However, when materials undergo plastic deformation, as they do in bending operations, the neutral plane does not remain at the center of the sheet. The bend allowance ( B a) for outside measurements A and B is related to bend length ( B L) by: If not, they can be used with data from a simple test bend to determine the material properties, and then applied to the bend at hand.įinding bend length: If the material bends with the neutral plane in the exact center of the sheet, bend length ( B L) can be calculated from: If the material’s strength and ductility are known, the equations can be used directly. Even if they were, the required stock length depends not only on end radius, material thickness, and angle of bend, but also on the specific material being used.įortunately, there is a series of equations that are valid for all materials that can calculate bend allowance and bend length. But these methods are unavailable to some engineers. When engineers need to make curved or bent pieces of sheet metal, they use company-written tables, rules of thumb, and guesstimates to determine the length of straight stock needed for bending into a precisely measures curved part.
