Abstract: To fabricate a bent assembly of two metal tubes with one extending through and radially spaced within the other, the bending is done by inserting the smaller through the larger tube producing a tubular work assembly, clamping a leading work portion onto a bending forming die with the inner tube eccentric in the region to be bent against the die-adjacent inner wall portion of the outer tube, bending the region trailing the clamped portion by wrapping onto the bending die, while at (and immediately preceding) the point of feed onto the die the tubes are supported against collapse by a cylindrical mandrel in the smaller tube and a mandrel of crescent cross-section interposed between the large and small tube, in the plane of bending providing reaction support by a slideshoe bearing against the outer tube diametrically remote from the die; the mandrels being axially shiftably supported.

Abstract: A tube bending machine including a frame with a bed at one end pivotally supporting a horizontally swingable bending table bearing tube bending and clamping mechanism, including a jaw for clamping tube stock against a tube bend forming and clamping die secured coaxially at the table pivotal connection; a tube feed carriage with a rotatable tube-clamping collet for a tube to be fed to, clamped and bent at the die, the tube carriage being guided on the bed to shift to and from the said die, and free to advance during a bending operation by powered swing of the table; the die periphery having a partially circumferentially extending tube-forming groove concentric to and with groove centerline in a plane perpendicular to the pivot axis; the die and jaw each being turnable relative to the table selectably to present to each other cooperating straight grooves or cooperating curved grooves for clamping straight or curved length portions of tube to be bent, including also clamping grooves curving out of the plane of t