Abstract: A double shouldered high torque resistance threaded connection for drill stem components having enhanced resistance to torque forces, tensile loads and material stress and fatigue is disclosed. The tool joint is provided with threads having a 75.degree. included angle between the thread flanks thereof and with generally elliptical root surfaces to minimize material stress and fatigue during operation under high torque and high tensile loads. When made up, the double intrerengaging shoulders of the threaded tool joint are in firm face to face engagement permitting torque forces and tensile loads to propagate through the tool joint in a manner that minimizes bending forces and minimizes high stress concentration so that the resulting service life of the tool joint is significantly enhanced.

Abstract: A welded pipe joint for pipes which are internally lined for carrying corrosive fluids is formed by an internally lined insert extending into the belled end sections of the pipes to be joined and engaging the belled end sections with a mechanical interference fit. The insert, which is provided with a heat shield to retard the transfer of heat during a subsequent welding operation, is held in coaxial alignment with the pipes while the adjacent ends of the pipes are brought together. The adjacent ends of the pipes are finally welded to complete the joint.