Also called laminated tubing, this type of tubing consists of two strips of coiled steel, on atop the other, rolled together in a tube mill producing, in effect, one tube inside another. Double-wall tubing is most commonly seen in the automotive industry for exhaust systems. The tooling and set-up for rotary-draw bending of double-wall tubing is the same as regular tubing except for the specification of the mandrel assembly. Because, obviously, material cannot flow from one wall to the other as it becomes plastic at the point of bend, the total thickness of the double-wall is not relevant for specifying how much mandrel support the tube requires. Instead, the thickness of the interior wall should determine the number of balls, nose and ball diameters, and the nose placement of the mandrel assembly. In other words, for purposes of mandrel specification, the inside wall should be treated as a thin-walled tube.
FREE Tube-Bending Guide Download:
A complete guide to the principles of the 4-Step set-up for tube-bending tools
This is a printable handbook showing how to implement in four standardized steps the “forward mandrel” set-up for rotary-draw tube-bending machines and establish process control over the so-called black art. The procedure is based upon the guiding principle that the tools make the bend and takes advantage of the inserted design of modern mandrel tooling.