If no bend allowance tables are available, how can the neutral axis of the bend be approximated?

To approximate the neutral axis of a bend when bend allowance tables are not available, the correct method is to add one-half of the stock thickness to the bend radius. This approach is grounded in understanding the behavior of materials during the bending process.

When a sheet metal part is bent, the material undergoes a change in shape, and different points within the material will experience varying degrees of compression and tension. The neutral axis is the line along which the material neither stretches nor compresses during the bending. By adding half of the stock thickness to the bend radius, you can effectively estimate the position of the neutral axis. This accounts for the material that is compressed on the inside of the bend and the material that is stretched on the outside.

This method is helpful as it simplifies calculations and allows for more accurate fabrication when precise bend allowance data is not at hand. Other options do not accurately represent the relationship between the material thickness and the location of the neutral axis in the bending process.