View Poll Results: Differential or through hardened?

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  • Through

    19 43.18%
  • Differential

    25 56.82%
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Thread: Differential or through hardening

  1. #26
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    Quote Originally Posted by Michael Tinker Pearce View Post
    ...snip...
    The original question is still like, "Do you prefer peanut butter or steak?" Without context it's a meaningless question.
    Tinker,

    I like strawberries. Do you like strawberries?
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  2. #27
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    Quote Originally Posted by Tim Westover View Post
    In my opinion, the fact that with selective hardening you can get a HARD edge and SPRINGY back is just cool.

    Amazing to think they figured this all hundred and hundreds of years ago.
    The funny thing is pearlite is just soft, not springy. On the other hand, tempered martensite is very springy
    Against ignorance, gods themselves struggle in vain.

  3. #28
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    Quote Originally Posted by Bogdan M. View Post
    The funny thing is pearlite is just soft, not springy. On the other hand, tempered martensite is very springy
    Oh dear! The more I learn the less I know!
    Of course it's hot! It just came out of a 350 degree oven!

  4. #29
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    Quote Originally Posted by Karl J View Post
    Tinker,

    I like strawberries. Do you like strawberries?
    No Coke

    Pepsi

  5. #30
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    Quote Originally Posted by Tim Westover View Post
    Oh dear! The more I learn the less I know!
    Well Tim I don't know if you're serious or just ironic but after reading this thread http://forums.swordforum.com/showthread.php?t=55349 and the text on Kevin Kashen's site about the flex test I understood many things we educated SFI members take for absolute truth are still quite wrong. I just wonder what other things I consider as truth which are not...

    That said, I don't think pearlite is necessarily bad. I saw hardness tests of a real nihonto and while the edge was in the 50's HRC the core was so soft it wasn't even in the HRC scale (less than 10), it was simply soft iron. If they made it that way, they might have had a very good reason, it's just that we educated modern truth seekers don't have all the explanations yet...

    Sorry for the hijack Sam and I'll take some strawberries too
    Against ignorance, gods themselves struggle in vain.

  6. #31
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    Depends on how and in what you quench your steel in. Because you can get a fully hardened edge with a very soft spine with clay coat in water quench, or you can go fully hard and almost fully hard on the springy side on spine with clay coat if quenched in hot oil. This works well with double edged blades quenching tip first, but the hamon is not quite as vivid as the water quenched. It is still differential heat treat. I think I preffer it for double edge swords due to the fact that the spring is there the toughness is there and the hardness is there, plus it's pretty toooo! Gotta be done just right and the polish is a beouch! Alot of the old chinese jians were done this way and they were thin double edge blades with hamons and were alot of times very springy. SSssoooo smith smith smith, but yeah I choose differential hardening, but dangit, I love a good through quench oh well guess I'm just vague. Hey Sam you never said which you preffer, I think I know
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  7. #32
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    Quote Originally Posted by Bogdan M. View Post
    Well Tim I don't know if you're serious or just ironic but after reading this thread http://forums.swordforum.com/showthread.php?t=55349 and the text on Kevin Kashen's site about the flex test I understood many things we educated SFI members take for absolute truth are still quite wrong. I just wonder what other things I consider as truth which are not...

    That said, I don't think pearlite is necessarily bad. I saw hardness tests of a real nihonto and while the edge was in the 50's HRC the core was so soft it wasn't even in the HRC scale (less than 10), it was simply soft iron. If they made it that way, they might have had a very good reason, it's just that we educated modern truth seekers don't have all the explanations yet...

    Sorry for the hijack Sam and I'll take some strawberries too
    Hi Bogdan, I should have said, "not hard" instead of springy. I have been rereading all my heat treating stuff as I never was very good at naming martensite, pearlite, etc.

    Somewhat on the subject, I've heard of sensei straightening Nihonto over their knee after a bad cut. Also in the early 90's I read an article in some magazine where they were testing swords. They took a Don Fogg blade and duct taped it side up between two saw horses and then hit it with a 2x2. It bent and held the bend. The reviewer then said that it was a bad sword because "a bent sword can't cut". Personally I'd rather have a bent sword than a broken one.
    Of course it's hot! It just came out of a 350 degree oven!

  8. #33
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    That could be one explanation, many people also mention shock absorbtion, but I haven't seen any theoretical/scientifical model explaining how it works.

    It is also true that well made Japanese style swords are differentially hardened, but you can find more then 2 tempers of steel on the same blade, the simplest structure being hard edge (hard martensite), springy middle part (tempered martensite) and soft pearlitic spine. This without taking into account the differences occuring at different depth in the steel and the different varieties of martensite that can be obtained (lath, plate) by using steels with different carbon contents through lamination.

    A good differentially hardened blade has a very complex and performant structure, I just chose TH as a much safer bet, less complex thus less likely to go wrong. If we make the assumption we're talking about a skilled smith I'd definitely pick DH...
    Against ignorance, gods themselves struggle in vain.

  9. #34
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    Me, personally... I like differentially tempered... Sort of related to through hardening but achieved selectively in the tempering stage rather than quenching phase. Ofcourse, that is based on performance and not aesthetics.

    Seems like there was a discussion a year or two back on here somewhere about yield strengths and structure that was quite worth reading through for a metallurgical view of this stuff....

    Or to put it another way, there is more than one way to skin a cat... And I like to have more than one option in my toolbox to work with...

  10. #35
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    OK, Scott just when I think I'm getting a handle on all this,in a joe sixpack shallow kind of way,you gotta throw differentially TEMPERED into the mix.One more thing for me to look up.Gotta love it.Thanks

  11. #36
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    Quote Originally Posted by Scott Byler View Post
    Me, personally... I like differentially tempered... Sort of related to through hardening but achieved selectively in the tempering stage rather than quenching phase. Ofcourse, that is based on performance and not aesthetics.

    Seems like there was a discussion a year or two back on here somewhere about yield strengths and structure that was quite worth reading through for a metallurgical view of this stuff....

    Or to put it another way, there is more than one way to skin a cat... And I like to have more than one option in my toolbox to work with...
    Trouble with Differential temper is that, unless you can keep the edges cool and the spine very hot you are doing nothing but spoiling the hardness. Guess ya gotta know what you are doing again
    "Ah, the old disco room.......just as I left it!" Cassanova Frankenstein

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  12. #37
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    Quote Originally Posted by John Lundemo View Post
    Trouble with Differential temper is that, unless you can keep the edges cool and the spine very hot you are doing nothing but spoiling the hardness. Guess ya gotta know what you are doing again
    Unless you have access to induction. Then you do it backwards. Temper first, then harden.

    ALTHOUGH......

    I've looked at some good, flexible heat sinks, designed for quick chilling. I don't have the time to try them out on a sword edge though.
    Jim Frank has been looking into this also...
    Barnyard bladesmith, burnt in the front, and frozen in the rear. Comic book metallurgist, too dumb to know that I can't do that.
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  13. #38
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    Quote Originally Posted by John Lundemo View Post
    Trouble with Differential temper is that, unless you can keep the edges cool and the spine very hot you are doing nothing but spoiling the hardness. Guess ya gotta know what you are doing again
    Yessir, it takes some practice and real care. But, done right, it is a technique that sort of bridges the differential hardened piece and the through hardened...

    All in all, though, the more I know the less I'm sure of in smithing... lol

  14. #39
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    w00 w00, through hardening for the win! Haha

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