Why swords have a fuller, part 1

Why do swords have fullers? Well in this video I clear up the misconceptions!
Matthew's channel with some great sword reviews: / krunan

[@MrMicroMan1]

Some "historian" came to my school and brought a sword with him, and asked my class why it had a groove, I said it was mainly to reduce weight, he laughed at me and said it was a blood groove. As someone that is interested in swords, I spent a good 30 mins arguing with him after class was done. In the end he just smiled and ignored me....just thought I would like to shared this with people :')

[@MrMicroMan1]

+AuthenticNaabi sorry this was last year and unfortunately I couldn't remember his name :(

[@DimmVargr]

It's sad when you realise this story accurately represents the knowledge level of _most_ teachers and other 'specialists' in schools :(

[@John-sz7vf]

Sad thing is, people will believe him over you because "He's an expert"

[@xllab1]

TacDyne There are much more lies than this and on much more important subjects. One of them being the number of people that died because of the "Holyghost". They want white people to feel ashamed and to allow them to rule the world.

[@janbadinski7126]

People who lack confidence are of the mindset that no one can do any better than they can. It's good that you know the facts instead of being a poser like him.

[@bengrogan9710]

+I Am Shad as someone who does engineering I'd like to point out a few things that I believe you have missed as to the purpose of the Fuller. I hope you see this and find it useful. 1st I am not arguing that a fuller would strengthen the transverse torsion resistance (Bending resistance) of a blade, it is self evident that that is true. However there is a factual strengths advantage to the fuller which I will try to explain. The Fuller is not material that is removed, it is a swaiged line in the core of the blade this means the material in the core of the blade is compressed and pushed outwards, this is important as it removes material from the "Core" of the blade and extrudes it from centre. When you strike with the edge of a blade you apply 2 sets of forces rotationally at the point of impact, on the striking side on the blade you are compressing the blades edge, on the reverse you are applying a stretching or tensile force. To demonstrate this in a way that is easy to visualize, roll a sheet of paper and hit something with it. You will see that the paper will continue forwards at the tip due to momentum, wile it stops at the impact point making the paper roll crease and collapse forward. The back of the paper has stretched and the front has been compressed as folded over. In the centre of a blade these forces are in balance, as I said the front is compressed, rear is stretched, the centre is a transition between these two and has a far lessened stress. The metal extruded by the swaige of the fuller means that metal is moved from the centre where forces are low slightly further from the centre meaning that the force is applied to more mass, reducing the effect. Now you may be thinking that that isn't an issue for swords but it is, and I'll try explain why next. 1st you need to understand when stress fractures occur, they always appear at 90 degrees to the point of load and that metal has some aspect of elasticity When in combat, if you where to strike edge to edge on a blade they will bite into one another creating a bite mark. This is very dangerous as when you strike, that bite is now a stress raiser. The natural elasticity of the metal means that it will stretch to some extent and return to its original form, when stretched hard it will deform and bend and finally if the bending force is too strong it will shear the metal. The stress raisers where bite marks occur focus the force into the blade, in compression it is not much of an issue However in tension, when your blade strikes a target further up a blade than the bite mark, it can lead to strain on the blade that causes the blade to shear. so if you have a bite in the blade 1/2 way the force is transfered into the blade focused on the bite, rather than spread evenly over the spine of the blade with an undamaged blade. The purpose of the fuller is to spread that core mass to where it would be better used and this is also why fullers are applied on the lower parts of the blade but wash out to nothing on the upper quadrants of a blade where you wound not be expecting blade on blade contact In this way A sword with a fuller is "stronger" than a blade of equal mass with no fuller. It weakens the sword if inspected in only a pristine condition, but its purpose is to increase the durability of a blade by substantially increasing its strength in a worn condition, allowing it to last longer in battle.

[@marcosferreras7772]

​🎨​🎼​👏​🏆​ aplausos

[@kagetsu13]

So the fuller makes the blade more dense by shifting focus to the edges. Sounds like differential edges like in katanas but on the flats of the sword instead without having to be layered and folded right?

[@Matthew_Jensen]

Thanks for the shout out Shad!

[@shadiversity]

+Matthew Jensen (Funny Sword Reviews) My pleasure mate, good luck with your channel.

[@kharijordan6426]

do they use fullers to blind ppl?

[@Duke_of_Lorraine]

As a student in engineering I can answer your question about resisting a bend with distance : putting the matter further away from the center indeed makes it stiffer. If you try to bend a rectangle, the quadratic momentum (= resitance to bend) is proportional to the width of the rectangle, and also proportional to the height power 3. Here's a pic to better explain than I can write : image.noelshack.com/fichiers/2015/52/1450882016-quadratic-momentum.png This is exactly why an hollow tube is stiffer than a full cylinder of the same mass per section.

[@shadiversity]

+scarfacemperor Thanks heaps mate, I'm no good when it comes to the math :P

[@mrkiky]

+I am Shad I think it's all about the quantity of the material used. How much material you use determines the weight. Having a wider blade with a fuller is better than a narrower blade with no fuller. Thank you for point out that removing material from a structure doesn't make it stronger... I honestly have no idea how people even came to that conclusion, but I've seen it time and time again in many videos.

[@Nozomu564]

An engineer to the rescue! Since I'm not knowledgeable about tensile strength and making fullers I'll make the following assumptions: the formula can be just thrown into calculus and the fuller is made out of isosceles triangles (it's easier) and only changes the shape of the flat part. I'm also assuming +I am Shad knows basic math. I'm going to ignore the /12 part, since it's not like we care about units or precise value. Adding a triangle adds: w * ( (h+c)^4 - h^4 ) / 2c - w * h^3 A fuller changes tensile strength by: w * ( (h+c)^4 - h^4 ) / c - m * ( (h-f)^4 - h^4 ) / 2f - (2w+m) * h^3 If you want to compare it to strength of sword without one multiply it by 100 and divide by (2w+m + s/4) * h^3 and you will get %. The variables for substitution are: c,f: height of triangle h: half of sword's diameter w,m: base of triangle s: width of edge part - the triangle before flat The funny thing is, if the formulas are correct, it disproves your point about fullers weakening sword. With c=.2 , w=.4 , f=.5 , m=1 , h=2 , s=1 it adds 15% strength and lowers mass by 26%. Of course it's just rough test. Maybe sometime later I will find some real data and feed it into equation.

[@Nozomu564]

+I am Shad looks like not only you have such a mean gremlin. Mine will not leave me alone if I won't share explanation for my results. The truth is fullers do make sword stronger. They also do make it weaker. It depends on what you compare it to. If you compare sword with fuller with the same sword with the fuller filled - yes, it is weaker but weights less. If you compare a sword without one with sword bigger of a fuller (ridges with same steepness as the edge) it is stronger but weights more. Great, it's all about perspective and everyone is right. Well, no. There's a third way to look at it. If you displace metal on a sword to create a fuller it will still weigh the same, but it will be stronger. The gain is so big if you somehow remove part of metal it will be both - stronger (but less) and lighter. It will also be wider. Also you don't take a random sword and give it a fuller. Fullering a sword is part of making it. Anyway that's pretty fullish topic.

[@mrkiky]

Nazor Well considering that making a fuller requires you to remove material, it's safe to say that it's weaker. At best you would be hammering in the fuller, widening the whole blade while the material quantity stays the same, in which case it's not as straight forward. But in no case a blacksmith would actually add material, so that case just goes right out the window. Of course we're talking about an unfinished blade here. But what really matters is the final product. You have a blade of a certain thickness and width that is lighter by a certain amount and weaker by a smaller amount(than a blade of the same thickness and width with no fuller), so I imagine it's a tradeoff that is worthwhile.

[@sydneycbr6466]

Actually I think this is a misunderstanding on your behalf. If you design a sword blade with a fuller it can have some sections that are wider than a fuller-less sword of the same weight, therefore making it more resistant to bending than the sword without. It is similar to an I-beam in this regard where it gives you most of the strength of a square cross section with much less weight.

[@_DarkEmperor]

Exactly.

[@RevRaptor898]

Ok yes technically adding a fuller does make it weaker but I think looking at it that way is arse backwards. A fuller allows for a blade to be stiffer than a blade of the same weight with no fuller. It's not about making a heavy blade lighter it's about making a light blade stronger. It's a way to maximize strength without adding weight. Think of it like corrugated iron, the curves allow it to resist bending. A flat sheet has no ability to resist bending so the curves make it stronger. you could also make it stronger by making it thicker but that would be a stupid thing to do as it would be too heavy to use. The fuller in a blade is the exact same principle.

[@andrewholdaway813]

Rev Raptor Absolutely.

[@cdgonepotatoes4219]

Uh.. now I'm wondering how much a sword would bend if the grooves weren't actually centered and went in a way so the sword did an S shape, would that actually make it stiffer?

[@Broadpaw_Fox]

I know this comment is old, but I wanted to address a point that bugs me. When you talk about corrugated sheet being stronger, you're correct - but bending flat sheet is vastly different from talking about a sword with varying thickness. The thickness of the blade will provide much more strength than the flat sheet, and the shape of the blade in the center is of much less importance than the missing material of the fuller. The shape is only important when the thickness is constant - but as thickness increases so does the strength. So as Shad pointed out, a fuller will only decrease the strength as it's removing material from a critical dimension that gives the strength in the first place. It's a trade off - and how much strength is lost depends on the fuller in question and the blade shape/geometry. It's not catastrophic, just a trade between desired characteristics. :)

[@danieliorga2000]

Exactly, so it add to resistence. I,m not agreing with Shad.

[@tarjei99]

The fuller allows the sword to be thicker while keeping weight down. In other words, it makes the sword stronger than it would have been without the fuller.

[@shadowthegreat4304]

This exactly, it brings more of the meat of the blade to the edge making it less fragile (which I imagine was especially good for the iron and steel the Vikings used) while also keeping a large blade width so that there was a lot of power behind the blow.

[@ampeyro]

The small physicist inside me is saying that swords should be hollow, then my inner engineer screams: And how the fuck are you gonna do that?

[@janetlapham3919]

attach interlocking segments, with hollow centre (with beams for support). fill the sword, from the tip, with a material that will remain rigid long enough to heat and forge together the segments, and then either melt, or preferably evaporate. do that. forge the solid tip onto the sword.

[@razorbackxr]

ampeyro so then, if it were possible to make, Sulu's sword from the Star Trek reboot would be one of the strongest blades ever made?

[@TheNthMouse]

ampeyro - proceed with normal inlay technique, but replace the normal insert with a material that will mostly melt out in the final heat cycle before the quench - essentially fullering the spine instead of the sides.

[@MegaMackproductions]

Got a whole engineering firm in there, eh?

[@Spectacular_Insanity]

I love your explanation of compression and tension. With the visual aids, it literally explains perfectly (without you needing to actually mention it) why I-beams are made.

[@petrhala9830]

Yes, fuller makes sword weaker against a sword with otherwise same crosssection. However, comparing swords of the same weight, the sword with fuller will be stiffer.

[@MrMonkeybat]

There are two ways to put a fuller in a blade, one it with a grinding wheel taking away iron to make it lighter, the other is to hammer it in at the forge making the same amount of iron into a wider blade.As the thickness is the main factor in how stiff a blade is, I have often thought that the diamond cross section with slightly concave surfaces was the ideal cross section for a sword. For the same amount of bevel or iron in a diamond cross section sword makes the mid rib thicker than the dual ribs of a fullered blade.

[@burt2800]

+MrMonkeybat That's right but you must keep in mind that the thicker the sword, the more resistance it will encounter when cutting. However, Oakeshott type XVIIIs (the type of sword you described) were very popular which leads to believe they were pretty good. Although I've never handled one I could imagine that the added resistance might have the advantage that it would also knock the opponent around more. You could say it might have more stopping power in modern terms, a bit like a hollowpoint bullet.

[@MrMonkeybat]

As the edge bevel on a diamond cross section goes all the way from the edge to the center it can also have a more acute bevel all else being equal (weigh, thickness, width)

[@saucep5940]

There seems to be a fundamental lack of understanding in the actual smithing technique of the sword-smith here. There *should* be no removal of stock in creating a fullered blade (cheap repros are milled). The fuller channel is hammered into the blade from both sides using a simple scissored die set (swage). When you understand this fact then the reasoning in this video appears nonsensical. There is far more going on here than simple engineering, the crystalline structure of the metal is being modified and repositioned by hammer blows which create tensions and stresses within the material it's self. Technically fullering may not significantly strengthen the blade conventionally the way you're looking at it (Loaded weight on that axis for example) but it most definitely does within the scope of the blade's intended use (You want a tough flexible blade along that axis). Fullering also helps negate twisting through use and during the tempering process, simply by the manner in which it is created the metal has been trained (for want of a better word) to 'remember' it's form. This is archived by the repositioning of the internal structures through repeated hammering and heating cycles. I have to say, for someone claiming to be bringing the truth this video falls drastically short of the mark. Fullering does NOT remove weight (if you remove material you're doing it wrong). Fullering does NOT weaken the overall structure of the blade (It uses rather more advanced techniques than this video describes to produce a superior blade). No one makes swords out of non carbon steel (or blends) and the fuller is NOT just for looks. Please do some credible research before releasing these type of videos onto an unsuspecting public. Pretty much all of your main points here are categorically wrong. I don't want to come off as mean spirited here but I'm afraid this is my reaction to statements heralded as true but not backed up at all by pertinent research. If you would like to know more about the process I can recommend some suitable resources, there are even many videos available of YT that can further explain the fullering process.

[@PJDAltamirus0425]

+Sauce :P Good point, work hardening is also a factor to consider here

[@diamondflaw]

I agree with the majority of what you are saying, however I feel there is one point which seems to be missed. Removing weight does just mean removing material during manufacture, it also can mean removing required weight at design. Fullers DO remove weight from a design, even if they do NOT remove material during manufacture because a blade of the same profile as viewed normal to the flat can be forged from less stock material using a fuller and still have the same rigidity.

[@saucep5940]

I'm not sure what you mean here exactly. When making a sword blade (European) the original stock used just determines the blade size. The billet will be drawn out to length, thinner than required and the setting of the fuller will bring the blade to its final width.

[@bsmith3190]

What I think Diamondflaw means is the fullering pushes material to the edges, so you can start with a smaller piece of material. After all if I just take a normal blade and put a fuller in it the blade is going to be wider then I started with because that steel has to go somewhere, so in order to get the same size sword I have to start with less steel making the whole thing lighter.

[@Side85Winder]

I couldn't agree more with what you have said here. I think the way the information is looked at in the video is the wrong way around. The fuller is more about creating the lightest blade possible while retaining strength in stiffness. If we think of it the other way around rather than removing material say the blade was the same thickness all the way through it would be extremely flexible or it would have to be much thicker as he shown in the video but then its way to heavy. So we want a thin blade because moving faster is better the only way to retain the stiffness with out making it heavy is to add material to a thin blade or remove if its to thick (forging the blade into shape is best). The creation of a fuller adds the most stiffness with the least amount of mass while still being thin to cut through targets. It creates a stiffer spine section along the flat the only other way i could think of would be to make a blade a + shape but then it doesn't cut through targets it would simply hit the flat and stop. Maybe a --o-- shape would work to some extent but the fuller shape is most efficient at creating the least amount of thickness with blade stiffness.

[@NoahWeisbrod]

When people say "stronger," they mean "stronger than a sword with the same mass and a lenticular cross section."

[@PrimordialNightmare]

+Noah Weisbrod I don't believe everyone saying stronger means exactly that. Bewcause there are people not knowing the underlying physical concepts. And It is usually phrased "it's stronger" so people might mistake it, because they are missing knowledge, that is assumed they have.

[@LamiaDomina]

+Noah Weisbrod While that would be the *correct* answer, the world is full of kids who don't actually get the concept and parrot terms they don't understand.

[@Usammityduzntafraidofanythin]

+Noah Weisbrod You mean 'stronger along the edge', right?

[@reishin6]

+Noah Weisbrod I'm not sure how a fuller would make the blade stronger compared to a blade with a lenticular cross section of the same mass. The one with the fuller would be wider (if they're made of the same steel with the same density) but the lenticular section would still have a bit more moment of inertia.

[@NoahWeisbrod]

Reishin Lenticular swords are a little more wobbly.

[@JaneFancher]

Enjoying your vids. Thank you. Someone might have brought this up elsewhere, but as I understand it, one of the big advantages is that the fuller makes a blade (especially one of lower carbon content steel ) more resilient, not necessarily stronger. When the blade is hardened, only the thin edges actually get hard, leaving the bulk of the spine as softer steel. Once bent, softer steel stays bent, while the hardened edge tries to restore itself. If you reduce the soft steel to hardened steel ratio, the blade will have a greater tendency to return to true. Add to that the fact that the reduced weight can allow the same muscles to control the blade better and with less fatigue, and the fullered blade wielder is going to last longer in an otherwise "even" match, and the heavier blade is going to run a lot more risk of taking a nosedive and GETTING bent! :D

[@DaUsher]

I love the tie-in with edge alignment issue. Gives your videos an all encompassing attitude to teaching.

[@shadiversity]

+DaUsher Thanks mate, yeah everything is so interconnected I figure I might as well point people to those related topics.

[@jhwh9876]

Bloods groves are made to catch the blood on a blade, fusing with the iron in the blood making the sword stronger giving you a higher attack power and strength. Dont listen to this pleb, he probably got his information in some "History Book" or "Hisrorical Documents" which you know you cant trust. My favorite historical weapon is the Ninjato.

[@deeem2166]

7:32, the change from the flat geometry to the curved geometry is actually increasing the surface area as depicted, the curves of the surface are longer than the straight line distance between the points depicted, therefor the area is greater.

[@AntExe-ey5my]

The best example of a spring required to resist tension on one side and compression on the other, especially for a channel concerning medieval weapons, is the bow. And you are absolutely right about the distance from center having a greater effect on the resistance to bend. Make a bow twice as wide and it's draw weight will double. Make it twice as deep and it may increase by between 4 and 8 times depending on the shape of the cross section.

[@jonathanswavely7259]

12:54 I was really worried for a moment that he was about to say "I am Shadman"

[@yomauser]

This let me think about the Skallagrim review of an Anti-armour sword: The Duellist, that show a rigid cross diamond blade without fuller. I believe that 'adding a fuller on that blade will make it more flexible and cutting-like, but not ideal for armour piercing.

[@Aleph-Noll]

armour piercing has to be stiff and not flexible. or else itll bend upon the impact. same reason the ax and most pole weapons are harder than the average sword

[@RaptureOnCloudNo.9]

1. I want a light sword that has a stiff edge, so I can cut through more things! *Adds a fuller to the blade design* 2. But.. it is weak along it's flats if I add a fuller! *Use spring steel.. or maybe tamahagane?* 3. But.. it vibrates 8:37 if I use spring steel.. or tamahagane! *adds a curvature to the blade for edge alignment* Aren't we talking about the japanese katana here?

[@cubiusblockus3973]

Another thing those grooves do is when the sword is impaled on an opponant, the groove creates a pocket in which air can enter the woound as they draw it out of a person. this lessens the chance of the blade getting stuck due to sucktion, it just makes it slightly easier to withdraw the blade.

[@44SCB]

From my understanding of fullers, you don't actually remove any metal from the blade, you hammer a groove into the blade thus dispersing the metal closer to the edges giving them more support and increasing the widths of the blade without making it any heavier. So while fullers don't actually lighten the blade because they don't remove material, they do save on weight or prevent you from adding unnecessary weight.

[@joshgaylord1637]

As a hobby I build bows. Draw weight is manipulated by adjusting the width of the limbs or the thickness. If you cut the width in half the draw weight is halved. If you shave down the thickness to half the draw weight is roughly 1/8. I can't do all the math but that is something to chew on

[@maltebusterrisgaardbrnder7589]

I am no mathematician or engineer, nor have I any experience in fighting with swords, but I know there is such a thing as the "Theorema Egregium", which says that curvature in the in the x direction times the curvature in the y direction of a surface must always be constant. This is why bending a flat piece of paper(zero curvature*zero curvature=0) in one direction makes it unbendable in the other direction. From what I understand this would mean that adding a curvature in the x direction of the blade by creating a fuller would make the blade unbendable in the y direction. Numberphile made a video explaining the theorem much better than I can in this comment, but I think it would play some role here.

[@grantpickens2704]

Illia from that works gives a counter argument, stating that at the period of time when you see fullers coming in to common use they didn't have as deep hardening steels and the "fullered" out area was typically removing non hardened material that was prone to taking a set, and so the fuller increased the ratio of hardened to non hardened material, therefore it may be more flexible but it wouldn't take the set

[@CommandoLAX]

A point about bending swords, a fuller, or any complex geometry introduced to a system, will reduce the likelihood to TAKE a bend. This means that the slight upward curve you see in a fuller means the steel can apply an internal force against the moment/force couple (torque).

[@ckl9390]

Also, we see in bronze and early iron/mild steel swords the opposite of a fuller where there is a medial ridge or a relatively deep lenticular cross section to increase stiffness. Where the metal doesn't have both the flexibility springiness to hold itself stiff and readily return to shape during use.

[@pettersonystrawman9291]

Well, in theory fuller does make sword weaker in any direction of stress, but for blade-to-blade direction it removes area that makes the least work in resistence. So, weakening in that direction might be actually negligible. And yeah, i think that resistance is depending on surface times square of distance, so surface is just a surface, but with increasing distance is increasing dependency of more distance.

[@Cragified]

To me the confusion is about a one large fuller or a double fuller. A double fuller will be stronger then a single because it retains thickness at the spine while still reducing mass. Basically you have one I-Beam on the edge plane and a small one perpendicular at the center. As far as the narrow single fuller, perhaps just for looks or just how the forging was done of them. It would make a brake point across the blade for the blows of hammering to harden the edge but not transfer completely across the spine.

[@KageRyuu6]

The fuller does not reduce width, it moves it closer to the edges, after all the edges of the fuller are still as thick as the center used to be. Same goes for an I beam.

[@Krebzonide]

I would assume putting a curve in the blade would make it stronger. If you think of picking up a piece of paper it will bend unless you hold it in a curved shape. Maybe this was similar to their thinking. If you look at some that you showed in this video, the fuller is split into multiple sections, which would make more curves while not losing as much of that width you were talking about.

[@3gunslingers]

+I am Shad You maybe approaching the fuller problem from the wrong side. At 9:20 you are really close to a good answer in a technical way. You should think of a very thin blade and then add triangles in the cross section to add width but as less as possible weight. So in therms of construction you don't remove material to form a fuller, but you are adding material between the center and the edge, which results in a from of "depression" in the middle of the blade.

[@PhilBagels]

Thanks to you, I now have a fuller understanding of swords. I would also think that a fuller has one additional advantage: using less steel per sword means you can make more swords with the same amount of steel. After all, steel doesn't grow on trees.

[@RaggaDruida]

Mechanical engineering student here, yes, the distance from the centre has a bigger effect than area...

[@andrewholdaway813]

Just like to say; it's the forging tool that is called a fuller, the groove is a fullered groove. Unless of course it's ground, then it's just a groove. Fullering a groove into a blade improves it's strength to weight ratio.

[@jhwh9876]

Go on

[@andrewholdaway813]

Justin Everett Shields Think I've said enough.

[@Lachrandir]

It's called a fuller after the tool that makes them. Top and bottom fullers have many more uses than simply bladesmithing. In general they are simply used to widen a piece of stock along the axis of the fuller tool as opposed to widening it in every direction. Indeed, it could be said that the blades that first contained fullers made by fuller tools were simply referred to as fullered blades, and the name stuck and the grooves became known as fullers.

[@amateurcomedyjour6685]

if the fuller is actually forged in the sword it will create compound and tensile stress on the inside/outside of the fuller edges with virtually no stress in between. the idea is that this will create a more flexible spine. if the fuller is simply ground out then it's purely asthetic and you won't get the desired physical advantage

[@lukerope1906]

This is why later thrusting swords did away with fullers, in order to prevent flexing along the flat of the blade.

[@josephburton2656]

Haha, its called a fuller because of the blacksmithing tool used to make it, called a fuller. Anyway, nice video, but as a blacksmith who works at a museum, you missed what I would say is the one of the most important reasons fullers are in historical blades, it saves steel. Quality steel, especially to vikings, was quite expensive so that explains the huge fullers on most sverds. I quite enjoy these videos that shed light on common misconceptions about swords, keep making them!

[@shadiversity]

+Joseph Burton Will do! thanks for adding this fact, as indeed I did miss it and it's a great one, so great in fact I think I'll add a note in the video mentioning it

[@georgantonischki1188]

I agree with your ideas. Especially the final conclusion, the groove increasing the estetic appeal of the sword. I like to offer another perspective you didn't touch. And this is dynamics. A vibrating sword will add strain to your hands. In a fight the most action will be sword banging against sword. You not only need to be fast but also keep your strength under attack. A groove will change the vibration behavior. The energy transfer to the sword from the blow of the other guys sword might be significantly different and (I need to guess here) better if repeated over and over again. My mechanics experience is way to small to be a really good person to say something. In the second video you also mention the production process. Early spring steel might have been quite tricky to get evenly hardened. The groove will to some extend assist here as well

[@G1NZOU]

I like to think of (properly designed) fullers as removing just enough material to lighten the blade while not significantly reducing the strength, or if it does reduce the strength, it does it by an acceptable amount. Everything is a compromise after all, swordmakers striving to get the perfect balance of weight, flexibility and rigidity, while also having a good thrusting point and cutting angle.

[@BandanaDrummer95]

You seem to think that less rigidity automatically means less strength. Even harder steels would still have a bit of flex, and a fuller would allow a sword to take advantage of that flex in the plane that it is important to remain straight. A fuller would mean that a greater impulse could be absorbed by the flat before inelastic deformation occurred, which would mean that for its purpose it is stronger. Also, they give the sword a different thermodynamic profile, allowing for a different hardness profile after heat-treating, which is why it is more common to see katana without fullers (since the thermodynamic profile is controlled with clay).

[@revdocholliday]

Love your videos but the fuller's need is not a matter of engineering. It is a matter of metallurgy. Here's why: A) Spring steel does NOT have more spring. Spring steel is a broad term for high-carbon steels and alloys. B) Hardening and Tempering is what gives metal and/or a blade its spring. To harden steel, a bladesmith must get the metal to a crucial temperature of ~1550F/850C. This actually separates the crystalline structure of the metal and removes ferocity. When quenched in oil the structure tightens down on the carbon creating martensite. At this point, the sword can break like glass. If this is done without a consistent heat throughout the blade, there will actually be pockets where the blade is softer than the hardened steel. The next step in the process is called Tempering. Tempering is actually done to remove some of the hardness. If you were to edge the blade and take it to battle now, it would shatter like Narsil. Tempering is essentially a baking method that loosens some of the crystalline structure of the martensite and allows the metal to obtain some flex and vibration. C) How does the fuller make it stronger? By being weaker metal. Sounds crazy, I know. Remember the part where I said the temperature must be consistent? Well, the fuller is put into the blade BEFORE it is hardened and tempered. This means that the fuller reaches a higher temperature than the edge of the blade and does NOT get as hard as the edge. What is this purpose? So the blade doesn't snap when bent being as martensite, even tempered martensite, is brittle. Also here's another fun fact for you: The fuller removing weight is as big a load of bull as it being a blood groove. The difference both with and without a fuller is negligible. You're talking grams and ounces which are small potatoes on a ten-pound sword. Fullers would be used to improve balance. This is where everyone gets the idea of it "removing weight" wrong. The smith would widen or deepen the fuller to remove grams and ounces to improve the sword's balance. Not make it lighter. I am a novice bladesmith/blacksmith and I work in Industrial Heat Treating. The fuller isn't a matter of engineering but it is a matter of metallurgy. Instead of decrying the fuller, maybe you should marvel in the fact that ancient blacksmiths figured out how to manipulate metal on a microscopic scale far before the discovery of the molecule.

[@Deedeedee137]

OK, so I'd like to point out that fullers do strengthen swords, if the fuller is forged and not ground. Or rather, for the same weight, a sword with a fuller is stronger than a sword without a fuller. This is because of the I beam principles that you mentioned earlier. If the sword has a forged fuller, the average thickness shouldn't change much because the metal will move to the side and become thicker on the sides of the fuller. In addition, the fuller adds surface area to the flat of the sword than the non-fuller shape, since the circumference of a circle is greater than the diameter

[@himanshuwilhelm5534]

I suspect that the idea that a fuller doesn't weaken (or even strengthens) a blade is caused by measuring tapes. If you pull out a measuring tape, you will find that it is stiffer when you are trying to bend it towards the convex side than the concave side.

[@JoaoPauloYUTB]

I think the fuller actually makes the sword more resistent to bending along the flat because instead of removing matterial as Shad is interpreting the situation, in my opinion what is actually acomplished with the fuller is a displacement of metal from the concavity to the ridges which makes a sword of the same wheight thicker, hence stiffer.

[@JoaoPauloYUTB]

+JoaoPauloYUTB Had only watched nine minutes at the time of this coment, he kind of the adressed the issue later in the video

[@hunterdeers1]

Thanks for your short explanation about this small information

[@Agent-Strawman]

When you showed the "I" beam overlayed in the sword cross-section, it was actually an "H" beam. Therefore, your arguments are invalid and flint tomahawks are the greatest egded weapons ever made.

[@brianbell2450]

A question on the function of the fuller. While not a blood grove, could it not be an air groove? What would an air groove benefit a sword? In removing it from the target. I.e. a flat blade would have more suction and be harder to remove. With a fuller, it might provide a channel to allow air to replace metal when removing it from the victim (or other things that it may accidentally be embedded into on a miss). I certainly can be way off on this, but it is another idea.

[@Uncephalized]

The point is not that putting a fuller into a sword makes it stronger, it's that with a given amount of material (weight) you can make a stronger sword by fullering the center and moving that mass to the edges. This forms the shape of an I-beam which is used all over the place in structural engineering because it has one of the highest strength to mass ratios of any shape, especially in the vertical direction which--surprise--corresponds to the cutting plane of the sword, where most strength is needed. A solid sword with the same total dimensions would be a *bit* stronger and a *lot* heavier, because you're putting the mass where it's least effective.

[@blakewinter1657]

So here is an engineering-type question: let's compare the horizontal strength of two swords, with the same cross-sectional area (so they use the same total material). One sword, we will make without a fuller, and one with a fuller. The one without a fuller has a full I-beam structure in the centre of the sword, but the one with the fuller will have two ridges that go a little further from centre. So, which will end up being stronger in resisting horizontal flex? Or will they be the same? EDIT: Okay, I wrote this in the middle of the video, and this issue is raised around the 10 minute mark! I am a mathematician and I do have a background in physics, but when it comes to compression and tension, I am concerned there are some subtleties that make it more complicated that one might expect.

[@Logovanni]

Doesn’t adding the fuller increase the surface area? If you stretched the fullered sword flat it would be wider than one with no fuller. That makes the surface area greater.

[@luckybassturd7260]

yes~ in my jel test, it increases surface area & makes 'fuller groove' harder to pull out, in JEL test! Side Note~ any container that i stab with a fuller groove drains faster than without a fuller groove?! These guys are to smart to test it & come across like they know it all, how dare we question it!

[@DrewLSsix]

This is true IF you assume you are simply removing material from a design. However if you are designing two swords of identical weights and sizes a sword without a fuller will have to be thinner relative to one with a fuller.

[@kleinjahr]

Actually, the fuller gives it greater area. Consider a circle, the diameter is the distance across the center, the circumference is the perimeter of that circle and is longer than the diameter, Pi times D in other words. Think of a fuller as a half circle, the fuller width being the diameter.Then that half circumference is longer than that diameter. Multiply by the length of the fuller and you have the area. So, if area increases strength, there you go.

[@azraelbatosi]

Fullers work like I-beams, they cut weight and allow a sword to be longer and wider without sacrificing strength, in fact, in many cases actually strengthening the structure. I don't know the benefits of multiple fullers however

[@elijahoconnell]

But a fuller would add surface area while reducing mass, if you have something at an angle, the distance between two vortexes is increased. A fuller would be at more of an angle then a sword without one, therefore increasing surface area

[@jasonspade203]

My guess, well Actually from eperiance I figure that the fuller is for reducing the drag or friction of the blade during a cut rather than strengthing the blade. However I do agree that it helps with weight.

[@outlawtorndoa]

Mathew Jenson is fucking hilarious. thanks for introducing me to the channel!

[@Uncephalized]

Ah, I see you used the I-beam as your example! Good deal. To answer your question at 10:00: if you don't change the total amount of material in the cross-section, then moving that material further from center will definitely, as you correctly intuit, increase the strength in that axis. The mathematical property you are talking about is called the Parallel Axis Theorem and it states that the second moment of inertia (the number that represents bending stiffness) is proportional to the area times the *square* of the distance between that area's center and the bending axis. So if you double the distance from center, you quadruple the strength in that axis. Hope that helps! Source: I'm a mechanical engineer. Also Wikipedia to make sure I wasn't totally making something up and pretending it was facts. ;-)

[@sokandueler9578]

I believe there are swords which also have a mid-ridge inside the fuller, thus kind of giving the sword two parallel fullers

[@branokerdene749]

There are many things to consider, width, depth, length of fuller in comparison to the rest of the sword's dimensions.

[@spacepirateivynova]

A solid rod will bend under very little weight, a hollow tube with less material of the same diameter will remain far stiffer. Same idea with fullers in swords.

[@carbon1255]

problem is that ridges really affect the friction when cutting through someone- making them pretty harmful to cutting swords. making them bigger makes them way worse.

[@lazarivanovic4394]

Hi shad i have to dissagree with your opinion and id like to give my opinion. It strengthens the blade due to 2 factors 1st Gauss remarkable theorem (nice video on numberphile) 2nd due to the fact that fullers(when properly done) are not cut outs but in fact more dense peices of steel

[@smashmash2714]

the fuller does add strength in the exact way you have highlighted the i beam shape does and in both planes, its webbing just as in the i beam. yes there is less material available in the plain across the flat edges but with the fuller shape it is adding the i beam structure (in both plains) and the forces are spread to the external edges of the webbing and up the length of the blade rather than evenly across the flat sides of the surface in the one plain, it sounds funny and is hard to explain but i know how metal bends! and if the force is concentrated into one area it will reach its point where it will not spring back, and break or bend, if i had 40 x 5 flat bar and bent it accross the flat it would bend with less force than if i bent 20 x 10 with the exact same amount of material.

[@SarmonOflynn]

Came for the fuller explaination, stayed for the balls.

[@ladymelisandre975]

Merry Christmas! Keep taking those meds Shad.

[@D.Eldon_]

@Shad - Thanks for addressing this subject. When I purchased my first "real" (lethal combat) sword many years ago, I didn't understand about the mechanical aspects of fullers but I chose to avoid them because I didn't care for their appearance. In this one regard, I disagree with you -- I think fullers are ugly. My favorite blade cross-sectional shape _aesthetically_ is the diamond because it has a beautiful centered ridge down the length of the a double-edged blade. And, though I didn't know it when I purchased my first real combat swords, it provides the greatest strength to forces perpendicular to the flat sides of the blade. I'm surprised that you omitted any mention of the diamond blade shape in this video because it's kind of the opposite of a fuller both in appearance and in the way it increases the lateral blade strength. It would have offered a good contrast. And I'm also surprised that you didn't discuss the differences in cross-sectional blade design for different uses: lethal combat vs sport (HEMA) competition vs sparring and training. The distribution of steel between the center vs edge is quite different for a lethal combat sword that must actually thrust, cut and hack vs a sport competition or sparring sword that must have a safe blunt edge, deal with frequent edge contact and flex easily for safe thrusting. My understanding is that a fuller is needed more for the non-lethal sword designs because of their requirement for thicker steel at the edge. Without the fuller, they can get heavy really fast. So, a fuller may be very desirable today since most swords are purchased for non-lethal applications. But, if we talk about historical medieval swords for lethal use, a strong case can be made for a diamond shape over a blade with a fuller -- but this obviously depends upon use as well. My two favorite lethal swords both have the diamond cross-sectional blade shape. One is a light arming sword with a 33-inch (83.8 cm) blade that feels wicked fast in my hand (I believe the diamond shape allowed the blade to be forged a little thinner, enabling its lighter weight while still providing good lateral strength). The other is an extremely strong longsword with a 34-inch (86.4 cm) blade. The longsword is definitely on the heavy side, but this was an intentional trade-off in favor of strength, hacking power and two-handed use. Yet it tapers beautifully to a sharp point, making it a very strong thrusting sword as well. It's the kind of sword with which you could bring down a horse or, dare I say, dragon! :-)

[@sunny5956]

Steel has a crystal structure, like say when look metal trach can, its the best example I got, anyway when you forge steel the structure becomes squashed and make the steal more flexible the fuller does this exact thing

[@-gigeran-1707]

a fuller could perhaps also be used to further balance, weight and add or retract flexibility to the sword to taste of the person using it perhaps if it is custom made.

[@blackdeath4eternity]

adding surface area = more strength.... so adding a fuller = more strength according to you as a fuller adds surface area . (you travel a shorter distance if you cut corners then if you drive around the outside of them.) adding a fuller traditionally dose not remove material it compresses it slightly & spreads it, if you cut a grove it merely removes it. a blade with a fuller will be stronger then a blade of the same weight , length & width without one.

[@Dare_To_Game]

Who knew the Blood Groove strengthens a sword....i guess you can learn something new every day.

[@NobodyDungeons]

Now I can see this being extremely useful when trying to create a usable super large sword with a very wide fuller to reduce weight, and maintain the edge tamper not to mention with the increased mass of the blade it is likely that it will be strong enough to handle the strain even with the fuller so it really just helps in the weight department so if for whatever reason you got a really big person with lots of muscle they could readily use an extra large sword you might be able to take the weight from say 6 kilos to 4 kilos without changing the over all blade profile

[@michayahjwalker3349]

I have haven't finished watching this video but I'm guessing through speculation that a diamond cross section is the best way to go from keeping the sword from bending in on itself or braking

[@joops110]

Maybe the original sword (which bended) was even thinner. They then ADDED the fuller, to increase strength. Much like the I beam. If you look at it that way they added material to the original, instead of removing it. So then the fuller does increase strength.

[@foolwise4703]

Like, @scarfacemperor, I study engineering and I have to say I disagree with you in the important points: If you keep the weight/volume and length constant and add a fuller, the cross section area gets wider and it is less bendable. In your explanation, you keep adding or removing material from the overall sword. But that is not really an option. So out of two blades of same THINKNESS, one with a fuller, the one with the fuller will be weaker to bending. But out of two swords of the same WEIGHT (wich is in my mind much more important), the one with the fuller will be STRONGER. Also, you did not mention that a fuller concentrates the material closer to the edges. And when striking, (imagine you strike another sword or armor) it is the edges that take the massive local stresses. You want the material there, not in the middle, where it does not add any strength.

[@MRDicristofaro]

i thought i was the only one who get attacked by those buggers, and thats the best batman voice iv heard in a while...... the one who owns swords !!!!!!

[@andersengman3896]

A forged fuller pushes the material out, making the sword "fuller", i.e. wider per unit of mass. I think this would be the most plausible etymological explanation.

[@gerbilsmith]

so if a sword with a wid fuller, such as on Viking era sverð, will bend along the flats more easily then that means it flexes to relieve stress more readily than a stiffer blade too. You certainly loose thrusting potential in a more flexing blade, but when striking a hard target such as armor or a shield, then the flex disperses energy into the flexing rather than the blade taking it. perhaps this helped blades not to snap? I don't know metallurgy super well but Dark Age & Viking era pattern welded weapons were made with a more rigid blade as opposed to flexing they might have snapped with more given the context and technology of the time

[@Slammigon]

My dull practice longsword has a fuller too and it makes this "wush" noise when strike the right way (edge faces the direction of the strike). So for practising HEMA or cutting the fuller can help you.

[@gibbeldon]

When I first learned about why there are fullers in swords I was told it is to catch the blood and keep the blade clean.

[@jhwh9876]

Really

[@Roland3ld]

I have seen many of your videos before, so this was mostly a recap for me. A good recap though.

[@markisaacson7677]

A fuller would also make cutting easier. Similar to a cheese knife. It reduces the overall surface area when slicing through material.

[@johnwallace2319]

What if you don’t view it as a grove cut into a blade, but as two shoulders added to each side to increase weight, angle and strength? Thus its not a thick sword with a hole, but a thin sword with some lumps.

[@tedarcher9120]

Distance from center has quadratic effect to rigidity compared to linear if we add more width

[@davidficca8963]

Where was the "well technicality its a fuller but blood groove sounds cooler" clip from?

[@aaronreynolds1504]

I've always hear a fuller is to help prevent a sword from getting stuck in a body.

[@amgironworks9091]

Probably called a fuller due to the tooling that was used to put the groove in. Old world Smith's would probably use a stone wheel to grind it to some extent but it would be rough forged in with a set of top and bottom fuller's. All a fuller is in smithing is a hammer or block of a certain shape that is struck against or the object is struck against to create a depression of said shape.

[@33BiGBoB33]

Shad - no. The fuller is making the sword lighter (because of material absence) but it's not making it weaker or more powerful in any plane you were speaking of (it is making it a bit weaker on certain angles yet i believe it will be neglectable). Because if you add any pressure on the flat you it will concentrate on the THICKEST part of it. That's how grating works.

[@fizikshizik]

+33BiGBoB33 So, you are saying that the grating is as rigid as a solid plate of the same thickness? Does rigidity of the bar not depend on its width perpendicular to the load? What about infinitely narrow bar?)

[@33BiGBoB33]

I forgot to mention my context... sorry. I meant of course blade against blade. If what i said was true in general - a smith would not be able to do anything :P And the grating part is awful too because it's a different story. You want to spread the pressure on as many bars as possible. Sorry for that. At least this discussion enlightened me a bit :)

[@33BiGBoB33]

+fizikshizik Funny thing - scarfaceemperor said the same thing deeper in the comments but supported it with maths ;O

[@Mint-Lynx]

I noticed that a lot of the cross section designs you showed were designs you used in that great sword you made in sketchup.

[@shadiversity]

+Mint Lynx Yep, I try and use proper sword design principles when making my swords, try being the operative word because I'm sure I get some things wrong somewhere ^_^

[@vincenthill1339]

Sure a fuller lowers flatwise bending rigidity, but that doesn't matter because the intended use of the sword is to hit edge on. A fuller reduces weight without reducing strength for a sword's intended use. That's what engineering is all about.

[@OzoneoceanMJM]

You're looking at it the wrong way. Any removal of material makes the metal bar that the sword once was "weaker", no matter where it was from. The final shape of a sword WITH a fuller is strong, has the right balance and weight, while retaining width and good cutting geometry. Instead of thinking in terms of removal of materal to make a fuller, think instead of how weak the sword would be if the whole thing was ground down to the level of the fuller: it would be lighter and have great geometry for a cut but it'd lose a LOT of strength. Adding ribs the the surface would strengthen that shape though: i. e. a fuller.

[@OzoneoceanMJM]

Think of it as an additive thing instead of subtractive, that's what I'm trying to say. You start out with a nice flat ideal cutting blade and then add strengthening ribs to it which gives it more stiffness. That's just a thought illustration to get the point across. Of course sword making is a subtractive process but the end result you're trying to achieve is the same.

[@reddokkfheg9443]

+Ozoneocean MJM i can agree on that in one way. But then its the ridges that makes the sword stronger. Not the fuller. The fuller would in that case be there as a side product of the ridges. and it would not be the thing making the blade stronger/stiffer. it would still be the ridges.

[@OzoneoceanMJM]

Reddokk Fheg Yes, and you "add" them by carving out the fuller. The thing is Shad is saying the fuller only makes a sword weaker and it's just there to make the sword look pretty while making it slightly lighter, which is really not the case.

[@reddokkfheg9443]

Ozoneocean MJM well its a tricky topic. because the fullers do not make it stronger or stiffer in any way. its the ridges that do that. If the fuller is created by grindign away material it do only weaken weaken and lighten the blade. compared to how it was before the fuller was created. If its made during the forging of the blade, Hammering it into the shape, you do not remove any meterial. you just move the material, making the blade thinner in the fuller and thicker at the ridges so to say. then it gets more tricky as you both weaken and strenghten the blade. but still its the crated ridges that makes it stronger. while the fuller makes it weaker. But the point still stands the actual fuller or groove or what you prefere to call it does not itself add any strength to the blade. it only weakens it and maybe lighten the blade. It's the ridges that makes it stiffer not the fuller

[@OzoneoceanMJM]

Well no, not really. As I said initially: everything you do to the bar that the sword was made out of (that involves removing material), makes it "weaker" (and beating the material away from the middle is still removing it from there). So this approach of thinking about the fuller in that way is really quite wrong, you just do not think of it in isolation like that. Putting an edge on the blade ALSO makes it "weaker", beating it into a long shape rather than a stocky rectangular block "weakens" it, and so on. I don't mean to be rude, but you're being technically pedantic here and focussing on the form of my language rather than the spirit of my explanation, which is a little frustrating. The intent of a fuller is to give you a good blade shape with a specific weight, and a stiffer blade than it would otherwise be if it had the same edge geometry and the amount of material, but without the ridges that the process leaves you with. Without the fullers most blades would be lenticular or diamond cross sectioned, which would limit their length and width due to weight and balance issues. If you tried to allow for them to be lighter, longer, and wider by grinding them down or beating them out flat, uniformly and evenly, that would leave you with a floppier blade.

[@tylr3669]

Hypothesis: The fuller allows for the same weight of sword to have a more acute ground edge angle. Because the blade itself is thicker along the plane of cut, the angle of the edge can be steeper. Would this help cutting? This would also provide the same angle for the false edge.

[@batfan1939]

What about a convex fuller, rather than concave? Remove the material _around_ the fuller, and leave the center intact.

[@VeritasEtAequitas]

The premise of this video seems to rely upon the assumption that a fuller is always removal of material, not an addition or redistribution. Couldn't either of the latter could be used to create a fuller that would increase strength/rigidity?

[@MrJizzy181]

Sverd sounds so natural and official. I will now use it. Oh... by the way. Katana doesn't translate into "sword" in japanese. "Ken" means sword. And all traditional japanese swords like Odachi, Tachi, Nodachi, Katana, Kodochi, Yoroidoshi, etc... are called "Schinken". What roughly translates into "Real sword" in Japanese. (Or Ham in German XD ) A Katana is a sword. But it really doesn't translate into "sword". That would be "Ken".

[@jacobmelanson3210]

Well I imagine the people running around trying to kill with the flat of their blade will be severely disappointed then...

[@edi9892]

My problem with fullers allways was that the broader they are the shorter the actual blade gets resulting in a poorer blade geometry.

[@slingcharger69]

The fuller is designed to ensure your blade doesn't get stuck in a body when stabbing.