Fastener Thread Tensile Area of External Thread Equation and Calculator

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When a standard ISO threaded fastener fails in pure tension, it typically fractures through the threaded portion (this is characteristically it’s smallest area). For this reason, the tensile stress area is calculated through an empirical formula involving the nominal diameter of the fastener and the thread pitch.

Tensile Stress Area of an external thread (fastener, screw)

A t = 0.7854 ( D 0.938194 P ) 2


At = Tensile Stress Area, mm2
D = Basic Major Diameter, mm
P = 1 / Number of threads / mm

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