What is this finish called?

Discussion in 'Gunsmithing Forum' started by redscho, Jul 6, 2012.

  1. redscho

    redscho New Member

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    What is the finish on the receiver of this NEF shotgun called?
     

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  2. Overkill0084

    Overkill0084 Active Member

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    Case hardening. Or "Case hardened appearance."
     

  3. redscho

    redscho New Member

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    Thank you. Is that all it is known by or are there other names for it?
     
  4. Overkill0084

    Overkill0084 Active Member

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  5. danf_fl

    danf_fl Retired Supporter

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    There a a few ways to provide such an appearance.

    One is the old way (and very few practice it). Turnbull practices the old way. http://turnbullmfg.com/

    The other involves a coating that appears like it was done the old way, but will clean off with a paint removing mixture.
     
  6. hiwall

    hiwall Well-Known Member

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    "Is that all it is known by or are there other names for it? "

    I've never really heard it called anything else.
     
  7. W. C. Quantrill

    W. C. Quantrill New Member

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    Color case hardening. It is done with bone charcoal usually, Carbon rich, oxygen starved heat.

    [​IMG]
    Here is the frame to my 44 Stevens that I just got colored again. This is the real deal. It is posted in other places, but just so you can see. I am pretty sure that NEF does color case harden their frames too. I have several and they have genuine color case hardening.
     
  8. W. C. Quantrill

    W. C. Quantrill New Member

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    They've got a good gun, too bad that they had to ruin it with the plastic forearm latch.
     
    Last edited: Jul 7, 2012
  9. W. C. Quantrill

    W. C. Quantrill New Member

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    Case hardening, or surface hardening, is done by placing the parts to be colored in a crucible with charcoal and high carbon bearing substances such as ground bone, leather, animal hooves, then the crucible is sealed shut, and brought up to a critical temperature (somewhere around 1600*) where the compounds in the crucible react with the surface of the steel to provide the colors. In the case of the 44 Stevens receiver, the receiver is stood on end and the compounds are layered in to obtain the alternating layers of colors. There is lots more to it than that, but this is the simple picture. The colors appear as a reaction of the heat and carbon in a carbon monoxide atmosphere in the crucible.