mas4t0

Hi Austus, I will be applying niku to the models, but I need mathematically actuate basic geometry for the foundation. As I won't be able to get an accurate understanding of the nature of the niku on each blade, I'll be applying the same level of niku to each (the actual thickness will be proportional to the edge angle described above). So I won't be eliminating it from the tests, but more eliminating it as a variable, if you see what I mean. I could do a purely theoretical analysis, and determine the optimal angles and geometry for a given metallurgy and heat treatment when subjected to particular usage cases, but I'm more interested for now in a more empirical analysis of historical blades. If it was purely theoretical, the optimisations would be responses to the criteria I (somewhat arbitrarily) set rather than anything particularly representative of real world usage. All things being equal, a hira zukuri will cut the best on a soft target, but it is also going to perform the worst in the event of an off angle cut, be the weakest laterally and the most prone to chipping. There's also the issue of how to weigh the variables, many of which are mutually exclusive and therefore a comprise. The analysis should show it up, but I think that the different blade geometries are more different than they at first seem. I think that the analysis will clarify my meaning to a greater extent. That's just a long way to express, that I think there is a lot more variation than meets the eye. I'm glad to see we're on the same page, I think we may have had crossed wires earlier. Thank you for your input, and if you have any other thoughts, please let me know. Regarding scanning; I don't have any expertise with this. I don't know if it would be possible to get an accurate scan of a curved and polished surface, but it's certainly beyond my capabilities. Mark

Thank you Jacques. In that case, I'll probably start with the Shinto set and go from there. I'm planning to create 3d models of various blades in CAD software so that I can run some simulations on them and assess their handling dynamics and strength characteristics. Is the text for the dimensions quite formulaic between swords? I don't understand Japanese, but have several friends who do, so I would be able to get translations for any common terms.

Thank you Jacques. I think I'll order one of the 3 volumes for the moment. Do you have a recommendation on which to start with? Thank you. Mark

Hi Jacques, Could you please let me know which book that is? Does it provide those measurements for most of the blades included or only a few? Thank you. Mark

Thank you again Ken, that's good to know.

Do any referance books give the dimensions of the thickness of the blade at the shinogi and the mune in addition to the other dimensions?

Thank you Ken. Those are a great help. I have one more question on this topic, and I'll try to keep it from being too open this time. I can't tell from context if the cross-sections in this image are actual cross-sections or are imagistic representations. Would you consider the cross-sections to be at all representative in terms of the geometry?

Thank you Ken, sorry about the barrage of questions, your guidance is much appreciated. I'll be looking over the paper with great interest.

Hi Austus, I'm not meaning to truly consider blades without niku, but trying to simplify the geometry for the moment so that I can understand the basic angles involved and the nature of the cross section. With niku, we have a convex edge with varying angles as we transition from the ha to the shinogi. I would consider the angle (without niku) to be the primary angle and the niku to be a convexity applied on it (from a geometric perspective). I'm also presuming (quite likely incorrectly) that the effect of healthy niku should be somewhat systemic, and proportional to the angle 'θ' shown above; therefore for the sake of comparison we can disregard it. With niku it gets very complicated. This way, all I need to take account of is the thickness at the shinogi and the height of the shinogi from the ha; from there it's basic trigonometry. I think the 'drag' is more an effect of the broad edge angle causing wedging rather than directly caused by the shinogi itself. I imagine that you would experience similar amounts of 'drag' in all the lower cross-sections, if anything, the cross-section on the lower right (representative of a hira zukuri) would have the most as it is thickest at the mune and would be diverting the most force (of the three) to spreading the target. I would be very interested in learning about the properties of the hyperbolic ha-niku and the parabolic hira-niku, but they would require equations just to define them properly. Mark

Hi Ken, Thank you for the information. I'm trying to get a grasp on the geometry. While the measurements would be different for each blade, is there some consistency in the proportions of the cross section? Would you say that in response to their experience during the Mongol invasion that the blades were scaled up proportionally in all dimensions, or that there was a transition to a more hexagonal cross section (as shown in the leftmost diagram) which I believe would make the blade stronger in torsion and shear? If we ignore niku, and consider a straight line directly from the shinogi to the ha, is there any consistency in the angle? I realise it would be different for hira zukuri, shinogi zukuri and shobu zukuri; but would they be relatively similar (within a few degrees) within the same category? Would you ever see as in the bottom image, where the edge angle is the same across different geometries? Thank you. Mark

Are there any commonalities in the thickness of blades at the mune and the shinogi? Is there some consistency within schools, or is it rather idiosyncratic to each blade?

I just watched this one. £1.2 million for about 50g of rusted iron from the hull of the Titanic! Considering that they've pulled up well over 15 tonnes of the stuff, does that put the total value of the hull at £360 BILLION?!

I've been admiring this koshirae for quite some time now, but I can't seem to find any other examples which are similar. I'd really like to know if this is indicative of any particular time period or region, or if it is simply a variation. I am intending to have a blade mounted in a similar style and I would be very appreciative of any opinions as to what style of tsuba you think would be appropriate. Unfortunately, this is the only picture that I have, it has been saved on my computer for a long time and I don't any longer remember the source. Kind Regards, Mark H

Nah, you need a bo-staff for that. :lol:

I was pretty much thinking out loud, I'll stop now.

Thank you John it's most appreciated, I've looked for something like that for a long time. Tamahagane seemingly has a Vanadium content of 0.015%, I would expect that you'd need about 10x as much for it to be significant as an alloying element.

I apologise Ken, I honestly wasn't aware of that, though I would be VERY interested to see a chemical breakdown. I've never come across steel produced here in the UK where there is more than trace amounts of Vanadium, unless the steel has been actively fortified with it. On the other hand, having random alloying elements within the steel is far from ideal. I may be missing something, but I for one would not be inclined to spec titanium as an alloying element for a steel I was intending to produce swords from. Likewise, as far as I'm aware, Silicon is only useful for low carbon steels as it helps prevent porosity; and it is generally actively removed as it is considered an impurity.

Well Alex, as strange as it may seem in light of all I've just said, I would have to agree with you, at least for the better nihonto! Using a metallurgically superior steel is no guarantee of a superior blade; the superior steel simply has more potential. I would always vouch for an expertly heat treated traditional blade over an inexpertly heat treated blade constructed of modern steel. The magic is entirely in the heat treatment. While a modern tool steel would massively outperform a tamahagane blade if the heat treatment on both was perfect; the fact of the matter is that the heat treatment of a factory produced blade is never anything close to perfect. For one they're heat treated in batches and secondly, even if the heat treat were done individually by a smith, unless he has worked with that particular steel for an extended period and has truly mastered the heat treatment, the results wouldn't be much better. There are actually a series of super premium alloys (used primarily in kitchen knife making) which are produced by Hitachi (called Aogami Super Steel). They produce two families, known as White steel and Blue steel (due to the paper that they're packaged in). On paper blue steel greatly outperforms white steel, but the vast majority of manufacturers shy away from it; the reason being that white steel is much more forgiving in terms of heat treatment. Perfectly heat treated blue steel will outperform anything else out there, but if the heat treat is slightly off, the results are very disappointing. White steel on the other hand produces a fantastic knife even if the heat treat is a little off.

I'm sorry Remy.

That is pretty much a null point with modern metallurgy. The issue isn't the balance of hardness and softness, but the balance of brittleness (which is a function of hardness) and ductility. It's just that hard and soft are pretty good indicators of brittleness and ductility. The features of the Japanese blade which make it so special are mostly solutions to problems which only arise due to the crudeness of tamahagane! The lamination was necessary because the marquenched tamahagane was simply too brittle and the ductility of iron was needed to give the blade resilience and toughness. In the case of modern steels, Martensite is often the hardest, toughest and most resilient microstructure and the balance of hardness to toughness is determined by the temper. As an example, ALL steel aerospace components are entirely Martensite. A lot of those components have no need for hardness, and their resilience is the single most important factor. To weld a softer core to a suitable modern steel would do nothing to help as the softer iron/ steel would likely not be as tough as the outer layer of Martensite; and even if the non-martensitic core was tougher (which isn't the case with any alloys that I'm familiar with) you'd still be introducing a grain boundary which would compromise the overall structural integrity by a much greater amount than you'd have gained.

To compare modern steel to tamahagane is really an apples and oranges comparison. In a tatara the steel in never completely molten so there is never a time during smelting where you are able to remove impurities chemically; and there is only so much you can do by forging. Consider a large block of salt contaminated with some sugar (99% salt 1% sugar); it will be virtually impossible to mechanically remove all but the largest inclusions of sugar; this approach is akin to the traditional process. Now consider that you can simply dissolve the whole thing in water and then recrystallize the pure salt and pure sugar separately; this is akin to the modern process.

I can go look through some of my books if you'd like some more exact details, but I believe that steels pretty much on par with today's 10xx series would have been available since the mid 19th century. The BOS (Basic Oxygen Steelmaking) process used today wasn't commercialised until the 1950s; there were however other methods available for about a century prior to that, they were just more expensive and more labour intensive. In reality, once you're able to maintain a high enough temperature to keep it completely molten, it becomes an issue of quite basic liquid chemistry; in essence the molten steel contains all the impurities in solution, materials are added to react with the impurities and to precipitate them. The main impurity is Silicon, for which Calcium is added, this forms Calcium Slilcate (Ca2SiO4) aka Slag, which collects at the bottom of the furnace and can be tapped off separately and discarded. Alloying elements (such as Vanadium) can be added to the moltern metal and dissolved into the solution. None of the chemistry has changed since it was first done in the 1850s, it's just that steel can now be produced far cheaper, on a far greater scale and more advanced/ specialised alloys have been developed. I'm not sure how Japan's facilities and metallurgy were during the 20th century (Hitachi now lead the world in a number of ultra-high end steels); but their European allies would in any case have been able to provide them with high quality steel (at least in the run up to the war).

In short; because the perception of high quality has shifted due to there being much higher quality steel available today. 10xx series steels are cheap and are relatively low grade by modern standards; however an equivalent steel to tamahagane such as 1086 (that's straight carbon steel with 0.86% carbon) is significantly cleaner (less impurities) and if properly heat treated would have greatly improved material properties. To keep that in perspective, 1086 is a cheap steel, tools steels such as W1, W2 and L6 are fine tuned to their specific application, far cleaner and are fortified with alloying elements. Through folding, the impurities are driven out; but only up to a certain point. Flux is not used in nihonto manufacture as the impurities themselves serve as flux; it is therefore imperative that there be a certain amount of impurities in the steel in order to prevent weld flaws.

Strength, durability, resilience and toughness are all measurable physical properties which can be looked up on a database, in order to enable Engineers (such as myself) to determine which material is best suited for a given application. As an example, the addition of a tiny amount of Vanadium (approx 0.2%) will significantly increase the strength of the steel; tamahagane of course does not have this. Modern steels are in a completely different league to tamahagane from an engineering perspective; due to there being much fewer impurities (such as Silicon and Phosphorus) and the addition of useful alloying elements (such as Vanadium and Manganese). I'm curious where the idea that a monosteel would be brittle has arisen. On that basis, would you assume that all springs are constructed of laminated steel?

It's important to take account of advances in metallurgy. A mono-steel blade forged from a high quality modern steel will be significantly tougher and more durable than any traditional blade (regardless of lamination). That is of course assuming that the heat treatment is done properly. This video shows a mono-steel blade produced from a modern tool steel (L6), with which edge holding and wear resistance are compromised in exchange for virtually unparalleled toughness and durability. https://www.google.co.uk/url?sa=t&sourc ... 3672,d.d2k I can't give any specifics on gunto, as I have no idea which alloy was used.