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Meet the Couple Photos: Elements of Our Wedding: Outline Logistics: Registry |
Flatenning the Billets  Because metals have a tendency to 'spring back' from bending, it had to be bent beyond straight so that it sprang back to a straight billet. This had to be repeated for every little kink, on both billets one at a time. The jaws of the milling machine were very flat, which helped not to put any dents in the billets. 
Materials can undergo two modes of deformation - elastic and plastic. Elastic deformation
is non-permanent, and plastic deformation is permanent. If you were to stretch a spring, and it sprang
back to its original shape, then that is all elastic deformation. However, if you stretched it further,
it would get partially bent out of shape. That permanent change is plastic deformation. When a material is stressed, it first
undergoes elastic deformation. If it does not reach the yield stress, or the stress where
plastic deformation starts, then it will completely spring back. If the material is stressed beyond the
yield point, it will permanently deform. The elastic part of the deformation will spring back once the
stress is taken away, leaving only the plastic part remaining. That is how the gold was straightened in
this step.
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