V-Die Opening (Air Bending)
We consistently use:
V = 8 x material thickness (t)
Examples:
- t = 2 mm -> V = 16 mm
- t = 5 mm -> V = 40 mm
Inside Bend Radius (Ri)
With V = 8 x t, the resulting inside radius is approximately:
Ri ≈ 1.0 x t (for steel)
Typical variations:
- Mild steel: ~1.0 x t
- Stainless steel: ~1.0-1.2 x t
- Aluminum: ~0.8-1.2 x t
Bend Allowance & K-Factor
BA = A x (π / 180) x (Ri + K x t)
Where:
- A = bend angle (degrees)
- Ri = inside bend radius
- t = material thickness
- K = K-factor
- Typical K-factor: K ≈ 0.30-0.40 (commonly ~0.33 for mild steel)
Minimum Flange Length
Minimum flange length ≈ 4 x t
Tolerances & Influencing Factors
Typical tolerances:
- Material type and yield strength
- Rolling direction (grain)
- Tooling wear and press brake setup
- Batch variations in material
- Angle: ±0.5° to ±1°
- Linear: ±0.2-0.5 mm
Design Recommendations
- Keep holes/cutouts ≥ 2-3 x t from bend lines
- Avoid sharp internal corners
- Define bend direction clearly
- Provide STEP + DXF when possible
Summary
- Air bending with V = 8 x t
- Inside radius ≈ material thickness
- K-factor ~0.33 (guideline)
Air-bending reference table
Use these steel planning values to check a design before upload. They are based on a V-opening of 8 × material thickness; final tooling is confirmed against the material, geometry and required angle.
| Thickness (t) | V-opening (8 × t) | Inside radius (≈ 1 × t) | Minimum flange (≈ 4 × t) | Hole from bend line (2–3 × t) |
|---|---|---|---|---|
| 1.0 | 8 | ≈ 1.0 | ≈ 4 | 2–3 |
| 1.5 | 12 | ≈ 1.5 | ≈ 6 | 3–4.5 |
| 2.0 | 16 | ≈ 2.0 | ≈ 8 | 4–6 |
| 3.0 | 24 | ≈ 3.0 | ≈ 12 | 6–9 |
| 4.0 | 32 | ≈ 4.0 | ≈ 16 | 8–12 |
| 5.0 | 40 | ≈ 5.0 | ≈ 20 | 10–15 |
| 6.0 | 48 | ≈ 6.0 | ≈ 24 | 12–18 |
Reference only: stainless steel and aluminium can require different radii, bend allowances and springback compensation. Short flanges, features near a bend, return bends and tight profiles are reviewed against the actual tooling.
This ensures consistent, repeatable, production-ready results.
For further clarifications please email us at post@metalldel.no