A tube and fitting assembly is made by the method of relatively moving a tube into an internal bore in a fitting with the internal bore extending end-to-end in the fitting, longitudinally compressing the tube to radially expand it into engagement with the wall of the internal bore, internally threading either the tube or the fitting and with the threads being adapted to receive a second member until it is sealed fluid-tight against the tube and there is therefore no need for a fluid-tight seal between the tube and the first fitting.