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Client‑side calculations
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Results
K factor–
Neutral axis distance, t–
Distance from inside surface to neutral axis.
Bend allowance, BA–
Outside setback, OSSB–
Bend deduction, BD–
Formula: BD = 2·OSSB − BA
Angle used–
Results log
| # | Timestamp | Units | T | R | A | K | t | BA | OSSB | BD |
|---|
Example data
| Case | T | R | A (°) | Inputs | Computed K | t | BA | OSSB | BD |
|---|---|---|---|---|---|---|---|---|---|
| 1: From flat+flanges | 1.5 | 1.0 | 90 | F=63, L1=30, L2=30 | 0.6066 | 0.9099 | 3.0000 | 2.5000 | 2.0000 |
| 2: From known BA | 2.0 | 1.5 | 60 | BA=2.2 | 0.3004 | 0.6008 | 2.2000 | 2.0207 | 1.8415 |
| 3: From known K | 1.2 | 1.2 | 90 | K=0.42 | 0.4200 | 0.5040 | 2.6766 | 2.4000 | 2.1234 |
Example values assume consistent units. Flange lengths are measured from tangent lines, not the apex.
Formula used
Neutral axis position
t = K · T
Bend allowance
BA = (π/180) · A · (R + K · T)
Outside setback
OSSB = (R + T) · tan(A/2)
Bend deduction
BD = 2 · OSSB − BA
To estimate K from a trial, determine BA directly or compute BA = Flat − L1 − L2 using flange lengths measured to the tangent points.
How to use this calculator
- Select units and a calculation mode.
- Enter thickness (T), inside radius (R), and bend angle (A).
- If using “From Flat”, provide the flat length and both flange lengths to tangent.
- If using “From BA”, enter your measured bend allowance.
- If using “From K”, enter a known K value to derive BA, BD, and t.
- Press Calculate to view results. Use Add to log to record them.
- Export your log as CSV or PDF for quality records.
Works for common air‑bending layouts. Keep angles within reasonable forming limits.
Reference data for K factor workflows
1) Typical K factor ranges (indicative)
| Material | Process | Typical K range | Notes |
|---|---|---|---|
| Mild steel (CRS) | Air bending | 0.35 – 0.45 | Standard tooling, moderate radius. |
| Aluminum 5052‑H32 | Air bending | 0.38 – 0.50 | Temper and radius affect neutral axis. |
| Stainless 304 | Air bending | 0.40 – 0.50 | Higher springback; verify on trials. |
| Various | Bottoming | 0.25 – 0.35 | Tighter radius, neutral axis closer inside. |
| Various | Coining | 0.45 – 0.50 | Plastic through‑thickness; mid‑thickness neutral axis. |
2) 90° bend allowance quick table (T=1.5 mm, K=0.42)
| Inside radius | R (mm) | BA (mm) | Outside setback, OSSB (mm) | Bend deduction, BD (mm) |
|---|---|---|---|---|
| 0.5×T | 0.7500 | 2.1677 | 2.2500 | 2.3323 |
| 1.0×T | 1.5000 | 3.3458 | 3.0000 | 2.6542 |
| 2.0×T | 3.0000 | 5.7020 | 4.5000 | 3.2980 |
3) Minimum inside radius guidelines (air bending)
| Material | Nominal min R | Comment |
|---|---|---|
| Mild steel | ≈ 1.0×T | Common baseline for general fabrication. |
| Aluminum | ≈ 1.0×T | Softer alloys can tolerate smaller radii. |
| Stainless | ≈ 1.0–1.5×T | Harder to form; avoid cracking. |
| High‑strength steels | ≥ 1.5×T | Check supplier recommendations. |
Values are indicative; verify with shop trials, tooling charts, and material data.