@idkwhatthisisforplzhelp3678 Fullers are commonly added to many styles of knives, daggers and short swords which negates your point about the longswords. The above examples also may have 1 edge like bowies and bayonets blades.
The muscles will spasm around the blade making it difficult to withdraw. Twisting the blade allows the Hi to break the suction and get your sword back for the next ninja.
It’s purpose may also be to make it easier to sheathe the sword without looking, because you feel with your finger when the Hi ends, so you can look around if you missed some enemies or other threats
I used to see katanas like a cool iron stick-sword. But after watching these you can see that how much people thought on a sword just to make it more usefull
I thought the groove on the katana was to guide the fingers and the blade when sheathing, so we can sheath the katana without even looking at the blade and the sheathe
I like the idea, but I've used swords with and without - there's no real difference in feel while swinging. The curve shape and length, blade shape, and handle + tsuba do have a great effect on that feeling.
@@derikduley7806 The weight of a blade is just as much a contributing factor when it comes to balance and weight distribution. It does make a difference even though it's not the only factor.
Shogo thank for your videos, I agree with you, when a sword or long blade is stabbed it is difficult to put out, so the Hi, help remove the blade. Thanks again, Sayonara!
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The groove in a sword seems to have two main purposes: to reduce the weight and to increase the strength. A large groove can reduce the weight by 30%. But it also has the function of stiffening the blade (especially when used with proper heat treatments). A blade with a groove will not bend laterally so easily (since it becomes like an "I-beam"), so it becomes much stiffer and therefore more deadly (when used by an expert). A grooved blade is a much more deadly weapon than one without a groove, because it can respond much faster to any input and it maintains its own integrity much better (being a much stiffer blade).
Stiffness is not increased, it's merely retained. After all, material has been removed so it can't become stronger. You'd have to change the overall geometry to achieve that. For example by creating a T-shape to increase lateral strength. That has its own downsides though.
@@youtubevoice1050 It does become stronger and stiffer because it becomes like an i-beam. The H-beam and i-beam are common engineering standards in construction because they are stronger and stiffer. That is just applied science.
@@nicholasbishop5892 It does not "become stiffer", because you're not adding a lateral reinforcement, you're merely removing material in a way that does not compromise structural integrity. That is a common misconception. An H-beam isn't stronger than a full beam. You can obviously forge the blade in a way to be stiffer BY including a fuller and leaving MORE material at either side of it, but you cannot reinforce an existing structure by removing material. In katanas I don't see the geometry being changed. If the spine of the blade was turned into a T-shape (called pipe-back in the west), then yes, it would be stiffer than a regular katana. But that is not the case here.
@@youtubevoice1050 There is a "relative" increase in stiffness, because we remove 20% of material but maintain the original stiffness (the same as it was before), if the fuller groove is properly made. That gives the lighter blade a much more effective response and action. That weapon is much more deadly than without a fuller groove.
What you said about the likelihood of remaining calm enough to hold your sword parallel or downward got me wondering if maybe those stances where originally developed for the tachi or even odaichi, in historical European martial arts the only time I've seen swords held that way is with long swords and bigger, which tachi where right around the same length as European longswords.
I don't think staying calm during a real fight was an issue. Most of the people using them surely were used to fighting and death. And yes, I also thought about those stances where you would have a sward in a "downward" position. As for stabbing, I remember some bits from European history that made an argument that the reason why the Roman empire was more successful on the battlefield than other nations at that time, was because the Romans preferred to make stabbing moves over slashing moves, and the mortality rates were higher with stabbing wounds over the slashing ones. So 'hi' being used to make it easier to pull the sword out, seems very natural to me.
Saw this elsewhere in the comments but I have to say it again. The groove is for structural integrity. It redirects force along the length of the blade rather than perpendicular which could cause it to bend or break. This is an engineering basic to redirect force in a direction that the structure can handle. Any other reason simply does not have enough of an effect to warrant the design being so widespread.
Have to mention a basic experiment to test. Grab a normal piece of paper by the bottom edges and stand it up. It will most likely bend in the center and slump over. Now fold a groove in it. The paper will stand up straight without issue. The force is redirected in a straight path from the top to the bottom rather than wherever force is applied.
The perpose is to reduce weight. It's the same among all swords from any region that possess a fuller or groove. The releasing the vacuum thing is a myth and the increased air resistance is negligible compared to the difference in weight. Humans are squishy and wet on the inside. So the only thing that would make it difficult to pull out is if it's stuck in bone or cartilage and a groove won't help with that.
I never thought that my undying live for a video game, Ghost of Tsushima, would lead me to learning about Japanese culture and owning a newfound respect for the Samurai.
I am agree with the hi groove is for make easier when they pull the sword from the enemy body, but i rarely see a jutsu or kata their main attack only thurst the most i see a weapon with it in spear.
From my understanding the hi sometimes is made to correct the smithing of a blade. When a blade is heat treated sometimes the steel cracks and weakens the blade. So the bladesmith can remove and correct a crack by grinding it away. I'm not sure if, when corrected, it is done on both the omote and ura side of the blade, or just one side.
there is so much people in the comments talking about weight, but the inportant thing is the point of balance. A rapier is heavier than an arming sword but much more nimble because the point of balance is closer to the hilt. And of course the fuller if it's grinded is to reduce the weight and if it's forged to wider the blade or aesthetic.
I've always believed that grooves are to break the natural suction created between sword and wound. trying to remove a sword after stabbing is very difficult if the seal is perfect (ie no groove)
The body, especially the torso, is not a homogeneous block of meat though. So the resistance is smaller than you think. The blade might rather get jammed between bones, in which case the grooves won't help.
I disagree. I think it has more to do with integrity. Most blacksmiths I've heard ever mentioning fuller say they increase the durability and integrity of the blade. A fuller will generally make the blade stronger and stiffer. There is foreign weapons with fuller that do not have tips for stabbing or thrusting. While it is possible that weapons and cultures could have fuller for different intentions I would think that the fuller is most likely not only passed down technology but also convergent evolved technology. Cultures around the world most likely noticed these properties so generally the reasoning should be similar in most cases.
Thank you for someone who realizes that a groove improves structural stability. Try and stand a piece of paper up on its side it bends in half. Now fold a groove in it and do the same. The groove redirects force along the length of the blade rather than perpendicular to it. Engineering Fact.
I always thought it made it easier to cut with since it'll have less friction, like with European swords having multiple fuller lines it makes it's dimond shape flatter and have less resistance when passing through something
Hi (樋)is not Grooves (溝)but gutter (樋)in Japanese. Hi is the Japanese word for liquid drainage equipment. You can find the explanation by searching the words katana(刀) and hi (樋)in Japanese. "The muscles that receive a strong impact contract. The contracted muscles stick to the blade like a sucker. By letting air out of the Hi , you can pull out the blade from the muscles that stick like a sucker. " In the story of a samurai, an immature samurai stabs katana deep into the enemy's body,However, since it is difficult to pull out katana from the body, there is a scene where the samurai is in a hurry when he sees the next enemy.
Fullers on western double edged blades can reduce the weight of the sword by up to 35%, and since it creates a near i-beam like cross section does so with extremely minimal compromises to integrity.
In regards to the durability, I think that depends on how the grove is made. If it is made by removing metal from the blade, I can see how durability would be a concern. But if it's made during the forging process by putting a metal rod over the heated metal and hammering in the grove, then the metal would be compressed and should actually be stronger in the grove. But I'm not a bladesmith and just offering a thought. I have seen a program on the History channel called Forged in Fire where they actually create blades and even try to recreate blades from history.
Well, grooves ARE made to reduce the weight, this is well-known fact Strongly curved sabers, for example, can't have grooves for easier pull after stab, because you can't stab with such curved blade
European sabers can be used for stabbing as well as cutting. The long, heavily curved sabers popular with ancient middle-eastern cultures, however, could not. Those particular swords had long, delicate bodies and angled handles that made it extremely difficult to thrust, nevermind the issue of structural integrity.
I always understood the channel in a blade was to break the surface tension in the meat. Making it easier to remove the blade. But if you just hang your blades on a wall and not use them I can see the mystery
To keep oil in when fighting mons- Wait. No. Forget it. I'm not Geralt of Rivia. I always wondered why swords in general had groves, and tbh I always assumed they were just cosmetic. The true function was... A lot more grim than expected...
Shogo, I have followed you for a while now. You have inspired the creation of my own channel devoted to Iaido and my perspectives on the art. I have not added any content yet because of some health challenges, but that will be coming. I also listen to your podcasts, the latest of which has the comments turned off. I am an academic with a Doctorate of Business Administration. I specialize in technology and innovation management. As part of my research, I study leadership and leadership theory. Acknowledging the strong potential for culturally-based intervening variables, I have some thoughts about leadership you might find useful I could share with you privately if you would like.
The Hi groove has exactly the same use as the groove of european longswords (eu sword in general) : unstabbing. To reduce the weight, there were other techniques used during swordsmithing like drilling a tunnel inside the blade at each side of the tang making it lighter and harder to break
It’s a weight reduction method I and those are very difficult to get correct when forging the blade so many have gone home on forged in fire cause they didn’t get those right or they got too deep with them and compromised the integrity of the blade
Did he mention reducing the overall weight? Consider the groove as Roman engineering of an arched tunnel. Why is an arch 'strong'. The blade has the strength of a much heavier blade with a thicker spine, while lighter because an 'arch' supplies the lateral strength which is the vulnerable direction for bending and snapping.
It actually widely agreed in european swordsmanship that weight reduction and mass redistribution is the reason you put fullers in blades. This is very well known in a lot of european blades, especially apparant in those of the military era.
🤔 About the hi making it easier to pull out the sword after stabbing. The problem i have with this theory is that rapiers for example were thrust centric swords and they had no fullers. Can anyone with more expertise than me explain that?
The fuller is all about weight. There is no way that the speed advantage of a 10% lighter blade could possibly be countered by "air resistance." Some blades would be unusable w/o their fuller design, not to mention that using less steel is economical (especially in historical periods). I don't know any katana smiths, but smithing is smithing and metal is metal.
Shogo, when and whom started putting the Hi on the sword? I have always thought it was to allow air to flow and allow you to pull the sword out of a stab wound.
The reason a skilled swordsman would eschew a Hi is that the Hi makes it easy for a sword to ‘swoosh’ where as a skilled swordsman can move his sword swiftly enough to ‘swoosh’ without a beginner’s aid.
Can we compare the concept of the need for the hi in a blade, to having two strings on a shamisen instead of three? As in, the shamisen can do its job with two strings, but it can't have the same function as one with three strings. And a sword doesn't have the same air resistance without a hi, but a sword doesn't at all need a hi. Thanks Shogo.
I think only one of the above. To lighten the blades and balance the blade. Noise is a modern construct. I doubt a samurai wanted their enemy to hear it coming.
I think the last thing on my mind is that my sword is going to rust, I'm too busy trying to stay alive just to survive the fight. Steel don't rust quickly, death is certain.
In swords of all kinds, such grooves change the way the weight of the sword is distributed without weakening the sword and in English, are referred to as a "fuller". There is even a forging tool called a "fullering" tool, although, in the case of the katana, such grooves are usually produced by grinding rather than during the forging process. The idea that air resistance is a significant factor in actually using such a sword in combat is just silly. It would be useful to understand when in history such grooves appeared on Japanese swords as it would answer a lot of questions.
Fullers can be either ground or pressed during, grinding being the more common method as it's simply easier to do and doesn't threaten the forged piece as much.
The Count of Monte Cristo, brother I hope you get your revenge. I used to teach this movie in French class.
Just wanted to thank you for taking the time to leave this comment which is a close enough approximation to the comment I was going to leave.
@@matthewjay660 You mean, you have no idea what these guys are talking about? In French, meaning that this technical explanation in regards to metallurgy make no sense of understanding? Just relax and read carefully and try to make out what you understand.
I would also really like to know when they appeared in Japan.
I love that I never know what I’m going to learn about when you upload. I’ve always been fascinated with Japanese culture and your videos have been a great resource while I learn the language 🙏🏽
The ancient Roman spatha long cavalry sword that evolved into the iconic Viking long sword had a wide and deep fuller in the middle of the blade to save weight. The thickness of the blade was increased close to the edge, outside of the wide fuller groove, and this gave the blade strength and rigidity, like a cross-section of a modern steel I-beam girder is light while still being strong and rigid.
I think it is important to remember that lower weight=fewer materials. For the Romans that meant a lot given the armies of 10000 soldiers or more.
@@ssgoko88 Yes, there's that, but thick blades are heavy and unwieldy. The Roman Gladius short sword with her thick flattened diamond cross-section typically weighs more than a late medieval long sword that can be two feet longer (tapering to a point with two deep fullers along the central ridge).
@@ssgoko88 that's exactly what comes to mind. Lessen the mass.
this also answers why cutting masters don't want a fuller; a heavier blade has more cutting authority, and if what you intend on using the sword for is training in flowing, continuous motions as well as cutting tests, a heavy sword is no big disadvantage compared to the advantages it brings. This opposes to sparring where you might want a lighter sword. I won't speak about combat situations because I obviously don't know anything about that
It's amazing how so many things about weapons and architecture we construe with all these theatrical or mythological properties are really just there for the most practical of reasons.
Couldn’t agree more. Super interesting
My understanding is that the hie[sic], what is nominally referred to as a fuller in western swords, was meant to lessen the weight of the blade. The katana, as I understood it, was already a heavy weapon, so a fuller would reduce weight throughout the blade. (The fuller in Western broadswords, longswords, et al., have the fuller milled between the two blade edges which the katana does not have.)
That's my understanding.
I agree; my sources include Scholagladiatoria Channel and Tod's Workshop Channel, and while these are both Western (and arguably Eurocentric) sources, I believe that the physics and material science remains consistent despite different sword designs and uses.
Except in the west, fullers were seldom milled. They were produced during forging. There's even a forging tool called a "fuller" or "fullering" tool.
@@MrMZaccone I learned something new today! HUZZAH!
I honestly didn’t know this. Thanks for sharing!
The ability to pull it out easier probably shouldn't have much to do with air but friction. By having a groove, less surface area remains in contact with the surface of the stabbed one, much similar how ice skates slide on the surface by minimizing the amount of surface area between the rail and the icy floor. Although, I think it could make sheathing/unsheathing slightly easier by providing a channel for air to flow in and out of the sheath
Not quite true. The fuller / hi does reduce friction but this can be achieved by leaving hammer indents in the blade. More importantly it breaks the vacuum caused when pulling the blade out of a deep wound, thereby reducing stiction… WRT ice blades, the blade edge is ground to a hollow to allow a layer of water to separate the blade from the ice while maintaining directional control…
@@551taylor For a low pressure zone to form, it needs the cavity to have the structural integrity to withstand the pressure differential; this does not happen when piercing flesh, all the pressure does is pull the tissues together.
What creates great resistence pulling a sword is bone and armor, not flesh
Shogo, thank you so much for the time and energy you put into every video. I recognized many of these reasons for Hi from videos I've watched on Western swords and blacksmithing, but several were new to me. I always make sure to watch your videos when my mind is ready to receive learning, because I can't watch your videos without coming away with new knowledge.
However, I must agree with user Steven Moncivais and perhaps others, that weight was probably more of factor than the suction of removing a sword after stabbing. Swords that did not specialize in stabbing often had fullers, or grooves (such as the European Migration Era sword, or Viking sword), and longswords from later in European history that were very clearly intended for stabbing did not.
I believe that these grooves are intended to both reduce weight and increase the rigidity of a bade. I have heard that the steel used to make the sharp edge of a katana blade was much harder, but more brittle, but the steel used for the core of the blade and its blunt edge were made of softer, more flexible steel. To my mind, a Hi groove would increase the rigidity of the softer steel without adding more material or compromising flex.
Thank you for reading this. I have the utmost respect for what you're doing as an expert culture-bearer, and I'm so glad that I found your channel.
Sincerely,
An insufferable sword otaku
From a smithing perspective, adding a fuller in the traditional European way makes the blade wider in a safer way, adds a lot of structural integrity, and doesnt actually remove any material. You smith the fuller, not carve it. I dont know about katana, but this is at least what's done for European swords.
That's a really neat thing I wasn't aware of! They are carved for katana, though.
It's not because you smith it rather than carve it that it is not for weight reduction. You just start with less material to begin with AND smith the fuller to maintain structural integrity.
In europe we used grinding and smithing for the fuller
As a chef I can attest to the effect of having a groove or bumps on a blade in relation to making them less "sticky". And you don't have to be a chef to know just how much a potato can stick to a knife if it has a completely smooth surface xD
I am not sure what they are doing in Japanese kitchens these days but it is my understanding that katana were not traditionally used to prepare veggies.
@@robertmickelberg3720 he means its helps prevent the sword getting stuck in the enemy.
As someone who has had the displeasure of being in a knife fight and actually stabbed live human flesh, I really have to question this. One thing that stuck with me is how unbelievably little resistance the human body poses to a pokey thing. Once the skin is punctured, it requires minimal force. In fact I actually thought I missed my thrust because there was so little resistance. I can't possibly imagine a blade getting stuck in soft tissue. Unless you get it stuck in bone, it's just gonna go straight in and out of a human body. And I don't think the groove will help with getting stuck in bone.
Chef's knifes have a different geometry though and are broader, too. Not quite the same.
@@mrkiky thats because ya used a knife mate. A knife is relatively short and a much different blade than a katana. As he said in the vid it's hard to remove a katana that's been thrust deeply into a person. So your current for knives but not katana bloke
The actual weight of a weapon is a very important consideration for militaries. A soldier has to carry a weapon for days, weeks, or months for every hour actually spent attacking with it. A bit of wind resistance seems a fair trade to lighten a weapon by 10%
Yeah I agree. It’s more practical
Honestly, 10 % would be like 150g, thats about the weight of an empty G3 aluminium magazine or 1.5 bars of chocolate. Not really that noticeable. There would be much more weight to be saved on other equipment.
@@wernerviehhauser94 swords generally are held away from the body tho. 150g are enough to make a big difference in a combat stance and i dont think that there is no difference while having it on the hip aswell
@@MovieFactory take the time to take a look at how large the mass differences between swords actually are, and you'll notice your argument has no basis.
@@wernerviehhauser94 i do think i have a basis. nobody is carrying around a zweihänder all the time, but bastardswords? sure. they are usually 1.5kg and are pretty heavy, i know that because i train with one, a fu,00ller is a really big help to distribute weight and make it feel lighter in actual usage. same with even smaller blades ala estoc. removing just a few gramm has a noticable difference in usage. no matter if its 1.5kg or just 1kgsomething over 2.5kg usually wouldnt have been carried around (atleast in europe)
The main reason for a Hi, or what we call a fuller, on a Western sword, is to reduce weight. There are three reasons why this matters.
1. For 90% of a sword’s life it is not a weapon, but just mere luggage! Lighter is better.
2. If 90% of the time it’s luggage, 9% it’s parade jewellery. Ever tried carrying a sword on parade? You’d give anything for a lighter sword, literally anything!
3. If it’s ever actually used as a weapon, you need all your strength to stay a alive. A light, lovely weapon is your friend! A heavy estoc would tire you too quickly!
This is the best explanation I've ever seen
Lighter weight means less tiring and better control. A heavier sword rarely creates a benefit to the user regardless of its type. It's interesting that you mention it as jewelry because I can absolutely see your point I've just never considered it having only used one for sparring. I can see how you'd be tired before starting if you had to lug it around all day before even thinking about a fight.
its not 90% of the time its 99% of the time. 😂
VERY WELL THOUGHT. YOUR CHANNEL IS REALLY INTERESTING ON THE TOPIC.
I love your channel so much shogo! I hope you are doing well and I hope the family is as well. Keep the content coming!
I personally think that they are to reduce weight while retaining as much strength as possible. If we look at other weapons like the tanto or as mentioned the yari, they have grooves as well. These weapons are mainly used for stabbing rather than cutting so air resistance while swinging it wouldn’t be an issue. For swords in other parts of the world, some of them have their grooves hammered out instead of ground like the Japanese did. This increases the width of the blade while keeping its thickness(except for the groove part). A thicker and wider blade would be stronger but heavier, the addition of a groove achieves the 2 benefits without the weight. Its “I-beam” shape also helps it remain strong even with a thinned portion.
Excellent analysis! Thank you Shogo!
Hi Shogo , I remember something about an emperor getting sick of body parts being left rotting on the streets so he made a law that swords could not be as heavy anymore and must stay below a certain weight in hopes less limbs would be completely severed. Apparently there were people who’s job it was to drag bodies off the street but they wouldn’t come back for the limbs ( dogs usually got them) In order to lighten the swords without making them shorter or thinner they used the groove.
I think it’s always there for different reasons for example, if you forge in the groove you are making the most out of your precious material, and they did that. If you grind or scrape the groove in then it wastes material, and they did that in later times when material was more available.
But I think it was originally done to lighten the blade to make it less powerful and legal, then later the reason was lost to the people. It was just to meet legal requirements during that emperors reign in Japan but sword makers kept doing it after because that’s how they were taught to do it.
Is this true ? Do you know who that emperor was ?
Maybe you can research for the details.
It’s not in sword manuals or anything it’s just a bit of history that gives a clue leading you to the answer. It’s something that is only realized when the scholars swordsmiths and swordsmen get together and put their pieces together revealing a large chunk of the puzzle 🧩
I understand the weight and structural arguments have the most merit. The suction argument might too (not as familiar with that one). But the decorative aspect shouldn't be fully discounted. Something can exist for practical reasons; that doesn't mean some people, especially those with means, don't desire them to be attractive as well. An extreme example are some cinquedea daggers from Renaissance (early modern) Italy, some of which feature multiple fullers in elaborate patterns. But there are examples of other swords, knives, and daggers with multiple fullers in a pleasing pattern, or fullers decorated with paint, gilding, or etching.
That's something that I understood by myself while cutting watermelons with a kitchen knife. It's quite hard to pull out.
- For mat-cutting the grooves might catch the fibres and throw the cut off, unless your alignment is absolutely perfect. That's probably why it's less ideal, but that won't apply to combat in the same way.
- When it comes to thrusting I don't think the grooves make that much of a difference. Your main target would be the torso, which is not a solid block of meat, but mostly hollow, with air-filled lungs and organs that can be moved. More likely, the blade might get stuck between the ribs/bones or the blade might bend when a body slumps over. Grooves won't change that.
- weight reduction/distribution seems the most likely reason (at least it is for western "fullers"), although I'm willing to concede, that the exact form and nature of the groove in question will dictate the purpose.
I always assumed the _hi_ (or similar pieces) was almost purely decorative. I would buy the weight argument, though. As another martial artist pointed out, “you were wearing or carrying your weapon far more often than actually using it”.
Hi Shogo! I've been a fan watching your videos for just over a year now, and I just wanted to say that of all the awesome TH-camrs I watch, whether the topic is historical, cultural, music related or healthcare (my field of work), you have the absolute best introduction of them all, with your greeting and bow! And I love all your videos, the way you typically structure them is so great. And they're very informative - hopefully I will find them especially useful when I can finally visit Japan, such as etiquette and all the cool places that a visitor should not miss out on. Doumo arigatou!
The groove is for a vacuum break not only to remove from saya or scabbard and also when cutting through flesh.
Some of my kitchen knives have grooves that help when cutting.
Just yesterday I was cutting a watermelon with a chef's knife without grooves and the blade got stuck in the flesh of the watermelon.
Love your videos.... maybe try and physically show the difference of a blade with and without a Hi? That would be a great video.
I also questioned about the real purpose of the groove on the katana. I found the main purpose of the groove is for quick drawing after a stab in a bloody battle. Like other weapons with a groove, the air coming through the groove help users to draw the sword out of the wound easier. In addition, the sword would absorb a strong impact if it hit a hard object/ another sword. The groove with a week thin layer of metal could absorb the impact from the hard front blade to the soft metal on the groove. It would keep the blade not broken. For all of those reasons, why the groove would go all the way along the blade is another question that I am looking for an answer.
On some knives, the grooves are only for optical purposes. There is also the aspect of moving mass from the center line outwards, allowing for a thicker or wider blade, increasing the torsion resistance while keeping the mass of the weapon the same. The point of making it easier to pull the blade out after stabbing seems legit - you could try that on a nice pork side and turn it into teppan yaki afterwards :-)
And then there is the fact that humans are creatures of habit, maybe the grooves had a reason to be there on older blades, and they have just been copied without a real reason but because bladesmith - now and then - believed to know things that were effectively not true but nobody noticed.
I believe it is use to prevent the blade from getting stuck when cutting, having a groove will make sure air can flow thru while cutting.
All due respect, Shogo, everything I've found points to the simple answer of reducing weight while maintaining most of the structural integrity/rigidity. Nothing to do with stabbing as the earliest blades with grooves tended to be wide bladed cutting swords very often with rounded tips.
As a chef, A granton edge or scalloped knife is excellent for slicing and stopping stuff getting stuck.
I'm learning about scalloped knives in culinary school. Heard, Chef 👨🏻🍳🙋🏻♂️, and seconded. 🔪
I think people choose or avoid it for any of the said reasons.
All the time I always thought to myself: "What if once someone just created a Hi as a decorative element of his blade, because he wanted a simple, but nice looking decoration, and others liked it and wanted one too? Maybe the question for the use of it came much later?"
I know that historical weapons are often simple and their Parts for a reason, but such a grove is in my eyes, the simplest way to decorate a weapon without puting it off balance like a decorative pommel, uneaven Guards or complex engravings cold do.
This was interesting!
Thank You!
You are correct 100 %.
The grooves are made by using a "pinching" tool while the metal is hot. This isn't a matter of removing steel. Therefore, it removes NO weight at all. The shape does (as you mentioned) create a stronger structure at the spine of the blade. It was the practice to cover the spine with clay before quenching. This hardened the cutting edge while giving the spine a softer temper. This allowed the blade to bend rater than break when striking a surface with force.
So no, the pinching process removed NO weight from the blade.
I think if we are talking about an actual sword used to kill in combat, the benefit of the Hi would be what Shogo said, it creates less friction, this also applies to Batoujutsu (sp?) , where you attack by pulling your sword from the sheath quickly as part of the swing. I guess the other commenters are only thinking in terms of Western weapons, or they are thinking more along the lines of a decorative sword that's mainly used for practice and ceremony, where the weight would be of a higher importance. I think the bigger improvement comes with the lack of friction. However, like Shogo also said, it probably depends on what you want to use your sword for as to whether or not you want one with a Hi or not.
Less weight means faster swinging, faster reaction, less tiring.
Those are very important attributes in combat. Independently of the culture.
I never would have guessed
This is the first non short I've seen from Shogo
I feel like Shogo should make a podcast
Bro your content makes learning about this stuff so entertaining and makes me wanna watch more keep it up👑😁
Thank you very much, Shogo - for this interesting video !
You keep asking me to play at 1.25 or 1.5 speed but the way you speak actually helps me pay attention and the more time I spend on your video the more money you get
Still watching, but from watching Forged In Fire I thought it was a fuller to make it lighter yet strong at a significant length.
I believe this is the correct answer. I have done some bladesmithing in the past and adding a fuller is designed to reduce the overall weight of the blade.
It is likely but lets not jump to conclusions
First of all this is a katana not a longsword, it might be different, i dont think any of us here know
And in longswords the fuller is also added to be able to make the two edges more acute, not only for weight reduction. On a katana there is only one edge, idk how this makes the "fuller"'s purpose different
Again yall might be right that its to reduce weight but i think we need to do more research
@@idkwhatthisisforplzhelp3678 Fullers are commonly added to many styles of knives, daggers and short swords which negates your point about the longswords. The above examples also may have 1 edge like bowies and bayonets blades.
@@DrIgnacious negates my point what?
My point was we dont know crap about katanas so we shouldnt just assume and instead research
Thank you so much, I’ve learned so much about katana’s, it’s so fun to learn about all the different parts and how to handle it 🤩
The muscles will spasm around the blade making it difficult to withdraw. Twisting the blade allows the Hi to break the suction and get your sword back for the next ninja.
It’s purpose may also be to make it easier to sheathe the sword without looking, because you feel with your finger when the Hi ends, so you can look around if you missed some enemies or other threats
I used to see katanas like a cool iron stick-sword.
But after watching these you can see that how much people thought on a sword just to make it more usefull
I thought the groove on the katana was to guide the fingers and the blade when sheathing, so we can sheath the katana without even looking at the blade and the sheathe
Here's an idea, the groove puts the center of gravity closer to the blade edge which gives you more precise control over it's angle and position.
I like the idea, but I've used swords with and without - there's no real difference in feel while swinging. The curve shape and length, blade shape, and handle + tsuba do have a great effect on that feeling.
@@derikduley7806 The weight of a blade is just as much a contributing factor when it comes to balance and weight distribution. It does make a difference even though it's not the only factor.
As usual, very interesting.
Shogo thank for your videos, I agree with you, when a sword or long blade is stabbed it is difficult to put out, so the Hi, help remove the blade. Thanks again, Sayonara!
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I thought it was for easier keeping in the sheath, or drawing it out smoother.
Learned alot throughout this video. :D
The groove in a sword seems to have two main purposes: to reduce the weight and to increase the strength. A large groove can reduce the weight by 30%. But it also has the function of stiffening the blade (especially when used with proper heat treatments). A blade with a groove will not bend laterally so easily (since it becomes like an "I-beam"), so it becomes much stiffer and therefore more deadly (when used by an expert). A grooved blade is a much more deadly weapon than one without a groove, because it can respond much faster to any input and it maintains its own integrity much better (being a much stiffer blade).
Stiffness is not increased, it's merely retained. After all, material has been removed so it can't become stronger. You'd have to change the overall geometry to achieve that. For example by creating a T-shape to increase lateral strength. That has its own downsides though.
@@youtubevoice1050 It does become stronger and stiffer because it becomes like an i-beam. The H-beam and i-beam are common engineering standards in construction because they are stronger and stiffer. That is just applied science.
@@nicholasbishop5892 It does not "become stiffer", because you're not adding a lateral reinforcement, you're merely removing material in a way that does not compromise structural integrity. That is a common misconception. An H-beam isn't stronger than a full beam.
You can obviously forge the blade in a way to be stiffer BY including a fuller and leaving MORE material at either side of it, but you cannot reinforce an existing structure by removing material.
In katanas I don't see the geometry being changed. If the spine of the blade was turned into a T-shape (called pipe-back in the west), then yes, it would be stiffer than a regular katana. But that is not the case here.
@@youtubevoice1050 There is a "relative" increase in stiffness, because we remove 20% of material but maintain the original stiffness (the same as it was before), if the fuller groove is properly made. That gives the lighter blade a much more effective response and action. That weapon is much more deadly than without a fuller groove.
What you said about the likelihood of remaining calm enough to hold your sword parallel or downward got me wondering if maybe those stances where originally developed for the tachi or even odaichi, in historical European martial arts the only time I've seen swords held that way is with long swords and bigger, which tachi where right around the same length as European longswords.
a tachi is a katana
I don't think staying calm during a real fight was an issue. Most of the people using them surely were used to fighting and death. And yes, I also thought about those stances where you would have a sward in a "downward" position.
As for stabbing, I remember some bits from European history that made an argument that the reason why the Roman empire was more successful on the battlefield than other nations at that time, was because the Romans preferred to make stabbing moves over slashing moves, and the mortality rates were higher with stabbing wounds over the slashing ones. So 'hi' being used to make it easier to pull the sword out, seems very natural to me.
I think it might be a bit of a combination with some of those ideas in mind. And probably largely, simply because it's traditional and very aesthetic.
Saw this elsewhere in the comments but I have to say it again. The groove is for structural integrity. It redirects force along the length of the blade rather than perpendicular which could cause it to bend or break. This is an engineering basic to redirect force in a direction that the structure can handle. Any other reason simply does not have enough of an effect to warrant the design being so widespread.
Have to mention a basic experiment to test. Grab a normal piece of paper by the bottom edges and stand it up. It will most likely bend in the center and slump over. Now fold a groove in it. The paper will stand up straight without issue. The force is redirected in a straight path from the top to the bottom rather than wherever force is applied.
Great video more please about nihonto ettiquette, parts, maufacture etc awesome work shogo
The perpose is to reduce weight. It's the same among all swords from any region that possess a fuller or groove. The releasing the vacuum thing is a myth and the increased air resistance is negligible compared to the difference in weight. Humans are squishy and wet on the inside. So the only thing that would make it difficult to pull out is if it's stuck in bone or cartilage and a groove won't help with that.
I never thought that my undying live for a video game, Ghost of Tsushima, would lead me to learning about Japanese culture and owning a newfound respect for the Samurai.
I am agree with the hi groove is for make easier when they pull the sword from the enemy body, but i rarely see a jutsu or kata their main attack only thurst the most i see a weapon with it in spear.
From my understanding the hi sometimes is made to correct the smithing of a blade. When a blade is heat treated sometimes the steel cracks and weakens the blade. So the bladesmith can remove and correct a crack by grinding it away. I'm not sure if, when corrected, it is done on both the omote and ura side of the blade, or just one side.
I always thought of it as a vacuum break when and if the sword was lodged in a body. The hi allowed the sword to be removed more easily.
The katana, small as it is, is almost the same weight as a much larger longsword. Fullers not only reduce weight but increase structural strength.
katanas can be crazy long or the size of a knife.
Again a lesson learned! Thanks!
The fuller can also affect the path of the blade and the edge alignment of the blade while it is traveling through the targets.
Shogo - you rock sir!
My general understanding about the groove/ hi/fuller is that it helps strengthen the blade and lighten the sword.
the argument that a fuller is made to make the blade easier to pull out ist widely considered to be an urban myth.
there is so much people in the comments talking about weight, but the inportant thing is the point of balance. A rapier is heavier than an arming sword but much more nimble because the point of balance is closer to the hilt. And of course the fuller if it's grinded is to reduce the weight and if it's forged to wider the blade or aesthetic.
I've always believed that grooves are to break the natural suction created between sword and wound. trying to remove a sword after stabbing is very difficult if the seal is perfect (ie no groove)
The body, especially the torso, is not a homogeneous block of meat though. So the resistance is smaller than you think. The blade might rather get jammed between bones, in which case the grooves won't help.
The hi or fuller is used to help the blade handle stress when you hit something with it.
It's still weaker with the fuller than without so how is being weaker gonna handle stress better?
I feel the concept of making it easier to pull out would make sense for anyone on horseback who might not have as great of leverage.
I disagree. I think it has more to do with integrity. Most blacksmiths I've heard ever mentioning fuller say they increase the durability and integrity of the blade. A fuller will generally make the blade stronger and stiffer. There is foreign weapons with fuller that do not have tips for stabbing or thrusting. While it is possible that weapons and cultures could have fuller for different intentions I would think that the fuller is most likely not only passed down technology but also convergent evolved technology. Cultures around the world most likely noticed these properties so generally the reasoning should be similar in most cases.
Thank you for someone who realizes that a groove improves structural stability. Try and stand a piece of paper up on its side it bends in half. Now fold a groove in it and do the same. The groove redirects force along the length of the blade rather than perpendicular to it.
Engineering Fact.
I always thought it made it easier to cut with since it'll have less friction, like with European swords having multiple fuller lines it makes it's dimond shape flatter and have less resistance when passing through something
Hey Shogo, I would like you to make a video where you show us the dojo you study iaido at and introduce us to your sensei.
Hi (樋)is not Grooves (溝)but gutter (樋)in Japanese. Hi is the Japanese word for liquid drainage equipment.
You can find the explanation by searching the words katana(刀) and hi (樋)in Japanese.
"The muscles that receive a strong impact contract. The contracted muscles stick to the blade like a sucker. By letting air out of the Hi , you can pull out the blade from the muscles that stick like a sucker. "
In the story of a samurai, an immature samurai stabs katana deep into the enemy's body,However, since it is difficult to pull out katana from the body, there is a scene where the samurai is in a hurry when he sees the next enemy.
"Get in to the groove, sword, you got to prove your blade to me.... yeah "
Fullers on western double edged blades can reduce the weight of the sword by up to 35%, and since it creates a near i-beam like cross section does so with extremely minimal compromises to integrity.
Can we have a moment of silence for all the people Shogo practised on to test his theory
In regards to the durability, I think that depends on how the grove is made. If it is made by removing metal from the blade, I can see how durability would be a concern. But if it's made during the forging process by putting a metal rod over the heated metal and hammering in the grove, then the metal would be compressed and should actually be stronger in the grove. But I'm not a bladesmith and just offering a thought. I have seen a program on the History channel called Forged in Fire where they actually create blades and even try to recreate blades from history.
Can you talk about repairs to a katana and maintenance for deep rusted Katanas please!
I love japanese sword or samurai. I hope someday i have that kind of samurai
Well, grooves ARE made to reduce the weight, this is well-known fact
Strongly curved sabers, for example, can't have grooves for easier pull after stab, because you can't stab with such curved blade
European sabers can be used for stabbing as well as cutting. The long, heavily curved sabers popular with ancient middle-eastern cultures, however, could not. Those particular swords had long, delicate bodies and angled handles that made it extremely difficult to thrust, nevermind the issue of structural integrity.
its a fuller used to remove weight and in some cases it can strengthen the blade
I always understood the channel in a blade was to break the surface tension in the meat.
Making it easier to remove the blade.
But if you just hang your blades on a wall and not use them I can see the mystery
Always thought it was too make the blade lighter, but I'm just repeating what I heard by others.
To keep oil in when fighting mons- Wait. No. Forget it. I'm not Geralt of Rivia.
I always wondered why swords in general had groves, and tbh I always assumed they were just cosmetic. The true function was... A lot more grim than expected...
2:11 minute in. I think the Hi is for making the katana back stronger. I dont know, it just came on my mind.
Shogo, I have followed you for a while now. You have inspired the creation of my own channel devoted to Iaido and my perspectives on the art. I have not added any content yet because of some health challenges, but that will be coming. I also listen to your podcasts, the latest of which has the comments turned off. I am an academic with a Doctorate of Business Administration. I specialize in technology and innovation management. As part of my research, I study leadership and leadership theory. Acknowledging the strong potential for culturally-based intervening variables, I have some thoughts about leadership you might find useful I could share with you privately if you would like.
The Hi groove has exactly the same use as the groove of european longswords (eu sword in general) : unstabbing. To reduce the weight, there were other techniques used during swordsmithing like drilling a tunnel inside the blade at each side of the tang making it lighter and harder to break
I personally use the hi as a guide when I noto
It’s a weight reduction method I and those are very difficult to get correct when forging the blade so many have gone home on forged in fire cause they didn’t get those right or they got too deep with them and compromised the integrity of the blade
Did he mention reducing the overall weight? Consider the groove as Roman engineering of an arched tunnel. Why is an arch 'strong'. The blade has the strength of a much heavier blade with a thicker spine, while lighter because an 'arch' supplies the lateral strength which is the vulnerable direction for bending and snapping.
It's slightly amusing that there is similar controversy regarding the purpose of fullers on some western swords.
There WAS. It's CURRENTLY largely settled for anyone who's not new to the topic.
@@NieroshaiTheSable :) Depends who you ask.
It actually widely agreed in european swordsmanship that weight reduction and mass redistribution is the reason you put fullers in blades. This is very well known in a lot of european blades, especially apparant in those of the military era.
🤔 About the hi making it easier to pull out the sword after stabbing. The problem i have with this theory is that rapiers for example were thrust centric swords and they had no fullers. Can anyone with more expertise than me explain that?
The fuller is all about weight. There is no way that the speed advantage of a 10% lighter blade could possibly be countered by "air resistance." Some blades would be unusable w/o their fuller design, not to mention that using less steel is economical (especially in historical periods).
I don't know any katana smiths, but smithing is smithing and metal is metal.
Shogo, when and whom started putting the Hi on the sword? I have always thought it was to allow air to flow and allow you to pull the sword out of a stab wound.
The reason a skilled swordsman would eschew a Hi is that the Hi makes it easy for a sword to ‘swoosh’ where as a skilled swordsman can move his sword swiftly enough to ‘swoosh’ without a beginner’s aid.
I thought it was to make the blade less bendy, like a modern I-beam.
Can we compare the concept of the need for the hi in a blade, to having two strings on a shamisen instead of three? As in, the shamisen can do its job with two strings, but it can't have the same function as one with three strings. And a sword doesn't have the same air resistance without a hi, but a sword doesn't at all need a hi. Thanks Shogo.
I think only one of the above. To lighten the blades and balance the blade. Noise is a modern construct. I doubt a samurai wanted their enemy to hear it coming.
I think the last thing on my mind is that my sword is going to rust, I'm too busy trying to stay alive just to survive the fight. Steel don't rust quickly, death is certain.