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Bend radius chart

V width, the inside radius it produces and the force needed, by material and by thickness. The formulas are shown under the table: you can check every value rather than take our word for it.

Les trois formules · Mild steel (S235)

V width: V ≈ 8 × t; the workshop rule, in multiples of the thickness
Inside radius: Ri ≈ 0.16 × V; it follows from the V, it is not something you order
Bending force: F ≈ 1.42 × Rm × t² / V; Rm = 400 N/mm² for this material

MaterialBend length (mm)

Thickness	V width	Inside radius	Force per metre	Force over 1,000 mm
1 mm	8 mm	1.28 mm	7 t/m	7.2 t
1.5 mm	12 mm	1.92 mm	11 t/m	10.9 t
2 mm	16 mm	2.56 mm	14 t/m	14.5 t
2.5 mm	20 mm	3.2 mm	18 t/m	18.1 t
3 mm	24 mm	3.84 mm	22 t/m	21.7 t
4 mm	32 mm	5.12 mm	29 t/m	29 t
5 mm	40 mm	6.4 mm	36 t/m	36.2 t
6 mm	48 mm	7.68 mm	43 t/m	43.4 t
8 mm	64 mm	10.24 mm	58 t/m	57.9 t
10 mm	80 mm	12.8 mm	72 t/m	72.4 t

Indicative values, air bending. They depend on your tooling, the condition of your dies and the grain direction of the sheet. Always check your press capacity before starting a run.

The three formulas behind the table

V width

V ≈ 8 × t

The workshop rule. A narrower V gives a tighter radius but needs more force and marks the material more. A wider V does the opposite.

Inside radius produced

Ri ≈ 0.16 × V

In air bending the radius is not set by the punch: it follows from the V width. That is why a customer cannot demand any radius they like without changing tooling.

Bending force

F ≈ 1.42 × Rm × t² / V

In newtons per millimetre, converted here to tonnes per metre. Thickness is squared: going from 2 to 4 mm does not double the force, it quadruples it.

Pour aller plus loin

Bend allowance calculatorThe flat length to cut before bending, from your dimensions and your K-factor.Bending forceWhere the tonnage column formula comes from, and the mistakes it prevents.Minimum bend radiusWhat your material takes, and what happens when you push it.Minimum distance to edgeWhy the V width decides what is bendable, holes included.SpringbackCoining needs three to five times the tonnage in the table above.Metal cutting configuratorFrom the customer's raw enquiry to a part you can price, with your constraints.

See these constraints applied live inside a quote

Your constraints, applied before the quote goes out

Koventor knows your materials, your thicknesses, your Vs and your radii. A part your press cannot bend is refused at entry, not discovered on the shop floor.

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