Sheet metal fabrication
How do I calculate bend allowance and the K-factor?
Answer
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 same bend from different sides.
Sources
- Bend Allowance Formula: BA, BD and K-FactorQ: 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...
- Sheet Metal Bend Allowance & Springback Guide | BalfordThe 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...
- Bend Allowance Formula: BA, BD and K-FactorTerm What it is Where it is used Bend allowance (BA) Length of the neutral axis through the bend arc Added to inside leg lengths, or removed from outside dimensions Bend deduction (BD) BA minus the setback, doubled Subtracted from the sum of the outside leg lengths Outside setback (OSSB) Distance fr...
- Custom Sheet Metal Bending Services | BalfordDo 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...
- K-Factor in Sheet Metal: What It Is and How To Set ItFor the next calculation, review the sheet metal bend allowance and springback guide , the springback calculator and sheet metal processing . Frequently asked questions What is a typical K-factor for sheet metal? Between 0.33 and 0.50. A tight bend in a work-hardening material sits near 0.33, a gene...
- Metal Fabrication & Stamping Blog | BalfordMetal 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...
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
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Send the engineering drawing (STEP or PDF) with the material grade, thickness and annual volume. Balford engineers then check it against the process window - draw ratio, wall thickness, tolerances, blank and tooling route - and come back with what is feasible and what is not. An answer on this page cannot replace that review.
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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.