V-dies
V-die opening, groove angle and shoulder radius; bending-mode differences; and the tradeoffs among flange support, radius, load and mounting.
Tags: tooling, sheet-metal, press-brakes, bending
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Under WILA's approximate steel air-bending guidance for sheet up to about 3 mm, a 2.0 mm sheet gives a 12–16 mm opening at 6–8 times thickness. The guideline requires the flange to exceed half the opening, so exactly 8 mm fails that comparison for V16. Check actual contact geometry, material, force and required radius for the setup. WILA, opening and support guidance.
A V-die supports the sheet over an angled groove, which can allow overbending to compensate for springback. SSAB, Die
Three geometric quantities
| Quantity | Meaning | Distinction |
|---|---|---|
| V-opening | Nominal width across the groove | A length, not an angle |
| Included angle | Angle between the groove faces | Does not alone specify the finished sheet angle |
| Shoulder radius | Rounded transition where sheet bears on the die | Different from the punch-tip and finished inside radii |
WILA measures opening between virtual bearing-surface/groove-face intersections and notes differing manufacturer conventions. Opening affects the naturally formed inside radius; equal nominal widths do not establish identical drawings. WILA, V-opening size
Shoulder geometry shifts the contact as the sheet rotates. Verify groove depth, outside width, working height and tang separately.
Air bending, bottoming and coining
WILA's air-bending description uses contact at the punch and two die shoulders, with the angle controlled by punch penetration. Its bottoming description instead encloses the sheet between matching tools. The same nominal V-opening does not turn these into equivalent processes. WILA, Air bending; WILA, Bottom bending
AMADA's technical guide distinguishes partial bending, where the sheet does not reach the die bottom, from bottoming, with sheet-to-die contact. It describes coining as punch penetration into the workpiece and assigns it substantially greater force. This terminology matters: the guide groups bottoming and partial bending under an “Air Bend” heading, so the specific contact condition is clearer than relying on that heading alone. AMADA, Bending Type & Die V Selection
Engineering interpretation: a die's angle must accommodate the loaded geometry and springback strategy. A 90° final bend does not necessarily require a 90° groove, and an air-bending force estimate does not qualify bottoming or coining. Punch, die, mounting and machine capacities all remain constraints.
Opening rules depend on material and method
WILA's approximate steel air-bending rule is 6–8 times thickness, up to approximately 3 mm sheet. Its support condition requires flange length greater than half the opening. Neither guarantees crack-free bending. WILA, opening and support guidance
The rule does not transfer automatically to stainless steel, aluminum tempers or high-strength plate. SSAB's force guidance identifies bend length, plate thickness, die width, tensile strength, changing moment arm and friction as relevant inputs. Its recommendations are scoped to SSAB products. Material identity and the forming conditions therefore matter beyond thickness alone. SSAB, press force for press-brake operation
A smaller opening can support a shorter flange, but it also changes contact, radius and required force. WILA warns that changing the opening changes the radius and consequently the flat pattern. A shorter-flange solution is therefore a geometry and load tradeoff, not just a different tool number. WILA, short-flange tradeoffs
Load rating and mounting are separate specifications
WILA's catalog page 74 lists OZU-401 through OZU-404 bottom-tool variants, with NS VI shoulder-load adaptation and V-Lock. The entries include full and sectioned lengths and a printed maximum line-load rating of 60 t/m. The mounting and rating belong to those entries; “V-die” alone supplies neither. WILA catalog, New Standard Pro bottom tools, page 74
As engineering synthesis, a line-load rating describes permissible force per loaded length under its product conditions. It is not the press's total force, nor proof that every short segment or off-center setup is acceptable. Holder support, clamping, tool orientation, working height and the load path into the bed remain part of compatibility. A die with a suitable groove can still have the wrong mounting interface.
Worked example: thickness ratio and flange support
Original arithmetic: assume 2.0 mm steel within the cited rule's scope:
6 × thickness = 6 × 2.0 = 12.0 mm
8 × thickness = 8 × 2.0 = 16.0 mm
Half of a 16 mm opening = 8.0 mm
The range is 12–16 mm. Exactly 8 mm does not exceed half V16. This arithmetic does not qualify a material lot or predict force, radius or the actual minimum flange.
Coverage and source dates
No technical publication date was established for the cited web pages or WILA catalog page. Copyright years and catalog URL names are not treated as issue dates. Sources were inspected on November 2, 2026.
These references establish geometry and selected manufacturer guidance. They do not establish universal opening ratios, shoulder radii, tonnage, minimum flanges, final radii, springback allowances or tooling interchangeability. Grade, condition, thickness, bend direction, forming mode and the actual tool assembly remain application-specific. Catalog examples do not establish a shop's installed tooling or approved process.