How Close Can a Hole Be to a Bend Line Before It Distorts?

Keep a hole edge at least two to three times material thickness away from the bend line, more for thicker stock or larger holes. Closer, and the bending force pulls the hole out of round or shifts its position once the part is formed.

What's actually happening at the bend

A press brake forms a bend by stretching the outer fiber of the material and compressing the inner fiber. That deformation isn't confined to a mathematically sharp line. It spreads out over a zone on either side of the bend, roughly proportional to material thickness and bend radius. Any feature inside that zone gets dragged along with the material as it moves. A hole that straddles or sits right at the edge of that deformation zone ovals, because the material on one side stretches or compresses more than the material on the other.

Even a hole fully outside the visible bend radius but still close can shift slightly in position. The flat pattern's math assumes the bend happens along a clean line, and real material doesn't quite cooperate. Tighter bend radius relative to thickness makes this worse, since the deformation concentrates more.

Where the rule of thumb breaks down

Thicker material needs more clearance, not less. A bend in 6 mm stock disturbs a wider zone than the same bend in 1 mm stock, even though the ratio-based rule of thumb scales down. Slotted or non-round holes near a bend are more sensitive than round ones. They don't distribute local stress evenly and distort more visibly, or crack at a corner.

Bend relief cuts change the calculation too. A relief slot isolates the hole from the bend, and the distance rule loosens up. Without relief, the two features stay mechanically connected, so the conservative spacing applies.

What to actually do

Push holes that need to stay round and accurately located away from bend lines whenever the design allows it. If a hole has to sit close to a bend for functional reasons, call out the position tolerance you actually need on the drawing. Don't assume the flat pattern software's placement survives forming exactly as modeled.

DigiForge's sheet metal process holds ±0.13 mm on the cut and ±0.5° on the bend angle, but that's for the cut and the bend independently. A hole crowded against a bend line is a geometry problem the tolerance stack doesn't fix on its own. If you're not sure a hole placement is safe, move it back from the bend and re-check function before sending the DXF.