Press Brake Tonnage

Force per metre = 1.42 × UTS × T² ÷ V, with UTS in MPa and T and V in millimetres, giving kN/m. It comes from treating the sheet as a beam over the die opening; the 1.42 folds in die friction and strain hardening. Total force is that times the bend length. Bottoming and coining are shown as ×3 and ×8 — the usual rough multipliers; the real value depends on the tooling and how deep the punch is driven.

The suggested V is 8 × T under 3 mm, 10 × T to 10 mm, 12 × T above — the workshop rule. In air bending the die, not the punch, sets the inside radius: about 16 % of V for mild steel, more for stainless, less for soft aluminium, which is why each material preset carries a radius factor. The minimum flange is about 0.7 × V so the sheet still bridges both die shoulders at the end of the stroke.

Published charts use different constants (some inch charts imply about 1.6 instead of 1.42) and different assumed strengths, so ±15 % between sources is normal. Material lots vary; a certificate value entered as a custom UTS is more reliable than a preset. Always check the tooling's own rating, not only the machine's. No data is stored; the same four anonymous usage counts as the rest of the site apply.