For tight rotary draw bending, maintaining a bend radius that is a whole number multiple may increase the capability of the steel bender to meet your needs. So, even though it may be possible to give a piece a 2D or 3D bend, a 3.5D bend may be more difficult because the tooling is not on hand. This type of bending is usually performed on a rotary draw bender for speed and precision, which requires specific tooling built for each bend. 2D = 4 inches, 3D = 6 inches, and 5D = 10 inches for a 2 inch diameter pipe. In these cases, the 2D would reference a centerline bend radius of two times the diameter.
For example, on a 2 inch pipe elbow, common bend measurements may be referred to as 2D, 3D, or 5D. In some instances, a rough guide for minimum radius bending would be to use a multiple of the piece diameter. A 2” carbon steel pipe will have a different minimum radius from a thin wall 2” aluminum tube. There are many factors to take into account when determining the minimum radius such as the material composition, shape, and size. In some instances, an estimator can quickly say yes or no based on prior knowledge and bending experience. Often, in the rolling and bending industry, we field requests asking about the minimum radius to which we can roll or bend a piece.
