What is the formula for minimum flange length?

As a working rule, minimum flange ≈ V/2 + t, where V is the die opening and t the material thickness, because the flange must rest on the die shoulders. Some references quote about 0.7 × V, which gives a similar result for common thicknesses.

Can I bend a 5 mm flange in 2 mm steel?

Only with a small die opening. For 2 mm steel the eight times rule gives a 16 mm opening, whose minimum flange is about 10 mm. A 5 mm flange needs roughly a 6 mm opening, a narrow punch tip and a check on the increased tonnage.

Does the punch tip width matter?

It matters at the very short end. A narrower tip reduces the contact width on the shoulders and can allow a slightly shorter flange, but the tip itself then carries a higher load per millimetre and its rating becomes the limiting factor.

Why did my short flange come out with the wrong angle?

The flange slipped into the die opening because it did not rest on the shoulders. The usual fixes are a narrower opening, a reduced-shoulder die, or a different bend sequence.

Minimum Flange Calculator for Press Brake Bending

What is the minimum flange length in press brake bending?

The minimum flange is about half the die opening plus the material thickness, because the flange has to rest on the die shoulders while the punch pushes the material down. A shorter flange drops into the opening before the bend is complete.

Material thickness t (mm)

V-die opening V (mm)

Punch tip width (mm, optional)

Enter values and press Calculate.

Why does the flange have to rest on the die shoulders?

During air bending the only support for the sheet is the two die shoulders. If the flange is shorter than the distance from the bend line to the shoulder, the sheet slips into the opening, the angle becomes unpredictable and the part is usually scrapped.

The limit is geometric, not a matter of machine power. It is the reason a drawing with a very short return flange often needs a narrower die, a narrower punch tip, or a different bend sequence.

How can I bend a flange shorter than the minimum?

Use a narrower die opening, a punch with a narrower tip, a die with reduced shoulder width, or re-sequence the part so the short flange is formed while there is still material to support it. Each option changes the radius or the force, so re-check both.

Options for short flanges
Method	Effect on minimum flange	Trade-off
Narrower V opening	Lowers it in proportion to V	Higher tonnage, tighter radius
Narrower punch tip	Smaller shoulder contact width	Tip load rating becomes the limit
Reduced-shoulder die	Lowest practical flange	Die is job-specific
Bend sequence change	Avoids the limit entirely	Requires forming simulation

How does the flange length relate to the die opening table?

The die opening fixes both the radius and the minimum flange, so choose the opening from the drawing's flange and radius requirements before you calculate the tonnage.

Rule used throughout this site: minimum flange ≈ V/2 + t, inner radius ≈ 0.16 × V. Some references use 0.7 × V for the flange; the two agree closely for common thicknesses.

Related technical pages

V-die opening selection chart

Opening, inner radius and minimum flange in one table.

V-die opening calculator

Work out the opening from the thickness and material.

Gooseneck punches

Deep profiles that reach over an upstand on a return flange.

Bend allowance calculator

Flat length, bend allowance and bend deduction for the blank.

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Minimum flange calculator