Stresses on Steel


There are many videos of sword test-cutting (“tameshigiri”) on youtube and I generally avoid them. A lot of the time, it seems to be someone who got their hands on something katana-shaped and has decided to risk their, and their friends’ lives.

A sword blade must be springy and hard in a great balancing-act. And a blade can sometimes fail. So, what happens when someone is chopping through a rolled up mat, hits it at just slightly the wrong angle, and their over-hardened blade cracks? Well, the end goes helicoptering and, because of the cut it just made, it goes helicoptering with the edge forward. There are other problems; the peg that holds the blade into the handle may be loose, or the handle may be loose, and the impact can shear the peg. Then the entire blade may go helicoptering. This has actually happened and has resulted in tragedy – one iaijutsu master’s blade came out of the handle and killed someone in the audience.

Part of what makes this extra grievous, to me, is the manga and movie presentation of katana as these unstoppable cutting instruments; they are not. They’re really dangerous weapons, not as dangerous as a gun but you don’t want to be around someone swinging a 3 foot razor blade any more than you want to be around someone doing “quick draws” with a revolver (another weapons demonstration technique that has a high casualty rate). If you’re around an expert, it’s highly likely that you’ll be safe but consider this: you’re watching a potentially lethal situation. Sometimes I’ve caught myself thinking “what is wrong with people who watch NASCAR races? do they just want to see cars wreck and maybe a driver get killed?” Motorsports are certainly less dangerous, but all of these things have an underlying potential of turning into something unforgettable or traumatizing. Was what was entertaining the potential lethality of what you were watching?

I’m not offering advice here. Do what you do. It’ll probably be fine.

Also, I’m not criticizing this (obviously highly expert) swordsman. He knows what he’s doing – and this particular cut is harder than most because he’s changing the angle of the blade across its path as he draws it, and if the blade is not perfectly aligned with its path, it’s going to put torque on one side of it, which will drive it in different directions. He’s using one hand, which also means there’s less muscle-memory to register the angle of the blade as it hits the mat. Far be it from me to critique a sword-master’s technique; I’m impressed that he’s willing to do this at all. But watch what happens to the blade when it goes through the mat. I can’t even estimate what tiny fraction of angle his blade was off, but you can see that the blade experiences some stresses that we normally would not observe with the naked eye.

Katana are properly lauded for their sharpness, strength, and flexibility. The differential hardening that gives you a martensite edge on a finer-grained, softer steel back – that’s why this blade did not blow apart. Imagine what could have happened if it had been over-hardened, or it had a weld inside that was not completely clean. What if it was a katana-shaped sword that was made without an understanding of why katanas are capable of doing this sort of thing when they are built correctly?

A small mistake with a weapon can earn you a lifetime of regrets that you can never let go of. As much as I enjoy the attention blade-smithing has gotten thanks to shows like Forged in Fire I do not believe “reality TV” is the right way to expose people to what is a very disciplined discipline. It makes me very unhappy to see a bunch of guys standing around in a TV studio while someone who does not handle a katana very well, destructively tests one. There are other aspects of the reality TV format that bother me, such as their fondness for compressing contestants’ time-frames, deliberately jeopardizing their skill by pulling them out of their comfort-zone; well, it’s not a “comfort-zone” it’s “area of expertise.” In order to add drama to a TV show they are making it harder for the blade-smiths to work safely and confidently. It does not thrill me when I hear someone say “I hardly slept during the 3 days you gave me to make this sword.” It’s all fun and games until someone catches on fire or is hurrying and doesn’t clamp down a blade and helicopters off a finger or two. I think I have more respect for the blade-smiths than the show does, but one should not expect otherwise from reality TV.

The source video, which is really cool and quite beautiful, is here [youtube]

Comments

  1. kestrel says

    Wow. Amazing how it flexes like that. Also, kinda scary.

    I would like to think that people watch such things in appreciation of the skill but perhaps you are right and it’s the danger instead. If that’s true it’s a little sad because these people do have such amazing skill and they did not just get up one morning suddenly able to do whatever; it took them a long time of careful practice to get there.

  2. avalus says

    Like a wave of silver.

    It reminds me of slowmo footage of arrows being fired from a bow. They bend and flex.

  3. says

    Part of what makes this extra grievous, to me, is the manga and movie presentation of katana as these unstoppable cutting instruments; they are not.

    Come on, movies always portray everything unrealistically. Impossible martial arts feats that nobody could do in real life? Check. Impossible escapes from various dangerous situations? Check. Dating strategies that would end up with getting sent to jail for stalking and harassment if it happened in real life? Check. Same goes for the portrayal of hackers and hacking. Even the portrayal of mundane everyday conversations is unrealistic. This goes double for anime/manga/cartoons. Animators can draw literally anything, thus they do exactly that. Of course movies will portray katanas unrealistically. How else could they possibly portray them? A movie has to look cool.

    Sometimes I’ve caught myself thinking “what is wrong with people who watch NASCAR races? do they just want to see cars wreck and maybe a driver get killed?” Motorsports are certainly less dangerous, but all of these things have an underlying potential of turning into something unforgettable or traumatizing. Was what was entertaining the potential lethality of what you were watching?

    In my case, I wouldn’t like a front row seat in a situation where spectators can get injured. In general, I’m a rather cautious person, and most of the time I don’t like doing dangerous things.* As for watching from a safe distance, why not. I know I couldn’t get traumatized if somebody else died in front of my eyes. That’s just how my brain works. Thus the question is whether something is interesting enough for me to want to watch it. For example, I perceive NASCAR races as boring. Cool tricks with sharp blades, on the other hand, seem much more interesting for me. I might as well watch that.

    By the way, I don’t perceive as entertaining the potential lethality of what I’m watching. I’d rather prefer people sticking to things that not only look cool and interesting but are also safe.

    It does not thrill me when I hear someone say “I hardly slept during the 3 days you gave me to make this sword.”

    I don’t even own a TV and I haven’t watched any of these reality TV shows you are talking about here, but this one sounds stupid. How does a show benefit from filming a person who is sleep deprived? Tired people just look worse on camera.


    * I don’t care about watching other people do dangerous things. I’m not comfortable doing anything very dangerous myself either. However, I do perceive it as thrilling and exciting when I do something a little dangerous. The most dangerous thing I have ever intentionally done was swimming very far away from the shore in the sea. Swim deeper and deeper for about an hour, then turn around and swim back towards the shore. I got so far away from the shore that nobody could even see me, never mind being able to help if something happened. And the thing is, I perceived it as thrilling, it was more enjoyable than staying close to the shore. So the key for me is a little bit of risk. Not enough to make me scared and uncomfortable, but enough to make the experience exciting.

  4. says

    avalus@#2:
    It reminds me of slowmo footage of arrows being fired from a bow. They bend and flex.

    It is just mind-blowing what an arrow does when the bow blasts it off. It’s like a looney tunes cartoon arrow being fired by Wil E. Coyote or something. How does it hit anything?

  5. says

    Ieva Skrebele@#3:
    I don’t even own a TV and I haven’t watched any of these reality TV shows you are talking about here, but this one sounds stupid. How does a show benefit from filming a person who is sleep deprived? Tired people just look worse on camera.

    You can search for bits of it on youtube. Then again, you could also gargle with cement – and I don’t recommend it.

    My hatred for “reality TV” is deep and abiding and I ought to do a post on it some day, except it hurts me to think about it and there’s not much to say about it, really. Thumbnail sketch will do: the whole reason we have “reality TV” is the script-writer’s strike in the 90s. The studios came up with the brilliant idea of fucking the script-writers and actors’ unions by shoveling content that was ‘spontaneous’ and ‘unscripted’ and used non-union ‘talent.’ The result was a massive dumbing-down of TV from its already low standards, and the elevation of noisy nonentities to the presidency. [Pretty much you can look at anything Americans do that’s stupid and mysterious and the answer “corporate profiteering” will work.]

    I wouldn’t like a front row seat in a situation where spectators can get injured

    Yup. Motor sports, equine displays, shooting competitions, javelin tossing competitions, “hey come watch my new trebuchet.” No thanks! I’ll catch it on youtube or failblog depending on how it works out for you. I also really don’t handle seeing people hurt, so I’m happy to miss The Flaming Audience Trick or whatever.

  6. says

    Marcus @#5

    You can search for bits of it on youtube.

    I don’t know much about American TV shows, but what little I do know indicates that I probably don’t want to find out more.

    Yup. Motor sports, equine displays, shooting competitions, javelin tossing competitions, “hey come watch my new trebuchet.” No thanks! I’ll catch it on youtube or failblog depending on how it works out for you.

    For me (and I’m a control freak), there’s another aspect here. Having somebody else do something dangerous in my presence takes away from me control over the situation and forces me to entrust my safety in somebody else’s hands. That person who is playing with guns or sharp blades right next to me, have they received sufficient training? Do they have enough experience to understand what they are doing? Are they sober? Perhaps they are high on drugs? Or maybe they are tired or sleep deprived? I cannot know, thus I don’t feel comfortable. I don’t always have a problem with trusting other people. When I board an airplane or go to a surgeon, I know that the plane pilot or the doctor has received sufficient training and that there are checks and procedures to ensure that they don’t accidentally kill me. Thus I can feel safe. But it’s a whole different situation with people who do dangerous things for show. Theoretically, anybody could play with sharp blades next to spectators even if they don’t know a thing about the potential risks.

  7. avalus says

    Ieva: #6: “That person who is playing with guns or sharp blades right next to me, have they received sufficient training? Do they have enough experience to understand what they are doing? Are they sober? Perhaps they are high on drugs? Or maybe they are tired or sleep deprived? I cannot know, thus I don’t feel comfortable.”

    This mirrors my gut reaction when the new chemistry students in our teaching lab have their first encounters with really dangerous substances. Or even their first really smelly substances. I can just hope they now understand, that the strictness we tutors expressed in earlier (safe and easy) experiments really matters!

    Marcus #4: Yes, thats the beauty of the physics of standing waves. The center of mass of the oscillating object hardly moves anywhere but forwards.

Leave a Reply