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Seeking shinken advice

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  • #16
    Originally posted by stealth_monkey View Post
    From the way I read it, they don't recommend it for cutting because it has bo-hi. It's a fairly common recommendation not to use bo-hi on a sword for tameshigiri
    Just saw this (after my post), I agree.

    Comment


    • #17
      Originally posted by stealth_monkey View Post
      From the way I read it, they don't recommend it for cutting because it has bo-hi. It's a fairly common recommendation not to use bo-hi on a sword for tameshigiri
      This idea crops up every now and again, but I don't think I've ever heard a sensei or any of the sword collectors/sellers that I know ever say that you shouldn't use a shinken with a bo-hi for tameshigiri.

      A bo-hi doesn't necessarily decrease the strength of a blade, though it does reduce its weight and changes the balance. Same principle as an I-beam vs. a solid piece of steel. There are many, many fine specimens of tachi and katana with bo-hi. About half the swords on display at the Museum of Modern Art in New York for the "Art of the Samurai" exhibit that opened in October 2009 had bo-hi. Hard to imagine that the nation's finest swordsmiths would use a form that is structurally inferior.

      What I HAVE heard from a sensei is that you should use caution in cleaning a shinken with a bo-hi if that bo-hi runs under the habaki. Perhaps that's a possible origin of this idea of not using a shinken with bo-hi for tameshigiri, since you have to clean the sword well after cutting?

      Can someone correct me if I'm mistaken?

      Comment


      • #18
        Originally posted by Halcyon View Post
        This idea crops up every now and again, but I don't think I've ever heard a sensei or any of the sword collectors/sellers that I know ever say that you shouldn't use a shinken with a bo-hi for tameshigiri.

        A bo-hi doesn't necessarily decrease the strength of a blade, though it does reduce its weight and changes the balance. Same principle as an I-beam vs. a solid piece of steel. There are many, many fine specimens of tachi and katana with bo-hi. About half the swords on display at the Museum of Modern Art in New York for the "Art of the Samurai" exhibit that opened in October 2009 had bo-hi. Hard to imagine that the nation's finest swordsmiths would use a form that is structurally inferior.

        What I HAVE heard from a sensei is that you should use caution in cleaning a shinken with a bo-hi if that bo-hi runs under the habaki. Perhaps that's a possible origin of this idea of not using a shinken with bo-hi for tameshigiri, since you have to clean the sword well after cutting?

        Can someone correct me if I'm mistaken?
        You beat me to it with the I-beam analogy.

        Comment


        • #19
          Originally posted by Eight View Post
          My reasons for wanting to train with a shinken is that I want something with a sharp edge. It's very rare that I do something with my iaito that would cause me to cut myself had it been a shinken (that I notice) but I feel I need to learn to control my sword confidently when a very real risk is there.
          Is the reason given above an honest one about why you want to use a shinken for practice?

          I'm going to play the other side a bit here and say that often those who want to use a shinken rather than wait until they're told to, do so because there's a seemingly prevalent attitude that swordsmanship isn't exactly such if it isn't performed with a live blade.

          I briefly scanned each post in the thread, but forgive me if I missed something -- but has your teacher given you his or her blessing to search for a live blade?

          I've been using a shinsakuto for nearly two years now, and I find myself using my mogito more lately; not for some unconscious fear of cutting myself, but because I give it a bit of downtime every now and then to do a bit of preventative maintenance on my saya and I haven't gotten around to doing that. In the beginning there was a noticeable zeal, a sort of insistence in wanting to use the live blade to the exclusion of my other non-sharpened blades, but quite honestly I see no distinction between the two other than one being overall lighter than the other. Quite literally, a sword is a sword is a sword.

          If I were to recommend a criteria for when a student might be ready for a shinken it would be, are you able to nuki with effective sayabanare and is your noto consistent and quiet? As well, if you're able to perform hayanuki (one and two-handed) without slipping a noto and making excessive noise during it?

          Bearing in mind that I'm not your teacher, and criteria vary across instructors, are you able to answer yes to all the above criteria? If so, you might be a good candidate for a live blade, and one that would likely be able to use a shinken with a very small risk of serious injury.

          Michael Hodge

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          • #20
            Bo-hi will weaken a sword and make it more prone to bending. An I-beam is not as strong as a solid steel beam of the same size. However, its shape makes it stronger by weight. The same is true of a sword blade. A blade with bohi will be stranger than a solid blade of the same weight, but weaker than a solid blade of the same size.

            That being said, I cut a lot with my daily use sword which has bo-hi. Proper technique is much more important to not bending your sword than whether it has hi or not.

            Comment


            • #21
              Originally posted by pgsmith View Post
              A blade with bohi will be stranger than a solid blade of the same weight, but weaker than a solid blade of the same size.
              Yup, agreed. But that doesn't mean a sword with a bohi is necessarily unsuitable for tameshigiri. By your own logic, if a sword with a bohi has the same weight as one without a bohi, then they should be relatively equal in strength (though the blade geometry will be different), right?

              The more important reason why live-edged swords that are not true shinken (true shinken defined as appropriate raw material, manufactured by folding metal repeatedly and tempered correctly) are not suitable for tameshigiri would seem to be that the blades themselves are not as resilient as true shinken (rather than whether or not they have a bohi), whether the issue is catastrophic failure (especially breaking near the mune-machi) or bending.

              Comment


              • #22
                Not to do a major thread drift but has anyone actually calculated out what the S (Section Modulus) is and what the difference is between one with a bohi and one without? Just asking from strictly a structural stand point.

                Comment


                • #23
                  Originally posted by Toecutter View Post
                  Not to do a major thread drift but has anyone actually calculated out what the S (Section Modulus) is and what the difference is between one with a bohi and one without? Just asking from strictly a structural stand point.
                  Couldn't resist... :P here you go.

                  Dimensions are made up, it is only for illustration purpose. You can multiply I by the distance to centroid to get section modulus, which is the bending stiffness of the cross section. As you can see, the bohi has little effect on the stiffness of the blade in the direction of business.

                  Comment


                  • #24
                    Originally posted by Maro View Post
                    What does your Sensei recommend as a supplier?
                    I have discussed this with him. Unfortunately, while he has be practising iai much longer than me, my teacher has not been fortunate enough to have the resources to purchase shinken from a wide range of suppliers to compare and contrast. I have no doubt that he could tell more about the quality of a sword than I could but he would need to see this sword to do so. This is why I came here to ask - there are many people on this forum more experienced than me and some who are more experienced than my teacher - I value input and opinions from these people and since it's not practical for me to test swords from many suppliers, it's useful to speak to others who have swords from these suppliers. Tozando's 'cheap' offerings interested me because I've seen their Japanese-made Iaito and they're of a very high quality, so I was hoping that somebody may have seen their German shinken and be able to offer a review (that's not to say that I'm not grateful for information and opinions from people who have other swords). I believe that it's very useful to gather information from as many sources as possible before making decisions like this - obviously, it is important to assess the quality of this information.

                    Originally posted by Michael Hodge View Post
                    has your teacher given you his or her blessing to search for a live blade?
                    Yes. In addition, my teacher and his teacher both read this forum (albeit irregularly) so I'm not trying to hide anything from them by posting here.

                    Originally posted by Michael Hodge View Post
                    If I were to recommend a criteria for when a student might be ready for a shinken it would be, are you able to nuki with effective sayabanare and is your noto consistent and quiet? *As well, if you're able to perform hayanuki (one and two-handed) without slipping a noto and making excessive noise during it?
                    I don't like to make claims about my own technique but I believe I can do those things, yes (with the caveat that my hayanuki is probably very rusty at the moment and the noto would most likely end up being very oomori-ish - I suspect I would use an iaito for doing that, though - I have no intention of injuring myself on techniques that may not be my best).

                    Comment


                    • #25
                      Originally posted by Eight View Post
                      I have discussed this with him. Unfortunately, while he has be practising iai much longer than me, my teacher has not been fortunate enough to have the resources to purchase shinken from a wide range of suppliers to compare and contrast.
                      The main point I would make is the tsuka length. That is a very strange combination IMHO

                      Comment


                      • #26
                        Originally posted by stealth_monkey View Post
                        From the way I read it, they don't recommend it for cutting because it has bo-hi. It's a fairly common recommendation not to use bo-hi on a sword for tameshigiri
                        I can't speak for the foreign made swords, but here in Japan I see tameshigiri performed regularly with swords having bo-hi. At every chance I've ever had at cutting over the years, I was handed a sword with a bo-hi. In fact just recently my wife's uncle, who used to be very active in Nakamura-ryu, gave me his spare tameshigiri sword as a wedding present. This blade too has a bo-hi and has seen a ton of cutting action and needs to be repolished, but is otherwise no worse for wear. In my experience the quality of the metal is a bigger factor than whether there is a bo-hi or not.

                        Comment


                        • #27
                          Originally posted by Maro View Post
                          The main point I would make is the tsuka length. That is a very strange combination IMHO
                          I'm fairly sure that my iaito isn't an unusual size so I think that we must be measuring things differently. I'll have to get in touch with whatever supplier I end up going with to confirm the way that they measure things since I basically just want a tsuka the same size as the one I have.

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                          • #28
                            I've spoken to Martyn Reeves at Nine Circles regarding this and have been given permission to reproduce his reply here:

                            Quote

                            Our Shinken are made specifically for Iaido practice. They are slimmed down in their profile and they have as much material removed from the groove as possible, to reduce the weight and improve the balance, making them most suitable for long practice sessions and the preferences of most Iaidoka in the modern day market. They are constructed from T-10 high carbon steel and have a genuine Hamon accentuated through hand polishing. I can guarantee you that they are sharp enough to cut most targets, with have cut with these ourselves, however the reason we sell them as not recommend for Tameshigiri, is that with all the material removed to lighten them as much as possible, with a bad cut, especially if the target material were inappropriate (which is too often the case in my experience!) it is all too easy to bend the blade. As we sell our Shinken to a wide range of practitioners, not all of whom have the pedigree and understanding of a Koryu to back them up, we have to advise this to prevent problems with inexperienced practitioners who bend their sword on the first cut and expect them to be indestructible!



                            With our solid bladed swords, they have a much fuller and more traditional profile (to my understanding most grooved swords were historically ceremonial rather than for battle) which you would struggle to bend even with the most skewed Kesa Giri.


                            End Quote

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                            • #29
                              In my experience the quality of the metal is a bigger factor than whether there is a bo-hi or not.
                              I agree. However, I have to say that the quality of the hasuji is by far the biggest factor. If your hasuji is correct, then the lateral strength of the blade does not come into play at all.

                              Comment


                              • #30
                                Originally posted by sirius1906 View Post
                                Couldn't resist... :P here you go.

                                Dimensions are made up, it is only for illustration purpose. You can multiply I by the distance to centroid to get section modulus, which is the bending stiffness of the cross section. As you can see, the bohi has little effect on the stiffness of the blade in the direction of business.
                                Second thought, the statement above assumes you have proper hasuji so the bohi only reduces the blade stiffness (in the direction of cutting) slightly. However, when the blade is bent during tameshigiri due to poor technique, it is bent about the z-axis in my example, with 23% reduction of stiffness. That is a significant reduction.

                                This is consistent with Martyn Reeves' opinion that if you know what you are doing, cutting with bohi is fine. If you don't know what you are doing, a blade with bohi is more likely to bent than a solid blade without bohi.

                                Edit: ...and also consistent with what Paul said.
                                Last edited by sirius1906; 9th March 2012, 12:29 AM.

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