Does a Press Brake's Tonnage Chart Already Account for Die Wear?

No. Published tonnage charts assume a die in as-manufactured condition, with
a sharp shoulder radius and a true V-opening. Once a die has years of bends
on it, the real tonnage needed to hit a given angle drifts from the chart,
and there's no correction factor built into the chart to catch that for you.

What the chart is actually modeling

Tonnage charts are built from material tensile strength, thickness, and the
V-die opening, assuming an ideal punch-to-die relationship: a clean radius on
the punch nose, a die shoulder that hasn't rounded over, and full contact
across the intended bend length. That's a reasonable assumption for new or
lightly used tooling. It stops being accurate once a die shows wear patterns
from repeated use, particularly on a die that's been run hard in one
localized section rather than across its full length.

How wear actually shows up

A worn die shoulder loses its sharp edge and effectively opens up slightly
wider than its stamped rating, which under-predicts the tonnage a chart-based
calculation would call for to hit the same bend angle and inside radius. The
part will spring back more than expected at the tonnage the chart says should
work, and the operator compensates by running more pressure than the
calculation suggests — which is the die telling you its real geometry no
longer matches its nominal rating.

The wear is rarely even across the die's length either. A section that's
absorbed most of a shop's production runs a particular V-opening size while
the rest sits mostly unused, so that section wears faster and behaves
differently from the rest of the same die.

How to actually check it, rather than guess

Run a test bend on scrap stock at the chart tonnage and measure the resulting
inside radius and angle against what the die's nominal rating should
produce. If the bend consistently comes out with more spring or a larger
radius than expected across multiple thicknesses of the same material, the
die's actual behavior has drifted from its rating and the chart number needs
an empirical bump for that specific tool, not a blanket correction across all
dies. Keeping a log of actual tonnage used per die per job, compared against
chart tonnage, is the most reliable way to catch this drift before it turns
into out-of-spec parts, since it's specific to the individual die rather than
something you can predict from a general wear curve.

The practical takeaway

Treat the chart as a starting point for a new or known-good die, not a fixed
truth for tooling that's been in service a while. If a die is producing
results that don't match its rated tonnage, the fix is re-verifying that
specific die against test bends, not assuming the material or the machine
has changed.