Fold a sheet of metal on a press brake and the corner comes out rounded. It has to: the metal on the outside of the bend is stretched and the metal on the inside is compressed, and the sheet takes the smallest radius it can without cracking. On a bracket nobody cares. On a lift portal in mirror stainless, or a column wrap under a lobby downlight, the eye reads the soft corner at once and the panel looks like folded sheet instead of solid metal.
V-grooving removes most of the material along the fold line before the fold. A V-shaped groove is cut into the back of the sheet, leaving a thin skin on the face side. When the sheet is folded, the two walls of the groove close on each other and the skin becomes the corner — sharp, with almost no radius, because there is almost no material left to bend. The decorative face is never touched: the tool works from behind, and the front arrives on site exactly as it left the polishing line or the PVD chamber.
Where the process is used
- Column cladding and wraps, folded to fit the structure on site.
- Wall panels and cassettes with folded returns, where a rounded edge would read as a mistake.
- Door and frame details: architraves, reveals and frame profiles in finished sheet.
- Furniture and joinery metalwork: reception counters, display plinths, cladding to joinery.
What it asks of the sheet
Because the corner is a thin skin, it is a thin skin. A V-grooved corner is not as strong as a full-thickness bend and is not meant to be: it is a cladding detail, carried by the substrate or the frame behind it, not a structural member. The groove depth is set against the sheet thickness so that enough skin remains to fold without tearing, and not so much that the corner rounds. Grade matters too. The austenitic stainless grades fold well because they are ductile, and the process suits mirror, hairline and PVD-finished sheet precisely because the face is untouched.
Panels that need the back closed, welded or filled are handled after folding on the same order, and the folded piece is film-protected before it leaves.
V-grooving or bending?
- Bending, for anything structural, anything hidden, and anything where a radius is acceptable. Faster and stronger.
- V-grooving, for the corner the client will look at: decorative cladding in a finished sheet where the edge is the detail.
Most decorative jobs use both. The returns nobody sees are bent; the visible arris is grooved.