Importance

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Abstract

Threaded connections are provided with a thread form that permits the construction of enlarged root radii between adjacent threads. Relatively coarse thread leads formed along conical surfaces with relatively extended tapers cooperate with relatively tall thread heights and an enlarged root radius (or radii) to produce a fatigue resistant, rotary-shouldered connection that can be assembled with reasonably attainable high torque forces. The ratios between the thread lead, measured in threads per inch, as the numerator, and denominators comprising the untruncated thread height of the thread, and/or the root truncation and/or the root radius (or radii) are maintained at low values compared to those existing in conventional prior art connections. The ratio of the untruncated thread height to the root radius (or radii) is also retained at a relatively low value as compared to that existing in many prior art configurations. The connection design produces an unexpectedly high resistance to fatigue damage or failure. The connection may be employed in any rotary-shouldered connection and is particularly effective in preventing fatigue damage in the stiffer components of drill stem assemblies including single shoulder and double shoulder drill collar connections.

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First Claim