What K-factor should I start with?

Q: What is bend allowance in sheet-metal fabrication?

Bend allowance is the arc length of the neutral axis through the bend region. It is commonly computed as BA = θ(rad) × (R + K × T), where θ is bend angle, R is inside radius, T is thickness, and K locates the neutral axis.

Q: Why can finished parts still be off after using bend allowance?

Real parts vary with die opening, punch radius, grain direction, springback, and material lot. Production work usually applies shop-specific bend deduction tables from measured test bends rather than pure theoretical values.

Question

What K-factor should I start with?

Accepted Answer

A common starting range is 0.30 to 0.50 depending on material and tooling, with many mild-steel air-bend setups near 0.42 to 0.45. Use this tool for first-pass values, then calibrate against your brake and bend-test coupons.

What K-factor should I start with?

Answers