> From memory. A thread is considered a cantilever beam, with a point
> load applied at the middle of the span, and the section properties
> taken at the middle of the span. Pitch diameter is midway between
> the major diameter and the minor diameter.
Not quite accurate. The convention is that the bolt or screw
(external thread) fails in tension at the OD of the 'stress area.'
The stripping failure mechanism of the internal thread is shear
across the pitch diameter. You can also calculate a load for
stripping the male thread in the event that the screw or bolt is
weaker than the internally threaded element. Machinery's Handbook has
formulas for calculating these failure loads. You can find pdfs of
federal Standard H28 on line with a quick Google search
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/members/chrisw/
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