Abstract: A tube fitting with a one-piece ferrule adapted to shear during assembly into two cutting rings for serial setting of the cutting edges thereof into the tube surface. The rear cutting ring is deformed and guided by the previously set front cutting ring at a preferred cutting angle. Engagement of abutment surfaces on the cutting rings determines a final position for the rings and provides a signal to the assembler that the joint is completed. The undeformed ferrule includes a conical front cutting ring having a cutting edge of one diameter, a cylindrical rear ring having a cutting edge of larger diameter, an external annular groove and an enlarged bore therebelow which in part forms the rear cutting ring and controls deformation thereof. The annular groove is placed to define a shear zone between the cutting rings and the shoulders of the groove are the abutment surfaces for determining completed joint position.