Described is a chromatographic column assembly that includes an outer tube comprising a metal, a first conduit disposed within the outer tube, a second conduit disposed within the outer tube, and a first joint located between the first conduit and the second conduit. The outer tube is deformed by a first uniform radial crimp at a longitudinal location along the outer tube that surrounds the first conduit on a first side of the first joint, and a second uniform radial cramp at a longitudinal location along the outer tube that surrounds the second conduit on a second side of the first joint. The first and second uniform radial cramps form a fluid-tight seal between the first conduit and the second conduit and each have a substantially flat base region over which a diameter of the outer tube is reduced for a non-zero longitudinal length.