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Internal thread tensile strength

  1. May 3, 2012 #1
    calculation of internal thread tensile strength

    Hi All!
    I've got a coupling device that has two internal threads of different pitch, length, diameter. The smaller thread takes a lifting bolt, the larger attaches to a piece of machinery.
    I've been asked to work out the safe working load (SWL) limit of the coupling. I have the lifting bolt and thankfully it is stamped by the manufacturer and so I've been able to easily calculate it's maximum lifting capacity.
    What I need help with is working out the maximum load that can be applied on the internal threads of the coupling device in pure tension.
    To make it harder I don't yet know the material of the device or the thread and pitch of the largest internal thread, but I'm working on it!
    Can anyone suggest a good method for the calculation? It does not need to account for shear forces, pre-load or torque. The coupling is hand tightened and lifted purely along it's axial line.

    Attached Files:

    • Jig.jpg
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    Last edited: May 3, 2012
  2. jcsd
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