V-grooving vs conventional bending

In air bending and bottoming alike, the sheet is pushed into a die by a punch and takes up a radius governed by the tooling, the material and the thickness. As a rule of thumb the internal radius is of the order of the sheet thickness, and the external corner is larger again. Nothing about the press brake can make that corner sharp — it is a property of wrapping metal around a tool.

By removing material before the fold, grooving reduces how much metal has to bend at all. The web left at the bottom of the groove is thin, so it closes far more tightly, and the external corner follows.

Conventional bending: fewer operations, full section thickness maintained through the corner, structurally stronger, cheaper, visible external radius. V-grooved bending: extra machining operation, reduced section at the bend, sharp external corner, flatter visible face, higher cost.

The question is not which is better but where the corner sits. A specifier who grooves everything is paying for corners nobody will see; one who grooves nothing gets soft-edged profiles in the positions that matter most. MCS reviews the section and says which bends warrant it.