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Minimum flange length
A flange that's too short drops into the die's V-opening instead of resting on it. Calculate below the shortest straight leg still achievable after a bend.
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The rule of thumb
The flange needs to be wide enough to rest on the die's shoulders instead of dropping into the V-opening. A common rule of thumb:
minimum flange length = half the V-die width + inside bend radius
This depends mostly on the die, not on thickness by itself — for a given V-die, the minimum flange barely changes if you only change the thickness. Pick a narrower V-die (or a smaller inside radius) if the flange really needs to be shorter.
Distortion zone
Even when the flange is formally long enough, the material right next to the bend line stays somewhat distorted by the bending itself — the same rule of thumb as the hole distance to bend line calculator: radius + 2.5 × thickness. Plan a hole, slot or sharp edge just outside that zone.
This remains a rule of thumb for a first estimate — the actually achievable flange length also depends on the specific die and press. For a borderline case, send your drawing and we'll check it.
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