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Making a Sue Bizen inspired Katana


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Hello all,

 

I have been studying most aspects of Katana making for about 8 years now, and have been using them as a martial artist long before that. I have just now got the guts to try my hand, and as I attained so much valuable information from this forum I figured it was the least I could do to give a little back by documenting my progress here.

 

First I would like to show a process I've used to analyze swords digitally. I use Google Sketchup to do this. I import images (finding good images is half the battle) after turning on high resolution in sketchup, then scale it to size based off of the nagasa measurement. Then I can trace the edges with curve tools, which allows me to analyze the radius of every part of the blade. Here are a couple of the Sue Bizen katana I studied for this project.

Bizen Katana Study.jpg

 

This coupled with a lot of reading on the shapes and characteristics of katana at the time period I was looking at allowed me to come up with my own plan for a sword that fits this style.

 

The curve of a katana is not defined by a single radius, but several. The most important 2 are the main curve along most the length, and the heightened curve along the first 5ish inches from the machi (often the term fumbari is used here, which is confusing because that can also relate to taper in width overall and not this specific area, correct me if I'm wrong?). From studying many swords I have found that the smaller radius in the first 5ish inches is almost always very close to half the radius of the larger one. Making me think that exactly half is what they went for. The next couple photos will hopefully make sense of what I am talking about.

 

Two circles, one of 100" radius, one of 50" radius

Bizen Katana 1.jpg

 

Zoomed in, 3 sections created. Where the circles meet, 5" before, and 21.5" after.

Bizen Katana 2.jpg

 

A little trimming and here is the final desired spine curvature (the only change later will be the kissaki, which curves slightly up)

Bizen Katana 3.jpg

 

From here I can add my desired blade widths from my 3 major points. The first 5" contains about 1/3rd the overall taper from machi to yokote. I can also use a geometrical shape to consistently lay out my shinogi. The main curve on the ha mimics the radius of the main curve of the mune, and the curve in the fumbari area is a tangent to this and is usually in between the radius of the the large and small circle

Bizen Katana 4.jpg

 

Once I had all this worked out, I needed to create a sunobe that would turn into that shape once the bevels are formed. This is actually fairly simple. The sunobe is straight and curve comes from forging the bevels or quench, so make everything straight and add or subtract curve where you want more or less in the final shape. In this case, I left everything straight in the sunobe except the first 4-5 inches on the mune which will have a slight radius already, accounting for the non-even taper. After a lot of back and forth forging, drawing out more and cutting back down due to lack of experience, here is my rough sunobe made from Aldo's 1075

 

20161201_184106.jpg

Edited by Austin Mys
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Once I was happy with my sunobe, I forged the tip back and started working bevels. I had to pre curve the blade as I decided to quench in parks oil. These pics will catch up to where I'm at now. Also

I've debated on whether to start a new topic for the new sword, but since it is the same project to me, and the discussion is still going, I think I'll just keep it all here for simplicity.   Realiz

Alright, after a lot of various life circumstances keeping me from starting sword # 2 (including my old forge being totally worn out and building a better one) I have finally got the ball rolling agai

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Once I was happy with my sunobe, I forged the tip back and started working bevels. I had to pre curve the blade as I decided to quench in parks oil. These pics will catch up to where I'm at now. Also just realized I misspelled katana in the topic line... how embarrassing

 

Tip forged back

20161201_184507.jpg

 

Bevels started. Managing the kissaki was way harder than expected, thankfully I left everything thick enough to leave room for clean up

20161201_223933.jpg

 

Bevels done:

20161202_184342.jpg

 

And as it sits now, curve adjusted and ready for scraping and filing after I straighten the kissaki a little bit.

20161205_131845.jpg

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not met as criticism but as i understand a katana is always water quenched giving it the sori, this is a beautiful phenomenon that gives the blade the curvature or the typical katana shape we appreciate. This phenomenon is not 100% controlled by the maker. Having said this it means that all "Japanese style" created blade are unique in there way and the final result is a combination of makers curvature and steel bending to its final form resulting in the pictures you have drawn out for us.

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Actually, sori was very carefully placed and is very repeatable with a water quench. This is why swords from the same school and especially smiths share very close measurements in curves and dimensions. The only reason I am quenching in parks is because I don't want to risk breaking this particular sword, but I would not gain anything mystical by quenching in water, only perhaps some hamon detail. Slight variation comes during the water quench as it will even in a oil quench (which creates negative sori), but not large amounts if you control the variables and know what you are doing, and is largely predictable especially with experience. These Sue Bizen katana would not have been forged straight either even water quenched, as they often have sori of around 1" or more. you only get a half inch or so from a straight sword, so these would have started pre curved. Where water quenching does give you a bit more of a wild card is with the hamon, which does not follow the clay. In fact the first katana I have a pic of above was quenched without clay by the remarkable smith Yosozaemon Sukesada in 1537ad. But the final curve and distribution of mass is never left to chance. The amount of funbari near the machi has to be forged in by the smith, this is not a side affect in any way of water quenching that the blade grows in width here, nor is it when blades taper more in the top third of the blade, that is also set with the sunobe (preform)

Edited by Austin Mys
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I have to applaud your very thorough and well researched approach to this Austin. I very much looking forward to seeing this done. I love katanas so much.

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Thank you Wes, I appreciate that! Took a look at your work, very consistantly clean.

 

Caleb, it's a trap! But a fun trap at that, and very challenging.

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As I understand it, curvature was frequently adjusted post-quench, by various means.

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Al, to a degree controlled heating and quenching at sub tempering temps can be used for this I would guess, although I've only heard of these techniques in reference to straightening the blade of warps after heat treat myself (along with bending cold if need be). Minor inconsistencies though can be fixed with the rough shaping with stones by the smith and or polisher. Any references to that statement?

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Great work. I especially appreciate your dedicated study of proportions and clear visualisation of the principles involved.
I shall follow your progress with great interest!

 

To your experience after having compared the curvature of different katanas, would you say that the 5-ish inches at the base could be 1/5 of total blade length? It would make sense if this dimension was also set proportionally rather than with a measure in an arbitrary system.

Have you looked at the ratio between the diameters of the circles that make up the curvature to the length of the blade? It would be interesting to see if you could find trends in different schools expressed as variations to this ratio.

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nice, thoughtful, work. I am a scientist in my day job, so I try to avoid this level of analysis in smithing, but I appreciate it greatly when others do it. You are off to a great start. Now, you have to build a long-term relationship with your materials. Learning how they work from the objective perspective is the first step, and will help greatly with learning the subjective process of how this all feels when you do it.

 

I love the work. Hammering, filing, shaping, drilling, (not so much the grinding, that is a necessary evil). But, the rest of the work is very enjoyable.

 

Final assembly is a little stressful on some pieces (gremlins live in epoxy).

 

thanks for such a detailed description of your impressive analysis.

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Thanks Karim, I hope I will be able to provide some info of value for everyone

 

Peter, I appreciate your reply! It is much because of your work that I was inspired to analyze in the way I am. In response to applying proportions, I have been working on that and it has proven difficult. Comparing katana of different schools left me very frustrated, but when I started studying just Sue Bizen school many trends of preportions started to emerge. The most clear to me is the tang almost being exactly 1/4 the blade length. But what I have found to be more reliable for placing different curvature aspects is dynamic handling. Fumbari near the machi almost always starts right where I would expect/want the static point of balance, and taper along the edge in the top 3rd of the blade always starts where I would want the center of percussion. This has lead me to believe that the smiths used these dynamic curves and placed them for the sake of adjusting handling charactoristics. I have yet to really look in to ratio of kissaki length to fumbari amount, but we know in general the longer the kissaki the less taper you have in width which makes sense for mass placement... that's the next I would like to see if there may be some rule for. Preportions in ha to shinogi are always very strict... but the closest I've gotten to that (for this school anyway) is geometrical figure matching that is a 7 sided figure started from the midpoint to the ha, but I doubt that would have been the practical way for them to measure this back then. The ratio is either 7:3 or 6:4 for this though, with most adhering to 7:3. I can link a very interesting article with information on this as it relates to different schools.

 

Kevin, I appreciate your reply as well! I have been doing some work with the steel already and am loving it. But getting it down to controlling all variables and careful hamon design is a goal for sure.

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Also important, so far I have found on every katana the ha edge of the tang to be parallel at the machi to the mune of the blade. Also, I have been very careful to study only original non shortened swords, this is very critical as shortening takes away from the funbari as well as can change relationships betweeen tang and blade.

Edited by Austin Mys
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Peter, I misread your post, and just found something very interesting from your idea!

 

These circles were derived from the approximate large circle forming the main curve. The vertical line is where I placed the fumbari transition, though may not be precise and could have been changed over the years slightly from polishing. This is too close for me to ignore!

Bizen Katana 5.jpg

 

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Peter you're a genius. I took my approximate radius measurement in inches, converted it to and adjusted to the nearest measurement in Japanese shaku (which happenned to be exactly ​7.5 shaku) and derived circles out of this. Not only does the length match perfectly, but the radius of the large circle matches perfectly, and I used the point where the circles meet to draw new lines for the fumbari and it matches perfectly. I will keep working off this.

Bizen Katana 6.jpg

 

New lines match perfectly from the 7.5 shaku radius, with the exception of a small part about 1/32" in the upper third. I'd call that within a margin for error personally.. especially on a blade quenched without clay! (editing to say this is too soon for me to attribute this to error, as many of these swords have a change in radius in this section. I do not have the knowledge yet to attribute this to happenstance or intentionality with this particular sword)

Bizen Katana 7.jpg

 

Another edit to say the next half sized smaller circle fit the radius of the kissaki except the very tip where it curves more (probably from a polisher or was forged this way, as I doubt this blade was ever fought with and damaged). I do not believe at this point kissaki were intentionally made with a complex curve, at least chu kissaki (medium length) and smaller.​ Edit: upon further study I know believe a second tighter radius is placed on purpose on the very tip of kissaki, in relation to how long the kissaki is. This reinforces longer kissaki by adding niku (meat, or curve) at the very tip as viewed from the mune (spine).

Edited by Austin Mys
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Austin,

This is absolutely fascinating!
Thank you for pushing forward with this and sharing your observations.
It is tremendously valuable and exiting to see.

The curvature of the Katana is so subtle and elusive. To see it defined like this is eye opening.

If you do not mind, I shall try your method on some other Japanese blades and see what I might find.

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Thank you Peter,

​Please do go ahead. I am curious myself to see where this goes. A part of me doubts that these radii would have been practically used by the Japanese, as many swords are much straighter than what I am studying and would involve huge circles. But at least with the sword I just did this with, the numbers seem a little too perfect to just be coincidence. There is meaning to these proportions somehow. Even if it was just a system with the older swords (which had more curve) and was later disregarded when straighter swords were desired. Or they modified the method evolved from an old system that gave them proportions to adhere to, in order to produce straighter swords? I'm curious to try this on straighter katana now.

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I've water quenched 1075 with great results. Not EVERY time but you know, thick and smoothly shaped with rounded edges, which results in a lot more grinding later. I use Parks mostly now, haven't done water in years. I wouldn't do W1,W2, 1095 in water because it would have to be much much thicker to resist cracking during the springing back/sori creating stage of the quench.

At most I've tried to replicate the look of certain swords, but not the dimensions exactly (I don't know if they're even to scale, I tend to make swords too large)

Schools and smiths had different techniques, but I think the sunobe were carefully forged with attention to thickness and taper from the machi to create the overall shape. Small differences in taper and thickness show up in the curvature after the quench.

This is really interesting... keep it going!

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Thanks for the input Brian. I originally intended on water quenching this sword, but after seeing how nice a hamon I could make with parks with this steel decided playing it safe wouldn't be too much a compromise. This being my first sword, I really don't want to crack it!

 

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Alright, I cut the tang down about 1" to proper proportion to the blade, and began scraping the scale and filing the shape after belt grinding most the scale off with a worn out zirconium belt. (pardon the blurry photo, but there's not much detail to see here anyway)

20161207_225435.jpg

 

I also started to define the yokote of the kissaki. I did this by cutting a very light plunge with a round file on the tip side of the yokote to give me a physical crisp line to follow. Then started the angled plane of the kissaki by filing the bevel at a 45 degree angle to the yokote starting from the edge up. I added a couple photos to show what this looks like. There may be a better way, but this is the only way I could figure how to do this.

20161207_213654.jpg

 

Start from here:

20161207_230912.jpg

 

Angled up away from the other side of yokote like this (exaggerated angle for clarity):

20161207_230955.jpg

 

Moving all the way up the line to here:

20161207_231017.jpg

 

Then continue filing down the face of the kissaki. Just like with western swords and knives we often make our first judgment on a maker's fit and finish quality by the guard fit, Japanese blades are first judged by the quality of the kissaki. So it is critical to get everything right here (including the shinogi remaining level as it turns back, not squished while forging like the ridge on a puukko would be)

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