Choosing the V-Die: One Wrong Step, One Ton Off

People often fill in the tonnage calculator, look at the number and think it "looks off". Usually it isn't the formula — it's the wrong V-die.

Bending force is inversely proportional to V-die width. The smaller the V, the higher the force.

Same 2 mm sheet, from the table:

V12 → 220 kN/m
V25 → 110 kN/m

Same sheet, different die, double the force.

Picking V by thickness

's recommended ranges, as a multiple of sheet thickness t:

t = 0 – 3 mm V ≈ 6 × t
t = 3 – 8 mm V ≈ 8 × t
t = 8 – 12 mm V ≈ 10 × t
t ≥ 12 mm V ≈ 12 × t

2 mm sheet → V around 12 mm. 6 mm sheet → V around 48 mm.

Why this matters when you buy a machine

If you calculate force using a V-die that is too wide for the thickness, the tonnage comes out lower than reality — and you may buy a machine short on tonnage.

The other way round, a V that is too narrow sends the force up sharply, damages dies and leaves marks on the sheet surface.

On the shop floor

• Not sure which V: leave it blank and the tool applies the table above.
• Already own a die set: enter the V you actually have — the figure will be closer to reality.
• Bending thick plate with a narrow V: check the die's own load limit first, not just the machine's tonnage.