K-Factor Calculator

Your details

Total sheet thickness before bending.
mm
The radius of the inner surface of the bend (the punch radius for air bending).
mm
The included angle of the bend (not the complementary angle). 90 deg is a right-angle bend.
deg
Lookup uses an industry reference table. Manual lets you enter your own measured K-factor. Back-calculate derives the K-factor from a known bend allowance (e.g. from a test bend).
Air bending lets the punch stop before reaching the die; bottom bending pushes the material to the die surface; coining fully plastically deforms the material.
Soft: annealed aluminum, soft brass or copper. Medium: mild steel, 5000-series aluminum. Hard: stainless steel, spring steel, hard copper.
Optional: length of the first flat leg (measured from the tangent point). Used to calculate the flat blank length.
mm
Optional: length of the second flat leg. Used to calculate the flat blank length.
mm
K-factor (K)Typical range
0.43

Ratio of neutral axis position to material thickness (0 to 0.5)

Neutral axis offset (t)1.29mm
Bend allowance (BA)6.7387mm
Outside setback (OSSB)6mm
Bend deduction (BD)5.2613mm
Flat blank length94.739mm
0.43
Very tight<0.33Soft/tight0.33-0.42Typical0.42-0.48Wide radius0.48-0.5Out of range0.5+

K-factor 0.4300 - typical range

  • The neutral axis sits 43.0% of the way through the 3 mm sheet, at 1.290 mm from the inside surface.
  • Your bend allowance is 6.739 mm: this is the arc length of material consumed by the bend zone and must be included in your flat blank.
  • Bend deduction is 5.261 mm. Subtract this from the sum of your two flange lengths to get the flat blank length.

Next stepVerify your K-factor with a physical test bend before running production: measure the actual flat blank and flange lengths, then use the back-calculate mode to confirm your K.

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