Why Grooves on Katana?

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Let's ask Shogo | Your Japanese friend in Kyoto

19 күн бұрын

Ever wondered why there are grooves on the blade? In Japanese, they are called Hi or Bōhi, and there are various reasons and theories for why katana have them. First, it’s to make the blade lighter. A katana with a Hi is 10% lighter than those without. Second, it makes the swinging sound bigger. A katana without the Hi does make a sound too, but it’s not as big and clear. Third, it makes it easier to pull the blade out after a thrust. Like kitchen knives with holes don’t get the ingredients stuck to the blade, the Hi makes the blade easier to remove from the opponent’s body after a thrust. What other theories do you know? Please let me know in the comments.
*The content is based on personal studies and experience
There is no intention of denying other theories and cultural aspects
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Пікірлер: 138

@endikaaspeurrutia1013 17 күн бұрын

10% less weight doesn't sound a lot but when you have to use that thing for a loooong time 10% less is a lot

@SkyTowerKurogane 17 күн бұрын

Also at the speed you're swinging it, that 100 grams aren't going to feel like 100 but 300 or more.

@Sbudz 17 күн бұрын

10% less weight only sounds like a small amount to people who don't know what they're talking about. Not tryna be a dick that's just fact

@VikingTeddy 17 күн бұрын

Also, the thing about it being easier to pull out of a body is a myth. I kind of expected Shogo to know that.

@antiheld7323 16 күн бұрын

@@VikingTeddy why is that a myth?

@mabolzichjjl 17 күн бұрын

It adds dimension to the blade making it less prone to bending, too

@Sakata-gd9lu 14 күн бұрын

Actually with traditional nihonto. Having the bohi often makes it less resilient to bending. With modern monosteels that aren't differently hardened it's not an issue though

@ronsorage78 17 күн бұрын

In western swords its called a fuller and its primarily for reducing weight.

@willplume1555 14 күн бұрын

And adding structure and resilience.

@rejectionrole1237 2 күн бұрын

@@willplume1555Adding structure and resilience was always the primary purpose. The lighter weight was a benefit.

@milliont123 17 күн бұрын

I always thought it was for structural strength in the blade to better absorb shock and prevent it from being damaged as easily

@Wirrn 16 күн бұрын

Its not so much the groove makes it stronger as the groove allows you to make it thicker (and thus stronger) without making it too heavy

@TheSteam02 17 күн бұрын

Just gonna say this for the record: Blades with a fuller/bohi are not easier to pull out of a body.

@nathanielburns6692 17 күн бұрын

Uh.... why.... why do you know that

@TheSteam02 17 күн бұрын

@@nathanielburns6692 1. I watch a lot of sword KZfaqrs. 2. I invoke the 5th

@Nityum 17 күн бұрын

bohi is not practical for fighting or cutting its only suitable for iaito or practice katana

@TheSteam02 17 күн бұрын

@@Nityum If you've seen any historical sword in museums with battle damage, you'd realize that many of them have fullers. Fullers absolutely serve a purpose. The 10% weight reduction is noticeable.

@pierredunn68 17 күн бұрын

@@TheSteam02they are also sometimes added to make the blade more rigid, but i don't think katanas need that, they are quite fat and rigid unlike the european swords that bend and flex quite freely. I feel like the weight reduction is the one and only intended purpose for the bohi, everything else is coincidental

@someperson7 17 күн бұрын

It's because Katanas are groovy

@arkadandfortuna1582 17 күн бұрын

I also used to use it as a guide for my thumb during Soete-tsuki 😂

@edbangor9163 16 күн бұрын

A hi is a type of fuller. There's little evidence to say that they make it easier to pull back after thrusting the blade into something, but they do reduce weight. And if the fullers are forged into the blade, they can actually increase its stiffness

@borttorbbq2556 16 күн бұрын

The Japanese one is a lot thinner and deeper so it actually does create an a pocket that theoretically might help quite a bit though I have a feeling it would open up a slash wound a lot easier

@hollundergiersch8691 17 күн бұрын

If the Hi is made with a Hammer and not with a grinder, it makes the blade more durable, due to its geometrie

@zanshin09 17 күн бұрын

On Nihonto they're made with a drawknife.

@charleshurst1015 17 күн бұрын

I always assumed it was to make it lighter

@xdragon2k 17 күн бұрын

While keeping the structural rigidity of the sword.

@andrewrussell1678 17 күн бұрын

strengthening as in corrugated cardboard etc-engineering!

@YourHandleHere84 17 күн бұрын

Shogo-sensei, I thought the bohi was just the Japanese term for a fuller, which is used to reduced weight without significantly reducing strength and stiffness. Is this incorrect?

@zanshin09 17 күн бұрын

This is correct, and it's first (and most important) reason he listed.

@leniterfortis4832 17 күн бұрын

Theory: It looks cool

@sirderik 16 күн бұрын

I have one theroy.... Water/oil To main a blade especially back in the day you would use oils....maybe the grove is there to help with that... And water... Well it gives a nice path for rain water if you have too sheeth inside a wet or moist climate so you don't get water damages on the blade as easily...but I am just guessing.

@devin5201 17 күн бұрын

The thrust thing is a bit of a myth, one has to remember that flesh is squishy and expands to fill spaces so the groove would not create the air pocket that proponents of this idea tend to speak of.

@JD-gn6du 14 күн бұрын

In western blade smithing it’s known as a fuller, it allows for lightning of the blade while adding strength.

@Stonehedged 17 күн бұрын

Its also a flex for the swordmaker

@0ddBall7704 17 күн бұрын

Absolutely! For a long time I was a big NO BOHI! Until that fateful day, it was embarrassing, everyone was looking at me and it was stuck.😣😢 I had to put my foot on his chest, truly embarrassing. Now, I never leave home without a BOHI. 😊

@Advokitt 15 күн бұрын

I always assumed it had to do with providing a channel for air to evacuate when the sword is sheathed, preventing trapped air from pushing the blade back out.

@lucashenry6281 17 күн бұрын

It’s a better way to relieve stress on the blade during fighting. Those groves remove metal which allows the blade to flex just a little bit more.

@YourHandleHere84 17 күн бұрын

What are you basing that statement on?

@lucashenry6281 17 күн бұрын

@@YourHandleHere84 historical blade design. Why do you think European swords have that same groove? Remember, physics doesn’t change from culture to culture.

@LSWoOz 17 күн бұрын

@@lucashenry6281to remove weight, source I'm a blacksmith, a fuller doesn't help it flex much at all. The type of steel has a much bigger effect than a fuller ever will.

@lucashenry6281 17 күн бұрын

@@LSWoOz I’m a gunsmith, fullers still remove weight and NO INFANTRYMAN HAS EVER WANTED MORE WEIGHT. So even if the fuller removes a small amount of weight from the sword, it’s still worth the effort. Trust me on this, as someone who also happens to have taken multiple hikes with their 16 pound hunting rifle, I’d take a fluted barrel every day of the week. (Don’t ask why I haven’t fixed it, I’m kinda masochistic like that)

@SuperFizzah 17 күн бұрын

@@lucashenry6281what does any of what you just said about weight have to do with the ability to flex, like you originally claimed? Maybe I can't read, but the person you responded to actually agreed about the weight saving aspect and then disagreed about a fuller or bohi doing anything to help with flex? He's right too, a bohi doesn't add or reduce any amount of flex...

@joenoble5469 14 күн бұрын

The 10% lighter thing is not a theory. That is standard practice in blacksmithing to put a Fuller (groove in the blade) to reduce weight.

@KazeOrion 9 күн бұрын

So interesting!! I could listen to you talk about swords all day Shogo-dono! 😯☺️

@SwedishSinologyNerd 15 күн бұрын

That's easy. It's to make your swings more... groOoOovey, dawg xD

@eddyheyrick7170 12 күн бұрын

The fuller has the same function as an H-beam. It ads to the strength and stability of the blade. Easier to pull out after a trust is a myth with no historical context.

@hexenex 9 күн бұрын

Your reasons are entirely correct. A grooved blade, for as odd it could seem, is also structurally stronger. Like an "I" steel beam in a building. And that goes with the need to make it lighter without weakening her.

@Celestial2107 14 күн бұрын

If I remember correctly, the English used to have such grooves in their swords for knights when they had thrusting swords for horses. It helped with ease of use if I remember correctly

@danevalnes6129 17 күн бұрын

My sensei says that the hi making it easier to pull out is made up. The first two reasons you gave are correct tho. Weight being the main reason.

@stringchz 17 күн бұрын

Did your sensei explain why? I'm just curious because the bohi doesn't generally span the entire length of the sword. If you stab it through something, there's a few inches before the bohi makes contact, which would create a sort of release from the surrounding pressure. At least, that's how it works in my head but I'm no physics professor!

@devin5201 17 күн бұрын

@@stringchz proponents of the idea say the fuller creates a space of air breaking the seal around the blade made by the flesh, but flesh is squishy and maleable, and has a tendency to expand a little and fill spaces.

@devin5201 17 күн бұрын

PD. Fuller is just a more general term for such grooves on swords.

@borttorbbq2556 16 күн бұрын

Okay so basically when you're talking about a blade getting stuck in soft tissue only which can happen generally it could help with that but most times your blade is stuck because it's literally stuck in bone and if you don't have time to remove it correctly it can be a b**** to get back out

@borttorbbq2556 16 күн бұрын

@@devin5201the Fuller is the Western name for the groove in a blade. You are just using it as a general term

@jamuguerza 13 күн бұрын

I think the use of grooves was a common inowledge of most of blacksmiths all over the world, because they were commonly used in western blades as well.

@Patrick2345454 15 күн бұрын

It's purpose was to lighten and stiffen the blade. Any unnecessary material was removed, and it would be harder to bend or snap a blade without that extra weight at the end, if you struck too far down the blade.

@seara-tears 15 күн бұрын

i believe it makes it easier for swings and movements when avoiding an opponent.

@jaden009 13 күн бұрын

It also means it uses less material. And since making steel for a katana was long and complicated, it saved resources.

@xxmpcxx 9 күн бұрын

Easier to pull out after thrust, got it👍

@althesmith 17 күн бұрын

Reduce weight while keeping most of the rigidity, same as swords everywhere. The thrusting thing is a bit of a myth- most dedicated thrusting swords had no fullers.

@complexion235 17 күн бұрын

im pretty sure the sole reason is to make the blade less bendy. like when you curve a piece of paper it will suppourt itself under its own weight.

@Gutu-pd4xr 17 күн бұрын

I just assumed it's too make it look cool. And it works.

@danielbob6900 17 күн бұрын

Increased structural strength plus the three that you stated earlier.

@kogamanjitani6733 16 күн бұрын

I've heard from my master that the blade allow air to inter the enemy's buddy after stabbing.. making the attack more fatal..

@r1pbuck 15 күн бұрын

It's a method for adjusting a blade's balance, among other things.

@crimsonzone8984 7 күн бұрын

Can you guys make a video about double bladed swords?

@greyvr4336 16 күн бұрын

A friend and I are very curious to learn how long fullers have been used on Japanese swords. I got to see one from the 1300s with them at the Tokyo national museum, but were they present even earlier?

@ulimuller8830 15 күн бұрын

Faltaría valorar como influye en la fabricación tradicional de la hoja en especial el tratamiento térmico de templado 😮

@quenula 16 күн бұрын

Thank you for a lot of great videos! Is that a dotanuki blade? It looks wider than "normal"? Is it possible to buy in that configuration?

@dustfang5422 16 күн бұрын

It stiffens the blade as well, so you don't need as much steel, the blade can be thinner. European swords use them too, there, it's called a fuller.

@kb4866 17 күн бұрын

A swordsmith told me, that it’s for a better balance

@carterjoel8467 15 күн бұрын

After a thrust I thought you wasn't supposed to stab

@TeutonicRoom 17 күн бұрын

Edge retention is one that I have heard.

@pyrodude5119 17 күн бұрын

I think this Katana is longer, wider and bigger than your average Katana.

@borttorbbq2556 16 күн бұрын

I mean it is analogous to the Western Fuller. But overall they basically do the same thing also it will open a wound on a slash even more than a blade that doesn't

@michaelpettersson4919 16 күн бұрын

I have never noticed those groves on katanas before. It is possible that I never reflected on them. I do however know that European swords tend to have them as well. Probably of the same reason. I just looked on a bunch pictures of katanas. Some have the grove and others are lacking them.

@SamSpeed90 8 күн бұрын

The grove doesn’t help with the pulling out of the blade after a stab. That is a myth as far as I know. Case in point, a Gladius, a Roman sword, didn’t have the fuller and didn’t have any issues being pulled out of bodies after being thrusted in them.

@staytoughbarkmellowman 13 күн бұрын

The heat makes the plate easier to move from the opponents body after a thrust is something I really wouldn't know about because I'm probably already a blurred vision flinstoning away after saying *you win* before that even happened. *Poof Gone*💨

@pinkdlophin9337 16 күн бұрын

It reduces weight and gives structural strength.

@CallanElliott 14 күн бұрын

A hi is called a fuller in English, and it's to make the blade lighter without compromising strength.

@dapperdog2719 15 күн бұрын

It also makes it stronger

@robertsprague5440 17 күн бұрын

Is it possible to also add strength the the blade

@RachelGohlman 16 күн бұрын

No one wants bits of the other guy stuck on their blade.

@banditch4769 17 күн бұрын

Have you ever did a video on naginatas/yari polearms?

@navoJ 14 күн бұрын

i think its way katanas are forged and cooled

@deltasource56 15 күн бұрын

Faster to draw since it's not vapor locked in the scabbard

@teddgrizz2338 16 күн бұрын

Is there any iaito with bo-hi? And is what you're holding an iaito or an actual live blade?

@MrAqr2598 17 күн бұрын

btw grooves on swords are technically called "fullers".

@WeirderWeirdoo 17 күн бұрын

Doesn't it also make it harder the bend the blade's flat side?

@kyleeames8229 17 күн бұрын

So they’re called bōhi. I actually tried to look that up by searching for a translation of “fuller” to Japanese. In addition to being the superlative form of “full” it’s also the English word for hi. No luck. Finding translations of specialized terminology to other languages is one of the most frustrating things about learning. That, and the hesitancy of native speakers to correct mistakes from fear of offending. 習いたいだけ。間違えてるなら、教えてください。

@rolandgdean 11 күн бұрын

I always heard that called a "blood let" because it "lets the blood" flow past the blade so that the blade doesn't plug its own hole completely. Also lighter and won't get stuck inside your enemy. The Roman gladius had them for that purpose because their main attack was to thrust and stab in close quarters.

@elvondrago96 15 күн бұрын

Aerodynamics adn Physics applied on that type of sword.

@ObservationofLimits 17 күн бұрын

Most grooves on swords are lightening and gives it spinal support

@circeciernova1712 17 күн бұрын

For fun (:

@Taison77 15 күн бұрын

Reduces the cost of materials. You're using less per blade.

@m.f.1132 9 күн бұрын

i think its like in a european sword to make it strucktually stronger and more riged

@alterego3045 10 күн бұрын

Как и на ножах, для воздушного удара

@Thesamurai62735 17 күн бұрын

Cool

@eugeniaq8875 17 күн бұрын

It makes the blade easier to remove from your opponent's body. How often have you done this? 😂

@theamazinghaole2384 13 күн бұрын

TLDR: Makes killing sound cooler and easier.

@ltw6888 16 күн бұрын

“the ingredients”

@danielemmanuel6261 15 күн бұрын

Sword go big woosh

@ko3esirene 13 күн бұрын

Because when you made 100 you can produce one more for free

@LetsaskShogo 12 күн бұрын

🤣

@isi3012 17 күн бұрын

Why had some Sayas animal fur on them? Was it to protect the original Saya-case, or was it some fashion-style thing?

@BrumEldar 17 күн бұрын

to protect from the rain

@PheonixAA 10 күн бұрын

Why you touching the katana 😅

@tautuaom 16 күн бұрын

Does he have anyone that does yuri techniques?

@justachievements1974 17 күн бұрын

❤

@mate16031 17 күн бұрын

I thought that the katanas that samurai used were for slashing and not for thrusting, unlike the ninjas katana

@poffuz1 17 күн бұрын

They used it for both. Stabbing and slicing.

@mate16031 17 күн бұрын

@@poffuz1 but it was made for slicing only cuz of the end of the blade

@devin5201 16 күн бұрын

Unless the blade is very very strongly curved it will pretty much always be at least decent at thrusting since humans are pretty darn squishy and you only need a few inches of penetration to touch organs. Okay SOME swords have blunted tips but we're talking about katanas right now.

@GreekShinobi223 17 күн бұрын

Doesn't "hi" mean fire though?

@zanshin09 17 күн бұрын

Yes, but this is a totally different word, it just sounds the same.

@residentevilumbrella2001 17 күн бұрын

I own 7 katana and ninja swords and I made sure that when I ordered them that they didn't have those wavy grooves. Perfectly straight and smooth.

@Larper64 17 күн бұрын

The wavey edge isn't the groove he is talking about, the hi is near the back of thr blade. The wavy pattern is called the hamon, and despite resembling a groove or serration is often nearly smooth. Not sure why you would actively avoid having hamon but to each their own.

@kenseiden1 17 күн бұрын

Yes, designed to ease the withdrawal of the katana from a bleeding body by allowing an air gap between the flesh otherwise causing a suction effect

@Valdyr_Hrafn 17 күн бұрын

I've heard the "easier to pull out" theory being debunked on account that the difference between those surfaces have very small to neglegible effect. A big advantage to it is the way it makes the sword way lighter without compromising its strength

@adam_y_154 17 күн бұрын

my theory : katana is OVERRATED.

@stringchz 17 күн бұрын

The anime weebs would like a word with you.

@YourHandleHere84 17 күн бұрын

I’m no weeb, but I do like the katana best. I own a traditionally made katana (high-end Hanwei, so not a true nihonto, but still folded, differentially tempered, etc.) as well as a traditionally made English arming sword (from Tod Cutler), and the katana is vastly more comfortable to wield/move around, and honestly it feels more natural to hold. But both kinds have their merits and purposes based on when and where they were first crafted, and I believe that can be said for all types of swords.