Which measurement should be subtracted from the mold line length to determine the length of a flat in a sheet metal project?

The length of a flat in a sheet metal project is determined by subtracting the setback dimension from the mold line length. The setback dimension indicates how much material will be lost due to the bending process. It accounts for the area that will be bent and helps ensure that the flat piece ends up being the correct size after it is bent into shape.

When creating bends in sheet metal, the mold line refers to the theoretical line that runs along the center of the bend. The setback dimension represents the distance from this bend line to the edge of the material, which must be considered to avoid producing a final part that is too long or too short. By subtracting the setback dimension from the mold line length, you arrive at the correctly calculated length of the flat piece before bending.

Other factors like the bend radius, bend allowance, and total thickness of the material do play a role in various aspects of metalworking and bending calculations, but they do not specifically determine the length of the flat in the same way the setback dimension does.