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Calcimator

Bend Allowance Calculator

Calculate flat pattern bend allowance and deduction from material thickness, bend angle, inside radius, and K-factor.

Inputs

mm
°
mm

Results

Bend Allowance

3.92 mm

Bend Deduction3.08 mm
Outside Setback (OSSB)3.5 mm
Neutral Axis Radius2.5 mm
Outside Radius3.5 mm
Minimum Flange Length6 mm
Arc Length (Neutral Axis)3.92 mm
How to Use This Calculator
  1. Enter material thickness (in) and inside bend radius (in).
  2. Set the bend angle (degrees) and K-factor -- mild steel: 0.33-0.42, aluminum: 0.40-0.50.
  3. Review bend allowance (in) -- the arc length consumed in the bend zone.
  4. Subtract bend allowance from the flat blank to get flat pattern dimensions for each flange.
  5. Verify K-factor against material supplier data or run a test bend to calibrate for your specific stock.

How the result changes with Bend Angle

Bend AngleBend Allowance
190.83 mm
642.79 mm
1175.1 mm
1627.05 mm

What each input means

Material Thickness
Sheet metal thickness (gauge converted to mm).
Bend Angle
Included bend angle in degrees (90° for a right-angle bend).
Inside Bend Radius
Inside radius of the bend (typically 1-2× material thickness).
K-Factor
Neutral axis position (0.33 for air bending mild steel, 0.40-0.50 for bottoming).

What each result means

Bend Allowance
Length to add to flat pattern for the bend.
Bend Deduction
Length to subtract from total flange dimensions.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Material Thickness = 1.5, Bend Angle = 90, Inside Bend Radius = 2, K-Factor = 0.33 = 4 input(s) provided
  2. Calculate Bend Allowance
    Bend Allowance
    3.919 = 3.919
  3. Calculate Bend Deduction
    Bend Deduction
    3.081 = 3.081
  4. Calculate Outside Setback
    Outside Setback
    3.5 = 3.5

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