What is the angle of bend required to achieve a final closed angle of 15°?

To achieve a final closed angle of 15°, the angle of bend must be considered in relation to how metal bending works. When metal is bent, the angle of the bend will often create a final angle that is less than the bend angle due to the bending process itself, which takes into account factors like the material's properties and the tooling used.

In this case, bending a metal sheet to create a closed angle involves understanding that if you start with a bend angle that is larger than the desired final angle, the excess will be absorbed into the material's properties during the bending process. Therefore, to achieve a final closed angle of 15°, the initial bend must be significantly larger to accommodate for this.

The angle of 165° is the appropriate choice because when you bend a flat piece of metal to that degree, it accounts for the material's natural deformation, allowing you to achieve the required final angle of 15°. This principle is critical in sheet metal fabrication, as it ensures that the finished product meets design specifications accurately.