jct3602 Posted July 2, 2015 Report Posted July 2, 2015 Nakahara states on Pg 61 "to define the correct curvature of a tachi, a line should be drawn fron the very butt of the tang to the tip of the sword... Currently, swords are measured by using a line from the end of the back surface of the sword (mune-machi) ro its tip...This kind of measurement is only used for sword licensing." I realize that tip to mune-machi is the standard commonly used, but when comparing measurements of sori to those of tachi in old texts (such as the Showa Dai-Meito Zufu), which measuring standard did they use? Does anyone have an answer that they feel confident in? john twineham Quote
Stephen Posted July 3, 2015 Report Posted July 3, 2015 Good question interested in seeing where this goes Quote
Ken-Hawaii Posted July 3, 2015 Report Posted July 3, 2015 John, I did a little measuring in my own Showa Daimyoto Zufu, & it does look like they measured from the end of the nakago to the tip of the boshi. I'm not 100% certain of that, but from the 2 samples I chose, pretty much at random, I couldn't match the sori measurements any other way. Ken Quote
Brian Posted July 3, 2015 Report Posted July 3, 2015 Just when you think you have at least one thing learned and clearly understood..... Brian Quote
seattle1 Posted July 3, 2015 Report Posted July 3, 2015 Hello: The issue of sori is confused by the licensing requirement of the chord measured between the tip of the kissaki and the munemachi, and that might have been historically introduced because of the ease of that method's use where the tsuka need not be removed. For a discussion of the measurement as a chord between the tip of the kissaki and the butt of the nakago and its implication for the sori of the blade, and hence its cutting efficiency, see Sam C. Saunders, "Shape and Cutting Efficiency: The Unique Nihonto Curvature," JSS/US Newsletter, Vol. 33, No. 7 (December, 2001), pp. 20-30. In that article is the "real secret" as to why the Japanese sword cuts so well in necessarily linked to the less commonly used length measurement referred to in Nakahara. It is not a matter of the metal used, the folding process, the laminations, or the fire tempering. While all those things are highly contributory, it is the equi-angular form of the cutting edge that maintains a constant angle, as drawn through the medium cut, that maximizes cutting efficiency. I have never seen that issue touched on anywhere else in the sword literature. While Sam shows a "legal measurement" diagram, all the others and the associated discussion involve sori measurements from tip to nakago. I had some role in the preliminaries to his writing and publishing the piece and continued to bring up the standard measure we usually refer to as length and associated sori, but he knew better, and should have as he was an Emeritus Professor of pure math. Arnold F. Quote
jct3602 Posted July 3, 2015 Author Report Posted July 3, 2015 As a follow-up on Arnold's post, the following question - I have read that retempering sometimes increases the curvature of a blade. It would seem that although water lines on retempering could be covered up by the filing of the new portion of the tang following suriage, radical changes in curvature could not. Assuming the original smith wanted a smooth curve, if you see an old tachi where the curvature is substantially more extreme than that of the continuation through the nakago, might this indicate retempering at some point? John T. Quote
Jussi Ekholm Posted July 3, 2015 Report Posted July 3, 2015 I'm pretty sure that most of the books will have sori measurement from munemachi to tip. After all this is how sori is measured according to pretty much every book I have. I own couple very nice oshigata books that have fullsized oshigata and they are amazing, I've spent lot of time with them as they have blades that interest me very much. These books list the curvature like this, which is really handy. So by just looking at the numbers you get bit of information how the sugata might look like. 反り - Sori 茎反り - Nakago sori I believe full length from nakago end to kissaki end is 全長 - Zencho. For some very curved old tachi this overall curvature can be very large. I measured few for the fun of it. I took 3 swords for which Imeasured this, as the overall curvature is my own measurement it's only c. as I couldn't get it down to mm accuracy as the book has folds and I am very careful in stretching the pages. 1st sword: nagasa: 80,3 cm, sori: 3,2 cm, nakago sori: 0,7 cm, overall curvature: c. 6,0 cm 2nd sword: nagasa: 84,4 cm, sori: 3,2 cm, nakago sori: 0,6 cm, overall curvature: c. 5,0-5,5 cm 3rd sword: nagasa: 83,7 cm, sori: 3,8 cm, nakago sori: 0,4 cm, overall curvature: c. 6,0 cm First two pictures are of sword n.1 and third pic is of sword n.3. As both of the swords I own are tachi I can give similar stats of them as those above. Kuninobu: nagasa: 67,2 cm, sori: 1,9 cm, nakago sori: 0,4 cm, overall curvature: 3,6 cm Kanemoto: nagasa: 84,6 cm, sori: 2,5 cm, nakago sori: 0,4 cm, overall curvature: 4,5 cm And as curvature is discussed Mariusz has just listed this one: http://www.militaria.co.za/nmb/topic/17117-ubu-kamakura-tachi/ Don't know if this post is helpful in any way but I had a lot of fun writing this and measuring things. 2 Quote
seattle1 Posted July 3, 2015 Report Posted July 3, 2015 Hello: I think John T.'s question is quite subtle and observant. You might be onto a good kantei point, but more generally I would caution not to put too much, certainly not exclusive attention, to the strong sori found on some older koto. Some periods and schools had stronger sori, by either of the versions of sori being discussed, and if suriage mu mei, one would have to be a pretty good kantei-ka to know whether it is a typical characteristic of a given group or not. Retemper or saiba conclusions are based on a whole bundle of observations and sometimes it is just a consensus among contradictory observations that you are left with. Arnold F. Quote
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