KEVOS® MAKEOS · Fabrication
Sheet Bend Allowance and Deduction
What developed length follows from this bend and K-factor?
Calculate one bend’s neutral-axis allowance and outside-dimension deduction using a supplied K-factor.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Sheet thickness | mm | Measured or drawing thickness. |
| Inside bend radius | mm | Achieved inside radius for the actual tooling and material. |
| Bend angle from flat | ° | Change in direction from flat: a right-angle bend is 90°, not its supplementary angle. |
| K-factor | Neutral-axis distance from the inside surface divided by thickness; calibrate with trials. | |
| Outside flange A | mm | Outside dimension to the theoretical sharp intersection of the outside faces. |
| Outside flange B | mm | Other outside flange dimension to that same virtual sharp. |
Method and formulas
- Bend allowance BA = angle (radians) × (inside radius + K × thickness).
- Outside setback SB = (inside radius + thickness) × tan(angle / 2).
- Bend deduction BD = 2 × SB − BA. Developed length = A + B − BD.
- Example: t = 2, R = 3, K = 0.4 and a 90° bend gives BA = 5.969026 mm, BD = 4.030974 mm; 30/40 mm outside flanges develop to 65.969026 mm.
Limitations
- K is process-specific, not a material constant. Outside-dimension conventions must match this method.
- No bend-force, minimum-radius, springback or manufacturability prediction.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- bend deduction
- flat pattern
- K factor
Who it is for
- Sheet-metal designers
- Fabricators
What you get
- Bend allowance
- Outside setback
- Bend deduction
- Developed length
Interpreting the result
- Cut and measure a trial strip before releasing a production flat pattern.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1346–1352. Topic reference; no source tables or recommended settings are reproduced.
- SOLIDWORKS Design Help: K-Factor — https://help.solidworks.com/2026/english/solidworks/sldworks/c_K_Factor.htm
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