In sheet metal design, the K-factor is used to calculate how much sheet metal one needs to leave for the bend in order to achieve particular final dimensions, especially for between the straight sides next the bend. Use the known K-factor and the known inner bending radius to calculate the bending radius of the neutral line. China Inconel Bends, China Inconel Bends Suppliers and Manufacturers Directory - Source a Large Selection of Inconel Bends Products at pipe bending machine ,bending machine ,metal bending machine from China Alibaba.com Aug 23, 2017 · A hole near a bend changes how the metal stretches and compresses, and that gives rise to deformation. A good rule of thumb is that any holes should be at least three times the material thickness away from the start of the bend. 5. Sheet size. The force needed to put a bend into a sheet metal piece is proportional to the length of the bend.