18 has reduced in length and pulled away from its corresponding torque shoulder 20 similarly the box end 22 has pulled away from its corresponding torque shoulder 24 to prevent very low applied toques from undoing the joint after downhole expansion the locking feature l engages as a result of the expansion it should be noted that the downhole expansion could be accomplished in a variety of ways as contemplated in the present invention a swage applied pressure or an inflatable are but three of the various ways contemplated to carry out the downhole expansion as a result of the expansion downhole surfaces 26 and 28 which had been apart after makeup and before expansion as shown in fig3 move into intimate contact as shown in fig4 surface 26 is disposed on the pin 10 and surface 28 is on the box 12 these surfaces face each other and can be continuous or discontinuous fig5 shows a pattern of parallel ridges as one of the surface treatments for these surfaces and fig6 shows an alternative diamond pattern the parallel ridges are preferably oriented in alignment with the longitudinal axis of the joint the invention contemplates a wide variation of surface treatments for surfaces 26 and 28 with the desired objective being that the joint is locked together after expansion as these surfaces engage these surfaces do not need to have identical patterns that engage additionally only one surface can have a surface treatment and can engage the opposing cylindrical surface which has no surface treatment the surface treatment can be created in a variety of ways by either removing material from the surface or adding material to it the surface treatment can be.