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Post by izzy on Dec 7, 2023 9:10:25 GMT
Speaking from 2 examples I have/had Legacy Arms seem indeed to be slightly softer towards the middle, but it does not go deep, where a fuller is ground in, the metal is equally as hard as the edge, never thought this was intentional since it is so slight. I wonder if "Grind Hardening" could be an explanation for that?
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Post by mrstabby on Dec 7, 2023 9:37:31 GMT
The difference is minimal anyways, the lower hardness sections are low 50HRC, the edges are slightly softer than 55HRC. I can only estimate this with other stuff I have where I knoiw the HRC, so it's by no means accurate, still the difference isn't that big.
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Post by izzy on Dec 7, 2023 10:05:04 GMT
The difference is minimal anyways, the lower hardness sections are low 50HRC, the edges are slightly softer than 55HRC. I can only estimate this with other stuff I have where I knoiw the HRC, so it's by no means accurate, still the difference isn't that big. 55 HRC is not too bad for an edge. 50 HRC is the lower end of usefulness for a sword edge, but pretty good for the middle part, hard enough to resist bending, low enough not to break. The issue may be 5160 itself as a "deep hardening" steel might be hard to get a true differential temper where the spine or center is very soft.
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Post by mrstabby on Dec 7, 2023 10:46:29 GMT
Need to revise my statement, had the wrong card, edge is 52/53HRC (slightly harder than Windlass), raised parts are 50HRC (as hard as Cold Steel machetes). It's a minute difference really. Feels like only the raised portions between edge and fuller are slightly softer, more like a San-Mai than a differential hardening. I am just not sure if this is really something that would add much to the blade's strength, specifically because most real DH blades are closer to 60 on the edge and 40 on the spine (I think).
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Post by larason2 on Dec 7, 2023 14:02:49 GMT
My understanding with deep hardening steels like 5160 is that they still temper them after the hardening. That means they are harder in the centre than a shallow hardening steel, but still not as hard as the surface.
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Post by mrstabby on Dec 7, 2023 14:34:25 GMT
AFIAK that's not so, it should be pretty equal all the way through (unless the blade is very thick, like over 15mm/0,5"), of course you could if you don't let the part soak long enough in the oven after quenching. 1095 hardens to a debth of 0,08", so you could use a 0,16" blank and still get the same hardness all the way through (according to knifesteelnerds info).
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Post by larason2 on Dec 7, 2023 22:54:46 GMT
I suppose you're right. The tempering does reduce the hardness from its maximum though, and as you say, for the typical thickness of swords or knives, it's pretty much hard all the way through. Still, I don't think this will affect its performance in any way vs. differential hardening, provided what is being stressed is the hardened part. If you try to break a DH sword on the softer spine, it will in theory break easier than a TH sword. In practice, I don't think you'll really see that though. As you say, for most sword diameters, even shallow hardening steels harden all the way through. The hardened/tempered steel has similar properties to softened steel for most respects, though I can concede resisting getting a set would be different. Probably wouldn't matter to most people though.
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Post by darknovashin on Dec 8, 2023 1:08:17 GMT
For Japanese blades, the Kogarasu Maru is the classic example, and the shape can be called Kissaki Moroha Zukuri. The sword is in the Imperial Family's collection and is thought to represent the transition of double edge to single edge blades. It's been copied into other blades over time as well. In modern manufacturers, Bugei, Hanwei and Cloudhammer have all done versions of this shape over the years, but it's not a commonly manufactured option. It's likely both allot more work to temper and sharpen. Might be able to find them second hand though.
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Alan Schiff
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Post by Alan Schiff on Dec 11, 2023 18:53:19 GMT
IIRC Tinker did a number of differentially hardened swords before he stopped making longer blades. I don't know what method he used. I also believe I've seen some from smiths that specialize in migration/viking era swords, but don't remember who offhand.
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