How is the sight line on a sheet metal flat layout measured for bending?

The sight line on a sheet metal flat layout is measured from the bend tangent line to ensure that bends are accurately positioned when fabricating sheet metal parts. This measurement is critical because it refers to the location where the metal will be bent, which directly affects the part's final dimensions and its fit in assembly.

Measuring one radius from the bend tangent line allows for appropriate compensation for the bending process, taking into consideration the inside radius of the bend. The sight line serves as a visual guide that indicates where the metal should be marked for bending.

When understanding this measurement method, it's important to recognize that other options either do not represent standard practices in sheet metal layout or do not account for the natural deformation that occurs during bending. For instance, a measurement of half the thickness from the bend edge may not accurately represent where the bend should be made, as it does not account for the necessary radius, and the choice of a quarter inch from the edge lacks specificity related to the bend geometry. The measurement of two radii from the bend tangent line can sometimes be relevant for specific bending scenarios, but it does not apply universally to flat layouts, making it less accurate as a general answer.