What is a K factor in sheet metal?

The K factor in sheet metal forming specifically refers to the value that reflects the deduction for bending and aids in calculating the flat pattern of the material. It represents the ratio of the distance from the neutral axis of the bend to the outer surface of the material versus the total thickness of the sheet metal. This is critical for accurate flat pattern development when preparing parts for processes such as bending, as the K factor helps predict how much material will be needed to account for the deformation that occurs during bending. Understanding the K factor allows machinists and fabricators to achieve precise dimensions and ensure that the final product conforms to design specifications.

The other options mention concepts related to sheet metal but do not accurately define the K factor. The thickness ratio and ultimate tensile strength are important properties, but they do not apply to the bending deduction process described by the K factor. Ductility pertains to the material's ability to deform without fracture, which is relevant to material selection, but does not directly inform the calculation of the flat pattern in bending.