Why Features Near Bends Need Review
A hole or slot close to a bend line changes shape when the material is formed. There is no single safe distance, which is why the review looks at the part.
Almost every bracket drawing has one feature placed close to a bend line. It is the most common issue that turns up in review, and it is usually invisible until the first part comes off the brake.
What happens to the material
Forming stretches the outside of the bend and compresses the inside. A hole, slot or notch inside that zone is pulled out of shape, and the closer it sits to the bend line the more it moves. A hole that reads as round on the flat drawing comes back slightly oval, or a notch that was square opens up.
The distortion is not random, but it is not a single number either. It depends on the material, the thickness, the inside radius, the die opening, the size of the feature and how much of it sits inside the affected zone. That is why no chart answers the question on its own, and why a fabricator who quotes a universal minimum distance is guessing.
What the review looks at
- Distance from the bend line to the edge of the feature, measured on the flat.
- The type of feature. A round hole behaves differently from a long slot running across the bend.
- Inside radius and material thickness, which set how much of the surrounding material moves.
- Whether the feature has to stay true after forming, or only needs to exist.
- Whether the feature could be cut after forming, or moved a short distance without affecting the assembly.
On the press brake, ram position and crowning are set by the control, so the bend itself repeats. The variable is the geometry being formed, not the machine.
What the drawing should say
Mark the features whose position or shape matters after forming. A dimension that must be held to fit a mating part is different from a dimension that describes roughly where something sits, and the drawing is the only place that distinction exists.
Where the design intent is not decided on a feature, say so. A review can work with a question. It cannot work with silence followed by a first article that does not fit.
Why this is a conversation, not a rule
KorFab does not set bending tolerances or minimum distances for a customer design. What the shop can do is read the part, say where a feature sits close enough to a bend to be a risk, and agree how to handle it before the blank is cut. That conversation is cheaper than re cutting a run. Planning laser cut parts that need forming covers where this fits in the sequence.