Abstract: A well pipe connection wherein the ends of the pipes have complementary sealing surfaces and are joined together by means of an internally threaded tubular connector that engages with corresponding threads on each of the pipe ends. One of the pipe ends has threads of a pitch that is greater than the pitch of the threads on the other pipe end, and the connector threads have corresponding thread pitches. The disclosed arrangement permits the connection to be assembled to the point short of relative sliding movement between the complementary sealing surfaces on the pipe ends and final tightening is accomplished by restraining the respective pipes from relative rotation while rotating the connector to draw the two pipe ends together into compressive sealing engagement without relative sliding in order to prevent galling of the sealing surfaces.

Abstract: A hydraulic drilling jar apparatus having axially elongated outer housing and inner mandrel members that telescope relative to each other when tripped by a predetermined axial force applied to the mandrel to deliver an impact blow to an object stuck in a well bore. A negative pressure is developed within the apparatus during initial retarded telescoping movement to effect acceleration of the mandrel member upon release at a rate exceeding the acceleration rate otherwise imposed by the axial force.