What are the two critical calculations involved in bending sheet metal?

In sheet metal fabrication, two critical calculations are bend allowance and setback.

Bend allowance refers to the amount of elongation that occurs in the material during the bending process. It accounts for the additional length that must be added to the flat layout of the sheet metal in order to achieve the desired angle after bending. This calculation is essential for ensuring that the final dimensions of the part are accurate.

Setback, on the other hand, is the distance from the bend line to the tangent point of the bend. It is important because it helps determine how far from the bend line the material must be cut to accurately account for the bend, ensuring the final part meets design specifications.

Both bend allowance and setback are fundamental to creating parts that fit together correctly, enabling the manufacturer to predict how the metal will behave during and after the bending process, and to ensure that parts will fit together once assembled.