there is no decrease in the diameter rather the joint 58 b is formed in such a way as to fail upon a predetermined level of torque being applied to it the joint may be an adhesion such as welding soldering glue or similar adhering mechanisms excessive torque cannot be applied to the insert 14 b in that the joint 58 b which comprises a torque limiting portion will fail and further transmission of torque will be terminated the insert member 14 c in the embodiment shown in fig6 is comprised of a first threaded end 52 but no second threaded end instead of external threading formed on the exterior of a portion of the cylindrical extension 56 c a tool receiving recess 60 is formed in an end of the extension disposed away from the first threaded end 52 such recess could be a square shape a hexagonal shape a rectangular shape a star shape or other well known shapes used in driving tools other arrangements such as a shaping of an outer diameter of the cylindrical extension 56 c could also be used to provide a drive surface for the extension again a torque limiting portion 58 c of any of the types previously described is provided in the extension 56 c to limit the amount of torque that is transmitted to the first threaded end 52 of the insert 14 in each of the embodiments the insert 14 with a torque limiting portion 58 will eliminate the use of a torque wrench during installation of the tube plug 10 the described drive system with the torque limiting portion 58 will enable a mechanic to u201c torque to failure u201d thereby transmitting.