What is the correct method for allowing for stretching on a sheet metal fitting layout with a single bend?

When preparing a sheet metal fitting layout that involves a single bend, the approach to account for stretching is critical in ensuring that the final dimensions are accurate. The correct method involves subtracting the setback from both legs of the fitting.

In sheet metal work, the setback is the distance from the bend line to the edge of the material, which accounts for material deformation due to bending. When a bend is made, the material on the inside of the bend compresses while the material on the outside stretches. To achieve the desired final dimensions, it is necessary to adjust both legs of the fitting layout to reflect this deformation.

By subtracting the setback from both legs, you ensure that the total length of the part remains correct after the bend is formed. This adjustment takes into account how the metal will react during the bending process, which is vital for producing components that fit together properly in assembly. Hence, accurately subtracting the setback from both legs allows for the proper compensation for stretching and creates a fitting that will match the intended design dimensions when completed.