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Re: [Orchid] State of casted rings?
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Peter W . Rowe Monday, May 02, 2011
   
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Joy,

>     I will tumble all of these rings and I am assuming that will work
>     harden them slightly and reduce some of that porosity but is it
>     ever the same as a forged ring? 

    Tumbling affects only a thin surface layer, perhaps a half
    millimeter deep at best, and that's with steel shot, not with the
    tiny pins of a magnetic tumbler. They don't do much at all beyond
    surface brightening. With heavier steel shot in a decent rotary
    tumbler, the work hardening that occurs is still only the surface
    layer, and not to a large degree in terms of affecting the whole
    ring. The main effect is that by burnishing the surface, the tumbling
    allows that surface skin to be a bit more compacted and free of
    obvious surface porosity, thus a better polish than what you get with
    just plain cast silver. But then, only if, when polishing the tumbled
    ring, you can do it without cutting through that thin burnished
    layer. It's thin enough that this can be uncertain. While such a
    surface can be slightly tougher and more resistant to scuffing and
    tiny dents, the overall toughness of the ring, resistance to bending
    or breaking on a stretcher, or even the degree to which impacts will
    cause the larger size dents, will not be significantly different from
    the plain cast ring. This is not to say tumbling is a waste of time.
    It isn't. It does distinctly help, and improves the surface sometimes
    quite a bit. But don't expect it to do much more than that. It's
    still not even close to a forged ring, because 99 percent of the
    silver remains in the as cast state, rather than with the tight,
    uniform, small crystal structure that a properly treated forged piece
    can have. There is still, as you've noted, a large difference. 

Peter

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