A unit of radial measurement peculiar to tube-bending. “D” is the ratio of the centerline radius to the nominal, not the true, outside diameter of the material: “D” = CLR / nominal TOD. This distinction between nominal and true diameters is critical when “D” of bend specifies the centerline radius of a pipe (as opposed to a tube) bend, because pipe diameters by definition are identified by nominal values. For example, the centerline radius of a 3-“D” bend of a 2″ IPS pipe (which is 2.375″ true diameter) is 6 inches instead of 7.125 inches.
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.