Guides / Pro
Sheet metal bending
PRODeveloped length and bend deduction for the press brake, tuned to your machine.
What it is for
How long do you cut the strip so the legs come out right after bending? The app works out the developed length from the outside dimensions, thickness, inside radius and angle, per DIN 6935 or with the K-factor of your own machine.
Where to find it
Calculator → Sheet metal bending.
Step by step
Pick material and sheet
Under Material & sheet: the material and the thickness.
Give radius and angle
The inside radius you really work with, and the bend angle. 90° is a square bend, measured from flat.
Give the legs
Flange A and flange B, measured on the outside to the peak of the bend, the way you lay the tape on it.
Read the developed length
Large at the top: that is how long you cut the sheet. Below it the bend deduction and the K-factor.
Tune it to your machine
With "Do a test bend" you bend one strip exactly 90° and measure the legs. The app works back to the real K-factor of your machine and die and keeps it in "My bend table".
Worked example: A small angle in 2 mm steel
Sheet 2 mm, inside radius 2 mm, 90°, legs 50 and 30 mm outside. K-factor per DIN 6935.
| What | Result |
|---|---|
| K-factor | 0.325 |
| Bend deduction | 3.8 mm |
| Developed length | 76.2 mm |
How the app calculates
- K = (0.65 + 0.5 × log(R/T)) / 2 = 0.325 when R = T.
- Bend allowance = π/2 × (2 + 0.325 × 2) = 4.16 mm. Outside setback = tan 45° × (2 + 2) = 4 mm.
- Bend deduction = 2 × 4 − 4.16 = 3.84 mm. Developed length = 50 + 30 − 3.84 = 76.2 mm.
Tips for the best result
- A test bend on your own press brake is more accurate than any table. Measure the strip as precisely as you can first.
- DIN 6935 is a steel standard. For stainless and aluminium the formula is an approximation: do a test bend there for sure.
- If the inside radius is smaller than the sheet thickness, the app warns about cracking on the outside.
- A flange shorter than about 0.7 × the V opening does not bear on the die. Pick a narrower V or a longer flange.
Questions
Does it work above 90°?
Measuring to the peak only exists up to 90°. Above that the app gives no bend deduction on outside dimensions.