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  1. #1
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    Wootz, Roselli UHC, and My Oven

    After reading this review and the associated comments about chipping and tip-breaking, and the description on Roselli's site of a hardness of ~65 HRC, I'm wondering why the UHC blades are so hard and brittle?

    My understanding is that the UHC blades are a type of modern Wootz. However, Wootz steel is supposed to be soft with the very hard carbides doing the cutting– like the "diamonds in pudding" metaphor. Then why does Roselli harden them so much?

    Also, I'm wondering if someone could use his kitchen oven to temper the blade a bit softer/tougher, like you can with a file?
    The strength of the pack is the wolf.
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  2. #2
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    Re: Wootz, Roselli UHC, and My Oven

    Harder steel keeps a very, very sharp edge for longer, IF you can stop it from chipping.

    In my own opinion, anything over RC60 or 61, depending on the steel, is just asking for trouble.

    Yes, in theory you could re-temper the blade and bring its hardness down a bit, however, the variables in household ovens do not lend them to accurate heat treating and without knowing the exact steel type used you would be playing a guessing game anyway. Household ovens (all ovens actually) bounce well over the target temperature then drop back after a while, then bounce over again, and so on and so forth, in a continuing cycle. Commercial heat treating ovens keep this to a minimum but you still need to be very careful when approaching your target temperature so as not to overshoot.

    I don't think it would be worth the time and effort after buying the knife to have to remove it handle and faff around with the blade to soften it. It's possible, but fraught with potential problems.

  3. #3
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    Re: Wootz, Roselli UHC, and My Oven

    Quote Originally Posted by Judas
    After reading this review and the associated comments about chipping and tip-breaking, and the description on Roselli's site of a hardness of ~65 HRC, I'm wondering why the UHC blades are so hard and brittle?

    My understanding is that the UHC blades are a type of modern Wootz. However, Wootz steel is supposed to be soft with the very hard carbides doing the cutting– like the "diamonds in pudding" metaphor. Then why does Roselli harden them so much?

    Also, I'm wondering if someone could use his kitchen oven to temper the blade a bit softer/tougher, like you can with a file?
    My suspicion is that Roselli are describing an RHC “equivalent” hardness, rather than the actual test results from a punch test. A proper Rockwell test is irrelevant for this type of “wootzy” steel; as it is for Talonite for example. The Carpenter is intended for wood carving and general woodwork. I have used one of these blades and it performs extremely well without chipping.

    I think it would be very unwise to try messing with the temper of such a blade. Either you accept that Roselli know what they are doing with this type of material, or you might be better buying a different knife/blade.

    Rules of thumb are nice things, to avoid having to think everything through from first principles. So RHC 61-63 for the centre of a laminated wood-carving blade, RHC 58 for a general utility knife, RHC 54-56 for a hard use hunting knife that will hit bone, are nice general approximations, but they don’t mean a lot when the steel is radically different to normal. Old Japanese swords using really Ultra high carbon steel edges often have absurdly high RHC, but they seem to have worked ok..

    Have fun

    Mike

 

 

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