Abstract: A tube bending mandrel is provided, which is designed to avoid stress, fracture, and disassembly caused by forces exerted while a tube is bent. The mandrel includes mandrel links with a ball end, neck, and socket end, formed from two opposing and matching link sections. A radial tenon protruding from the face of one link section fits into a corresponding radial mortise formed in the face of the opposing link section. A detent mechanism includes a ball slot formed in the exterior of a ball end, a circular spring that fits into that ball slot, and a socket groove formed in the interior of an adjacent socket in which the ball end fits and rotates. By providing a ramp on one edge of the socket groove or the ball slot, the circular spring tends to move into the socket groove and ball slot, to assume a straight position after the mandrel has been removed from a bent tube. An external shoulder is provided on each socket, adjacent to the socket opening, to support a ball segment.