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  1. #1
    Boringgeoff is offline Try not to be late, but never be early.
    Join Date
    Apr 2011
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    Default Technical query.

    Over on the WW Forum, Hand Tools -Unpowered - unusual brace, we were talking about a brace patentee Nelson Spoffard and a statement he made in an 1880 patent.

    A patent update in March 1880 (US Pat 22768) Spofford rejects sawing the division in favour of casting it forked because "to preserve the strength and resiliency of an article made of cast metal it is necessary to preserve the skin of the casting intact, as the thin hard covering or skin that envelops the casting has the effect of imparting increased strength to the same. Hence, when the slit is formed in the arm of the bit-brace by cutting the metal away with a milling device, the interior portions of the arms are left without the skin metal that surrounds the outer portions of the arm, and thus the slitted arms materially weakened and their resiliency lessened to a considerable degree".

    How accurate would you foundry aficionados think this statement is?
    Cheers,
    Geoff.

  2. #2
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    Default

    Basically any introduction of a sharp internal feature will always be a concentration for stresses. I think its more the inherant radius in the casting than the actual skin which is providing the strength.

  3. #3
    Join Date
    Dec 2007
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    Default

    I agree as far as rads go in any casting.
    Cast iron certainly has a hard skin and Spofford braces were CI.
    So maybe a bit of both?
    H.
    Jimcracks for the rich and/or wealthy. (aka GKB '88)

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