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V-Die Opening Calculator

Estimate only: actual tonnage and radius depend on material tensile, grain direction, springback, and tooling condition. Verify machine capacity and tooling load limits before operation.

Choose a starting V-die opening from sheet thickness and estimate the resulting air-bend inside radius and minimum flange. Verify with your tooling supplier's chart before cutting.

mild steel16 ga0.0598 in1.519 mm

Interactive calculator

V-Die Opening Calculator

Recommended V opening0.3588 in
Opening factor6T
Estimated inside radius0.0574 in
Estimated minimum flange0.2512 in

Static reference

Common V-die and tonnage combinations

Swipe table horizontally for more columns.

GaugeThicknessRecommended VInside radius estimate48 in bend tonnage
20 ga0.0359 in / 0.912 mm0.2154 in0.0345 in13.76 tons
16 ga0.0598 in / 1.519 mm0.3588 in0.0574 in22.92 tons
12 ga0.1046 in / 2.657 mm0.6276 in0.1004 in40.1 tons
10 ga0.1345 in / 3.416 mm1.076 in0.1722 in38.67 tons

Formula used

What this calculator computes

V = factor × t
V
Recommended V-die opening (in)
factor
6 (t ≤ 1/8"), 8 (1/8" < t ≤ 1/2"), 10 (t > 1/2") (ratio)
t
Material thickness (in)
  • Common shop rule for air bending mild steel and aluminum. Heavier plate, harder alloys, and high-strength steels often shift the factor up.
  • Default thresholds (1/8" and 1/2") are starting breakpoints — your tooling supplier may publish different ones.
IR ≈ 0.16 × V
IR
Estimated produced inside radius (in)
V
V-die opening (in)
  • Widely cited as the 16% rule for air bending. Actual produced radius depends on punch tip radius, material, and springback.
Min flange ≈ 0.7 × V
Min flange
Minimum flange length to clear the die (in)
V
V-die opening (in)
  • Below this length the flange may roll into the die or slip on the shoulders. Some shops use 0.67×V or 0.75×V instead — confirm against the die geometry.

Worked example

One numeric walk-through

Inputs

Thickness t
0.125 in (1/8")

Steps

  1. t ≤ 0.125 → factor = 6.
  2. V = 6 × 0.125 = 0.75 in.
  3. IR ≈ 0.16 × 0.75 = 0.12 in.
  4. Min flange ≈ 0.7 × 0.75 = 0.525 in.

Result

Start with a 0.75 in V opening. Expect ~0.12 in inside radius and need ~0.525 in minimum flange length. Verify with the die supplier's published chart.

Common mistakes

Things to check before trusting the number

Related calculators

Move between connected shop calculations

TonnageV-die openingBend allowanceMinimum bend radiusData sources

FAQ

Specific checks for this calculator

What V-die opening should I start with?

6× thickness for thin sheet (≤ 1/8"), 8× thickness for medium sheet (≤ 1/2"), and 10× thickness for heavy plate are common starting points. Verify with your tooling supplier.

Does a larger V opening reduce tonnage?

Yes — air-bend tonnage scales as t² / V, so a wider V opening reduces force at the cost of a larger inside radius and a longer required minimum flange.