How to Use K-Factor Calculator
The K-Factor Calculator is the heart of any sheet metal flat-pattern routine.
- Pick a unit — mm, cm or inch — and stick with it for all inputs.
- Enter material thickness T — Provide the nominal sheet thickness.
- Enter the neutral axis offset t — Either measure it on a bent sample or use a vendor-recommended value. Alternatively, type a K value directly to override.
- Enter inner radius and bend angle — Add the punch / die geometry and the bend angle in degrees.
- Read the result — The K-Factor Calculator shows the K-Factor, bend allowance (arc length on the neutral axis) and bend deduction.
Formula & Theory — K-Factor Calculator
The K-Factor Calculator uses the standard sheet metal formulas:
K = t / T
BA = (π / 180) × A × (r + K × T)
OSSB = tan(A / 2) × (r + T)
BD = 2 × OSSB - BA| Symbol | Meaning |
|---|---|
| T | Material thickness |
| t | Distance from inside surface to neutral axis |
| K | K-Factor |
| r | Inner bend radius |
| A | Bend angle in degrees |
| BA | Bend allowance (arc length on neutral axis) |
| OSSB | Outside setback |
| BD | Bend deduction |
Why K-Factor matters
The neutral axis (where material is neither stretched nor compressed) shifts inward during bending. K-Factor captures that shift and is the bridge between 3D part geometry and a 2D flat pattern.
Use Cases for K-Factor Calculator
- Flat-pattern generation — Designers use the K-Factor Calculator to derive blank dimensions before sending parts to laser cutting.
- Press brake setup — Operators dial in matching bend angles and lengths based on the calculated bend allowance.
- Tooling selection — Compare different punch / die combinations to find one that fits within material limits.
- CAD / CAM workflows — Feed the K-Factor back into SolidWorks Sheet Metal, Inventor or Fusion 360 to ensure DXFs match what the brake produces.
- Quality control — Reverse-engineer the effective K-Factor from real bent parts and refine future programs.
- Training — Apprentices learn the relationship between thickness, radius and bend allowance through hands-on experimentation.
A correct K-Factor is the difference between parts that fit on assembly and scrap. The K-Factor Calculator keeps that calculation transparent and reproducible.