How can the neutral axis of a bend be computed if bend allowance tables are unavailable?

To compute the neutral axis of a bend when bend allowance tables are unavailable, the correct approach involves understanding the relationship between the bend radius, the thickness of the material, and the neutral axis itself. The neutral axis is the line in the material where no compression or tension occurs during bending.

In this case, adding half of the stock thickness to the bend radius accurately represents the position of the neutral axis. This is because, during bending, the outer fibers of the material experience stretching and tension, while the inner fibers undergo compression. The neutral axis is positioned at a point between these extremes, effectively equidistant when considering half of the material thickness. Thus, the calculation involving the bend radius and half the thickness allows for a precise determination of the neutral axis location, which is essential for predicting the behavior of the material during bending and for achieving accurate bends.

This understanding is crucial for anyone working with sheet metal structures to ensure they achieve the desired dimensions and mechanical properties in their bends. Other methods, such as simply subtracting the bend radius or just taking the thickness of the metal, do not account for the necessary relationship between these factors and therefore will not yield an accurate position of the neutral axis.