Sheet-metal development
Why bend allowance follows the neutral axis and why approved bend-test data controls production blanks.
ENGINEERING PRINCIPLE
Material on the inside and outside of a bend changes length differently; the neutral-axis length is used for preliminary development.
BA = θ(R + Kt)Variables and units
- θ in radians
- R and t in mm
- K from approved bend data
Worked example
At 90°, R = 3 mm, t = 2 mm and K = 0.33, BA = 5.75 mm for that bend.
Conditions and reference
Formula and displayed units independently checked for the stated conditions. This is not a code-compliance design method.
Source: J. G. Bralla, Handbook of Manufacturing Processes; verified bend-test data supersedes generic K-factor guidance.