Bend allowance vs bend deduction: which formula to use when

Outline

• Define bend allowance as the arc length through the neutral axis.
• Define bend deduction through outside setback.
• Explain inside flange dimensions vs outside flange dimensions.
• Walk through one single-bend part and one common mistake.

Internal-link targets

• Bend allowance calculator
• Bend deduction calculator
• Flat pattern calculator

FAQ

Which formula should I use for a print dimensioned to outside flanges?

Planned answer: use bend deduction or convert carefully from outside setback, then verify with the shop's actual K-factor and radius.