Carter Machinery

CARTER BENDING REFERENCE · METRIC

Bend allowance & flat length

Set your finished dimensions. See the blank length and bend centres.

Flat cutting length—
Bend 1 from left edge—
Bend 2 from left edge—

01 Finished profile

Outside dimensions to the theoretical sharp corners, as marked on the drawing. For angled parts, measure along each flange, not its horizontal or vertical projection.

02 Bend settings

Included angle: 90° is a right angle; 180° would be flat. Enter the finished inside radius, not the punch tip radius.

Bend 1
Bend 2

03 Calculation method

Finished profile

All dimensions in mm

Dashed extensions mark theoretical sharp corners. Numbers identify bends, not the bending order.

Flat blank & bend centres

Datum: left-hand edge

Blank width is illustrative. Bend centres are the midpoints of the developed bend zones; these are not machine backgauge settings.

Calculation details

Bend allowance and deduction per bend in millimetres
BendIncluded angleAllowanceDeduction

Use a test bend in the actual material and tooling to confirm the blank before production. This calculator covers separate, constant-radius bends; it does not check tooling clearance, minimum flange support, bend sequence, self-intersection or springback. Not for hems or overlapping bend zones.

How the calculation works

For each bend, the bend angle θ = 180° − included angle.

Bend allowance = θ × π / 180 × (inside radius + K × thickness). Outside setback = (inside radius + thickness) × tan(θ / 2). Bend deduction = 2 × setback − allowance.

Flat length = sum of outside lengths − sum of bend deductions. Each bend centre lies halfway along its bend allowance in the unfolded blank. All internal calculations use full precision; displayed results round to 0.01 mm.

The material selection labels the calculation only. It does not assume a universal K-factor or deduction. In deduction mode, the deduction must be compatible with the entered geometry within the supported K = 0–0.5 range.