01 — Why it mattersThe right V-die changes everything.

Bending force isn’t a material property. It’s the combination: sheet thickness, V-die opening, bend length, material grade. Change one and the whole equation shifts.

The most common shop-floor mistake we see is picking a narrower V “just to be safe.” The result: the press runs at the limit, the workpiece gets marked, the inner radius is wrong, and by the end of the shift the operator has burned twice the current. The right V — the one in the chart — does the work with half the force.

This calculator uses our real technical chart, the same one inside the PG SRL configurator. No magic formula here: experience translated into numbers.

02 — CalculatorThe force, for your bend.

Set thickness, V-die (we propose the recommended one, but you can override it), bend length, and material. The result in tonnes tells you which press you need.

Note. Tonnage is indicative: angles below 90°, non-standard materials, and accessories (sequenced dies, blocks) shift the result. For a full check, open the configurator or contact us.

03 — The formulaWhat sits underneath the math.

The base formula is simple:

F (tonnes) = tonPerMeter (chosen V) × L (metres) × k (material)

Where:

  • tonPerMeter is the linear-metre tonnage, already tabulated for the right die-thickness pairing. Mild steel R≈400 N/mm² is the reference.
  • L is the bend length in metres. A 2.5 m bend is 2.5.
  • k is the material multiplier: 1.0 mild steel, 1.5 stainless, 0.45 aluminium. Average values: the specific alloy can swing ±15%.

Worked example. Mild steel, 4 mm thick, V32 (recommended), 3 m long: F = 34 × 3 × 1.0 = 102 tonnes. Same job in stainless: F = 34 × 3 × 1.5 = 153 tonnes. Same geometry, same tooling, +50% required force.

04 — V-die chartThe shop-floor tool, in full.

All thicknesses from sheet-metal (0.6 mm) to heavy fabrication (50 mm), with recommended V openings for each thickness, indicative inner radius, and minimum flange. The V marked with ◆ is PG SRL’s recommendation: V/thickness ratio between 6× and 8× for mild steel.

◆ = PG SRL recommended V-die. Minimum flange (B) is the shortest flange the die can grip — shorter bends need special tooling (narrow punches, 88° tools). Inner radius is indicative for air bending on mild steel; for coining, the radius follows the punch geometry.

05 — Limits and disclaimerWhat the calculation doesn’t cover.

The calculator covers the standard shop case: air bend, 90° angle, single material, one bend at a time. Cases that need a case-by-case review:

  • Acute angles (≤60°) — the force multiplier grows non-linearly. A 30° bend on 4 mm steel can demand twice the force of a 90° bend.
  • Coining — material closed between punch and die. Force is 3-10× the air-bend value.
  • Coated sheet (galvanised, pickled, pre-painted) — coatings add 5-10% apparent strength.
  • High-strength steels (S355, S690, Domex) — use specific multipliers: S355 ×1.2, S690 ×1.7.
  • Bends longer than the machine — switch to a tandem configuration or split the geometry.

For non-standard cases the PG SRL configurator applies a fuller evaluation (industry, volume, geometry) and our engineering team closes the quote with the final sizing.

06 — Next stepsYou have the bend. Now the machine.

We close the sizing with you.

You have a tonnage, a length, and a material. The missing piece is the machine: see the full range or jump straight into the 7-step configurator. Or write to us: contact us with two lines about the work you do and we’ll respond within 24 hours.