What Makes Swords & Knives Cut Well (Sharpness, Blade Geometry, Etc)
ฝัง
- เผยแพร่เมื่อ 19 ก.พ. 2021
- Such an edgy video, tsk tsk...
This is my best effort to explain what makes some blades cuts better than others, independent of the whole straight vs curved argument (which I've covered here: • A talk about different... ). Of course there are other factors as well, like mass and balance, but this video is focusing on edge geometry and what actually makes a blade sharp.
Many of those who think of the katana as the best sword seem to think that it's all about the sharpness. Same with mono-molecular sci-fi blades (i.e. space magic) that can cut through anything. The problem is that the edge on such a sword would be extremely fragile, basically good only for a single cut.
My videos about cutting mechanics (i.e. technique):
• Different Types of Cut...
• So Many Ways to Cut Wi...
Well written, informative articles that discuss the difference between sharpness and cutting ability, in reference to scientific experiments done on the topic:
knifesteelnerds.com/2018/08/0...
www.hroarr.com/wp-content/upl...
More info about edge geometry:
dcknives.blogspot.com/p/knife...
Kult of Athena, my favorite online store for reproductions of historical arms and armor, fantasy swords, etc (affiliate link):
ww4.aitsafe.com/go.htm?go=kult...
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** Music **
Intro song:
"Illuminate" by Vindsvept
vindsvept.bandcamp.com/track/...
Outro:
"Highland Storm" by The Slanted Room Records
theslantedroom.github.io/stev... - วิทยาศาสตร์และเทคโนโลยี
The pencil was too sharp, I could not see the drawings
Nothing to add but this legit made me chortle.
Skal be like : "I heard you liked edges , so I'm being even more edgy than ever."
Let that bake your noodle
Edgier than Haachama's lore.
These puns
@@George_Bland my noodle is baked 🔥
"Let that bake your noodle" is a sentence I shall now incorporate into my vocabulary!
What will really bake your noodle is that phrase is said by The Oracle in the first Matrix movie.
Another thing you should add is saying "I have a brain noodle hurty" whenever you have a headache.
My noodles have, quite frankly, been thoroughly baked.
If I’m gonna be honest, they may have been a tad too baked. I need some weed too.
My liver has been fried
You poe boi.
I don't have time to actually watch the video just yet. Just popping in to say that is the greatest thumbnail I've seen in a long time. 😆
Same
nightmare fuel
“Let that bake your noodle.”
Joke’s on you, Skal. I’m already thoroughly baked.
You might want to use an ink-pen or a softer B-pencil - the light and reflections make the sketches hard to see at times.
or paradoxically, a blunter pencil
you guys could see the sketches?
A sharpie is clearly called for;)
Charcoal
like, at all times
Skall: *draws on page*
Me, who is watching in 240p: yes i can see very well
That thumbnail, is a FREAKIN MASTERPIECE!!!
Way Better Art than Davinci's Mona Lisa!!!
I lol'd when I saw it.
But which turtle skullis the edgiest.
"Reptiles against the fathers of the Renaissance"?
Should have used a sharpie 😂😂
It’s not the worst thing to be fair but yeah would much prefer a whiteboard
The sound of a marker on paper kills me 😂
Or enhanced the drawing in post, current edit was basically light grey on shiny white, ideally, drawings on screen should approach a 100% black to white ratio out of the full dynamic range of the screen.
Me: "Should I watch the Skallagrim video first this morning, or one of the others in my sub list?"
Skal: *Makes a TMNT2 reference in the thumbnail*
Me: "Cowabunga it is"
"Sharpness is the best thing since sliced bread" hah.
It's surprisingly logical, first they discovered sharpness, amazing!
Then they discovered they can use sharpness to slice bread, better!
But that would imply the sliced bread came before the sharpness...how did they slice the bread? Lolll
@@sephy980 it was done by hand, at first by slaves and then by dedicated craftsmen.
Did you mean butter? Ok sorry about this joke
“Drive home the point”
“Stay sharp.”
🤨
Holy hell your #2 pencil is washed out by your lighting.
The thumbnail that humanity doesn't deserve.
In one book there was monomolecular blade that was supposed to be sharpened by a power hungry force field which is eating away at the blade.
Thus if you blunt your blade enough to lose effectiveness you push a button, and field shave away some of the blade
I feel that most futuristic ultra-sharp swords would realistically go in this direction - instead of settling for a blade that cuts okay and stays sharp, just make incredible blades that dull or break in one or two cuts and find a very efficient way of either re-sharpening or replacing them mid-combat.
What about a solid energy blade edge instead of just matter?
@@WhatIsThatThingDoing Sure, but... the scientific meaning of "solid energy" is very vague. And will probably never be a thing.
Energy itself doesn't actually exist - it's just a theory that we use to describe how matter changes and where the... well, *energy*, comes from during these changes.
With that said, in the far, far future, let's assume that we learn how to out-right prevent all energy transactions on certain matter. With this tech-wizardry, we could then freeze the energy of a metal, essentially preventing it from changing, and use it to create a Solid-Energy Blade. It would not chip and it would not break, and these two abilities together would let you make the blade about as narrow as you'd like.
This is my interpretation of what this term would mean in real-life (psuedo)physics, and it's probably the best blade you could theoretically make while staying arguably true to what we know about the world.
With that said, the elephant in the room is if we will ever be able to screw around with energy itself on such a fundamental level... and I doubt it. And if we ever do... most weapon concepts we know of right now will probably be out of fashion.
@@WhatIsThatThingDoing really depends on the exact mechaincs of the device, for example in the book from which I described the blade the field was to powerhungry to feasibly provide it with enough juice for more than ~a minute of function while keeping it somewhat reasonably sized
I was SURE that once he started talking about the "razor"-thin blade, he was going to segue into this episode's sponsor to peddle razors.
Or dollar shave club.
Or Harry's.
So, my knife is not too dull - I'm just too weak. Got that now, thanks!
"The sharpest edge is this!"
Holds up visably blank page
:woah, the sharpest edge is no edge, he's speaking in koans:
Turns page, drawing faintly appearant
😑
Jokes aside, maybe use power point slides, I get why you went with this approach, but I couldn't see the demonstration 3/4 of the time. Non the less, love your work
It's not bad on a properly balanced screen, but a lot of gamers increase their gamma so they can see things in deep dark dungeons and other dank places, and loose thier upper color gamut. Could also be hard to see on a cellphone for resolution reasons
@@nosajimiki5885 1080p tv, balanced by my lady for watching hockey, but thank you for letting me know it's visible on some screens, i was curious as he seems to check the screen several times
@@Scp716creativecommons TVs are usually set up to maximize contrast more than computer screens because it makes otherwise drab video look more stunning. This usually results in loosing out on both the upper and lower most ranges of your brightness gamut. Since Skallagrim is doing video editing, he probably goes in on a semi-regular basis to reballence his monitors, otherwise his hue balance can shift over time making his videos look fine on his screen, but blue, green, or pink on other people's screens... the issue is that this usually means that content creators work in ideal environments allowing them to see those very upper and lower contrasts that get lost on other devices.
The sharpest edge is the piece of paper itself!
@@omnitroph1501 maybe, the real sharpest edge, is the friends we made along the way!
Best obsession about sharpness I've read is in Terry Pratchett's "Reaper Man".
Also the most kinestetic way of describing a voice ;)
Just realized: This pandemic has now lasted long enough that I have your length hair and I imagine roughly your amount of swords (apparently pandemics awaken the collector in me).
I like the drawn examples, helps get the point across further with an image to look at.
However the drawings are quite hard to see on a phone screen.
Might I suggest a fine liner? Or maybe a whiteboard?
These in-depth discussions are great, one of the more enjoyable vids in my opinion, great work!
Also that thumbnail is brilliant
Yeah i would have the same thing to say. It wasnt very detrimental but it was hard to see. Perhaps thats why numberphile uses brown paper
Big fan of the longer videos ,Skall. Keep em coming!
Looks interesting, but the paper’s too bright and I can’t see anything on it
This is probably one of the best Skal video in recent times, at least in terms of topic, explanation, writing and jokes.
This was very informative!! Thanks for breaking down more of the mechanics of how "sharpness" works on a bunch of different levels
Well done. Best edge explanation video I have seen so far out there.
best part of these videos is your comprehensive understanding of mathematics and and practical physics. its refreshing.
This is better than any of the knife videos on blade geometry. Thanks!!
Even though I could barely see the drawings at times, what I've seen was a great representation :D
1:54am Can't sleep, let Skall teach me the way of the blade
Great video and title. I hate when I hear men tell younger guys or women they wouldn't understand. This is very educational and you know very well what you are talking about. Thanks for this video sent it to alot of friends to show them.
Scandi is the most useful to me.
Big props for the thumbnail dude
P = F/A
Pressure = Force/Area
youre welcome
There's a LOT more to effective cutting than just that.
That explains the initial impact just fine, but the expressions needed to explain a blade moving through the target are significantly more complex.
Thank you for this video!
Usually when I sharpen a sword myself it's sharp enough to cut paper and does well against bamboo... But very often against two liter Coke bottles doesn't do well.
I choose to put a more durable Edge because for years my primary test cutting target has been bamboo in the Bamboo Grove near my house.
Bamboo supposed to be similar to bone and from the pork I have cut on I agree that fresh bamboo is very much like cutting bone that is fresh.
But Coke bottles take a much finer Edge to cut well then bamboo or meat.
My edges that will cut bamboo and meat well also can be whacked on thin frying pans without taking any Edge rolling or chipping.
But again they're no good for cutting on two liter bottles which is a good backyard fun thing to do.
My edges would be able to hit against shield and armor well, but surprisingly not many modern targets
I was considering buy a fat belly blade like your green handle one. Damn! That head cut is way more better than I thought.
I really apreciate than kind of content. Really good video Skall.
Very good video skall, realy bring quality content
Sharpness is the greatest thing since...sliced bread? I actually chortled. well done, sir.
You nailed the thumbnail this time skall
''I had a lot of pun here''
Got the idea but were not able to see very much the drawings , good explanations and examples , keep the good work =)
The next video in my notification list includes a hydraulic press. There you can see sharpening a blade is not needed to make it cut if you have a bit more force behind it. 100 tons are sufficient for most cutting needs.
I really enjoyed this =) You explain it very well with the drawings and those handgestures. I just would have liked some information on the various types of Grinds, given that you kinda went into that, but maybe thats for another video.
Good information. Thanks for the presentation!
I liked this video as soon as I heard the first pun. It was pretty sharp and I could tell you would get to the point.
I found a book called The Razor Edge Book of Sharpening by John Juranitch a helpful expansion on a lot of this discussion. They even did "clinical trials" with different steel. I think it was a poltry processing facility where people are using knives all day every day as a job. Great video thanks!
New point of reference for explaining "sharp" edges on swords. Thanks!
wasn't going to watch the video, but that thumbnail got me. good job!
Good video. I was wondering if you might follow up with something about differential hardening and the impact on edge retention. The type of steel and how it is hardened at the leading edge matters a lot. I found that if you use something like O1 tool steel you can heat the cutting edge with like a map torch to cherry red (whole thing needs some heating) and quench it then file to a pretty formidable edge, then the hardening gradient gives you strength away from the lead edge.
I made a 90cm single edge blade with 8mm thick back edge 40mm blade width and a convex bevel. It was ludicrously sharp but was able to cut wood and leather easily.
I tried this with similar dimension 1095 and it completely went to hell, blade cracked.
Love the videos, understanding blade cross sections are a kind of an obsession for me at the moment.
An unusually comprehensive and scientific discussion.
Good amount of information there, even if you're not actually have anything to do with real swords. As a craftsman (wood and metalworking) i really appreciate all the info.
use a sharpie next time! all i saw was paper!! lol
also there are plenty of hollow ground swords that were used effectively throughout history. Turkish/indo-persian swords in particular, but also lots of european swords (medieval, renaissance And later military swords). Saying a blade would fail because of a hollow grind is historically incorrect. A sword with a literal razor edge probably Would fail as you described however, but thats because of how thin a razor itself is rather than the edge grind
Yes, that's what I meant. Swords with hollow grinds existed, but an actual "razor sharp" hollow grind wouldn't work for them.
@@Skallagrim Lol i wasnt trying to call you out or anything but my pedantry would not be silenced :D as usual good work!
Looking forward to the Single Edge Qama review
Great job! Definitely feel like my edge has been sharpened! :)
On topic of edge roll: In CNC metal working one very important thing is how thick of a shaving the tool produces. The reason for it is that the material itself keeps the cutting edge of the tool from rolling or otherwise deforming. It is weird how you can use a lower-quality cutting tool and completely destroy the edge by trying to go easy on it, yet get great results while pushing it harder. If not enough material is removed, the cutting edge either bends or breaks outward, in the direction that the shaving is coming off at. With deeper cut there is enough material on either side of the edge to prevent this. Not only that, but thicker shavings carry off a LOT of heat that's produced during cutting so the part and the tool stay cooler, which also helps with longevity. This is very similar to why it's so easy to dull a drill bit with a hand drill. Go a bit too quick on the RPM without enough down pressure and the bit will dull in seconds. Put the same bit in a drill press that turns slower and produces about four times the down pressure and the bit will last for a long time.
This doesn't really apply to swords and such, but still is IMO a nifty tid-bit that goes somewhat against what you'd expect.
My absolute favourite representation of this concept are scanning electron microscope images of the tips of clinical grade needles, they are nearly *perfect* when brand new, and after a single injection the tip is visibly squished, the hole it leaves after the injection is barely bigger than the needle itself and, obviously, it pierces with next to no resistance at all
Great explanation skall. I'm a chef and my knife collecting tendencies have transferred to chef knifes. I tend to throw a micro bevel on my pocket knives. But much prefer a flat grind on my chef knives. Just to let you know how far my knife addiction has gone I have a 400$ edc pocket knife and a 900$ chef's knife but she rarely touches food shes too pretty.
Great informative and clear video
so part of my bg is in the world of cnc machining. it was explained to me that the radius of the carbides we used basically concentrated the pressure down to such a small area that the heat generated formed a plasma which is what did the actual cutting. id think that a mega damage entity would be capable of generating such forces on nearly anything with a bit of a taper to it. hell when i got my logsplitter it had a rounded edge but after the first few pieces the pressure had honed that into a near razor edge.
Things like the edge being aligned straight, high coefficient of friction/some amount of micro-jaggedness (being too smooth may cause it to slide and roll the edge in, making it blunter. Cutting involves dragging and tearing...)
having thin enough a contact cross section to raise applied pressure,
being hard enough but not too hard it’s brittle,
being enough resistant to elastic deformation,
having a favorable weight distribution, blade geometry/edge tappering and blade wideness.
Fun fact regarding convex edges--they are actually essentially the same as a V-style edge of equal edge angle, but with the shoulder removed. Contrary to what many think, the intersection of two arcs does have an angle to it, and while it's possible to have a convex edge that's thicker than a V-grind, it's because it's a thicker angle at the apex! However, the shoulder of the convex with an equal edge angle to the V-grind will go further back on the blade. When drawing comparisons very often people make the mistake of holding the shoulder depth as fixed, which makes convex the thickest possible geometry to "connect the dots" but that's not how it works in real life when applying an edge to a tool, and so the real advantage of a convex is that it allows you to thin the geometry behind the edge without sacrificing edge stability at the apex, and so it will be a little more penetrating than a V-grind of equal edge angle.
Im sorry hoss but glare and other factors make seeing pencil on that paper near impossible
best thumbnail evaaaar! :D
Very educational. Thank you!
Skall, or anyone who is able to help, I have a question. Why does a slice cuts but if I press the blade straight against a surface it is less effective?
I don't understand why is this so, if someone could explain I would be very happy!
A sword seller I met at a ren faire tried to use a misinterpretation of this to justify why the entirely blunt sword I was looking at was actually sharpened...lmao
Great video. I like this explanation type video. I suggest using a sharpie pen instead of a pencil. It was a little hard to see your drawing on camera.
the best thumbnail i’ve seen
Can someone tell me what is this sort of curved kindjal / gladius that Skal is holding in his right hand at 20:45 ? Or post a link?
It would be nice to listen about different types of layers of steel that forming the blade's anatomy
This is something I've been pondering myself as I've recently gotten into micro bevels. I've been contemplating the various types of edge and blade grinds and asking myself, " why?".
Great video, thank you Skallagrim.
Ah yes, the riddle of steel. We won't let Thusla Doom trick us with his trap of the flesh, or ability to thrall those within his cult.
Best thumbnail ever!
Very well presented. Is English your first language? I thought it was not, but seems I may be wrong. Regardless, great video!
Is this the episode where we discover his skillfull freehand drawing?
I read somewhere that the only material that produces a radius that is as close to 0 as possible is obsidian, specifically the edges of an obsidian flake. Obsidian is probably the only thing hard enough to sustain that edge, but it really cannot do much, as it's quite brittle because of the hardness.... On the subject of sharpness, when I was an apprentice carpenter the master carpenter spent an afternoon teaching me honing and sharpening skills. I managed to get a chisel sharp enough that it actually managed to get stuck in concrete... But only once, as when I removed it, the tip was pretty much ruined. Like you say, getting things sharp isn't the issue, having a material that's strong enough so it can stay that sharp despite wear and tear is.
Can you do a review of the black legion grim reaper throwing knives? I bought six for 12 usd because they were cheap and they were disappointing even for two bucks a piece. Would love to see an expert’s take
A good way of imagining how something really sharp will break is Obsidian, which is the sharpest thing we know. It can cut hard, but it won't survive the first strike, and that if it is a dagger, any bigger and it breaks under its own weight.
I think I may have actually developed a tick from a combination of straining to see these marks and my finger raising in objection almost once per sentence.
i am a butcher by trade so this video just made me think of all the different knives/blades and how each one is used for very specific tasks
That devil edge single edge qama is a beast of a cutter. Lol. I own one and although she is way overweight and painful to cut with, she does cut nice.
Something I haven't seen mentioned anywhere so far is the concept of self-sharpening blades.
It would be very similar to rat teeth in nature: There are two layers, stacked next to each other in two sheats. One is softer than the other, gets abraded more quickly, and so the edge gets thinner, only the hard layer remains at the top, and can then be worn down in turn.
Thumbs up for the shirt alone!
you should try making a playthrough series of Valheim, not quite on the same topic of your channel but I really like ur view on games u've seen and played so far
How do you display your armory?
Kyber Knife and other T-spine blades have the most interesting edges to me. So thin.
T spined swords are super neat
Aren't Khyber knives named for the strategically important Khyber Pass?
@@johndododoe1411 yes, Matt Easton talked about that a lot on his channel
Haven't watched the video and I liked it. Awesome thumbnail jajajaja
what about a concave primary with a convex secondary?
O.K. Thank you. I'll have to watch it again.
Hey skall I have a sword I got from a fella that used it as a fire poker and im not honestly sure how to sharpen it or get rid of the bends the blade has additionally im not sure how to repair the scabbard as there is rust inside of it
And rust all over the blade but I got rid of most of it
I like that all of the puns and jokes were edge related
Are we cutting, slicing, chopping, or all of the above?
90 degree edges can cut pretty deep. I work with particle board, and have gotten a few stitches from the edges.
Is the monodo from xenoblade chronicles a practical weapon
It would be intetesting to test Conyers Falchion or a quality replica cutting tatami.
Skall, man to man, we want more blade shoppe, public skall and workout videos. I’m speaking for the people trust me.
I just want more dueling videos
Does anyone know how they sharpen the blades at Angel Blades? Supposedly the sharpest swords around
Odd question since I don't know much about medieval weapons and such:
Lets say an "adventurer" in a medieval fantasy setting is able to teleport around during combat at will (a good example of such a character would be Ciri in The Witcher series), which weapons would be able to make the absolute most out of this?
I really like the freehand drawing stuff, but maybe next time you could use a marker or something darker so we can see what you’re talking about easier :)