to metal seal is in the contact location for the fingers 32 and 34 along their sidewalls as they retain the expanded thread together whether it is a single step thread or a multiple step thread the presence of the restraint that provided a metal to metal seal and allows for relative axial movement is applicable both at an end or both ends of a thread form as it is between steps of a multi step thread form referring back to fig1 the box 10 has a taper 52 on its exterior located just below the lower end of thread 14 pin 12 has a taper 54 about even with its finger 34 those skilled in the art will appreciate that these tapers increase the wall thickness and are placed there to control stress concentration and to influence the fingers 32 and 34 to flex during expansion so that their respective longitudinal axes while remaining aligned with respect to each other are both skewed with respect to the longitudinal axis 56 of the connection this skew angle of preferably under 15 degrees adds a component of force normal to the longitudinal axis of the fingers 32 and 34 to push them together and enhance the metal to metal seal that is between them the skew helps to maintain seal contact during or after expansion or increase break out torque during or after expansion those skilled in the art will also notice by comparing fig1 to fig2 or 3 that the finger tips as a result of expansion and relative axial movement induced by radial expansion have pulled away from the opposing bottoms of grooves 36 and 50 while holding some finger overlap to help maintain the metal to.