FATIGUE RESISTANT THREAD PROFILE WITH COMBINED CURVE ROUNDING
A threaded connector that includes a pin end having external threads and a box end having internal threads that are complementary to the external threads has a thread profile that defines at least a portion of either or both of the internal threads and the external threads. The thread profile may include a thread root connecting a first flank to a second flank and the thread root may be at least partially defined by a plurality of tangentially interconnected radii. The plurality of radii may include at least a medial radius, a first distal radius on one side of the medial radius, and a second distal radius on the another side of the medial radius. The medial radius may be larger than the first and the second distal radius. Alternatively, the thread profile includes a thread root connecting a first flank to a second flank that is at least partially defined by a plurality of radii, each radius having a different length and each defining a circular arc.