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Blank Blades.

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KKF Supporting Craftsman
Oct 23, 2020
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I couldn't decide whether to ask this here, or in the knife knowledge board, but chose here, because I'm planning to incorporate what I learn here into future designs (hopefully).

What I'm wondering, is if the japanese kitchen knife makers have chosen to do the "traditional" symmetrical wavy hammons on their honyakis for an aesthetic reason, or if it serves any practical purpose.

I get the purpose behind differential hardening, and I get that giving it a nice polish can look great also. What I'm wondering if the specific symmetrical wavy pattern they all tend to use (to some extent) has any practical purpose, or if they find it pleasing to the eye.

Like maybe having a the line separating the ferrite/pearlite, from the martensitic structures hard steel having that zig zag could possibly aid in toughness causing cracks to run into the soft structured steel rather than continuing through martensite.

or maybe the symmetry to the waves, and also the waves themselves could help with it not warping during heat treatment. This one I don't have as much a theory on.

Or maybe it could allow the soft steel to get closer to the edge without excess clay holding extra heat causing auto tempering?

Or is it just because it looks nice?
Now I'm very curious to this as well. Wave vs non wave hamon. Different clay patterns and different quenching. I've wondered before if it's simply a preference, or a mark of experience/ skill, or if it went beyond that and served an intended purpose/ benefit
With knives I'm sure it's purely aesthetic. I half thought on a sword it may help with toughness- differentially hardened along a straight line perhaps this adds a plane that may fracture vs a wave where there's potentially less risk in propagating a fracture? But what do I know :p
when I think about knives like Steelport that have differential hardening with no hamon it makes me think it is for looks only. Some people achieve the differential during the quench and that is more or less a straight line.
I've heard some mention of it mitigating crack and chip propagation, but nothing extremely concrete. The symmetry on the individual blade faces-how closely the clay patter lines up on each side, would/does help reduce warping to one side during the quench. The more artistic patterns we see are a fairly recent addition. If you look at the older Japanese swords, the hamons were fairly plain up until the point where the general citizenry was prohibited from wearing swords. Then it became more of a signature art form.
Thanks for the answers. It seems to be what I might have thought the answer would be. Which is a definitive maybe.

I would love to see someone with more time, equipment, money, and knowledge than I have do a study on this. Where's @Larrin when you need him?