A nut for joining fluid conduits in a joint assembly includes a nut body having an inner body surface forming a through-bore, for supporting a first fluid conduit and a second fluid conduit. Internal threads upon the inner body surface advance in a helical path around a nut center axis between a thread origin, and a thread terminus that is located between first and second axial end faces of the nut body. At least one of the thread terminus and the thread origin is located within an increased thickness region formed by a varied radial thickness of the nut. The nut has a reduced risk of cracking in service.