US Patent 7475917 Threaded connection with variable flank angles

A threaded connection for a conduit includes a pin member and a box member. The pin member includes a pin thread having a pin thread crest, a pin thread root, a pin load flank oriented at a pin load flank angle, and a pin stab flank oriented at a pin stab flank angle. The box member includes a box thread having a box thread crest, a box thread root, a box load flank oriented at a box load flank angle, and a box stab flank oriented at a box stab flank angle. At least one of the pin load flank angle, the pin stab flank angle, the box load flank angle, and the box stab flank angle varies over at least part of the threaded connection.