Sheet metal fabrication

How do I calculate bend allowance and the K-factor?

Sources

1. Bend Allowance Formula: BA, BD and K-Factor
   Q: What is the difference between bend allowance and bend deduction? A: Bend allowance is the neutral-axis length through the bend and is added to inside dimensions. Bend deduction is twice the outside setback minus the bend allowance, and is subtracted from outside dimensions. Both describe the sam...
2. Sheet Metal Bend Allowance & Springback Guide | Balford
   The neutral axis is the region through the sheet thickness that sees minimal longitudinal strain during bending. Its position is typically expressed as a K-factor. That factor isn't a fixed material property—it shifts with material grade, thickness, inside radius, tooling, and the forming method use...
3. Bend Allowance Formula: BA, BD and K-Factor
   What is the difference between bend allowance and bend deduction? Bend allowance is the neutral-axis length through the bend and is added to inside dimensions. Bend deduction is twice the outside setback minus the bend allowance, and is subtracted from outside dimensions. Both describe the same bend...
4. Custom Sheet Metal Bending Services | Balford
   Do you calculate bend allowance? Yes. Flat pattern development uses bend allowance/deduction and K-factor reviewed against the material. Use our bend allowance calculator for a first estimate, and we confirm the development on your drawing. Can you bend parts before or after other processes? Yes. Be...
5. Metal Fabrication & Stamping Blog | Balford
   Metal Bending Sheet Metal Bend Allowance and Springback Guide When designing custom sheet metal parts, you need to account for bend allowance, bend deduction, and the neutral axis to get flat patterns that fold up to the right dimensions. The neutral axis shifts depending on material thickness and b...
6. K-Factor in Sheet Metal: What It Is and How To Set It
   Whether the part will be air bent, bottomed or coined, if that is already decided. The dimensions that must be held: overall outside size, hole-to-bend distance, or the flat blank itself. Any bend that runs across the rolling direction, if the visible grain matters. Key point K-factor is an input to...

What an engineer still needs from you

• material and material condition (grade, temper)
• material thickness, plus the key diameter, height and wall thickness
• tolerances, burr direction and the visual acceptance standard
• annual volume - it decides whether tooling is single-hit, progressive or transfer
• surface finish, and any secondary machining, annealing or plating

This page is an engineering answer, not a quotation and not a dimensional acceptance. It is generated from Balford's published material and held to the verified company fact sheet.