DIN 6935 Sheet Metal K-Factor, Bend Deduction (BD) & Air-Bending V-Die Reference Chart
Parametric Formulas & Dimensional Allowances
True arc length along the neutral axis through a 90-degree press-brake bend.
Amount subtracted from the sum of two outside flange dimensions to obtain the true flat blank length.
Prevents adjacent 90-degree flanges from colliding or tearing at the corner bend intersection.
Standard Material & Tooling Tolerance Table
| Sheet Metal Gauge / Stock | Thickness (T) | Recommended V-Die (8×T) | Inside Air-Bend Radius (R_i) | Air-Bend K-Factor | 90° Bend Deduction (BD) |
|---|---|---|---|---|---|
| 20 ga CRS / Galvanized Steel | 0.95 – 1.00 mm | 8 mm V-Die | 1.00 mm | 0.42 | 1.77 mm |
| 18 ga Mild / Galvanized Steel | 1.21 mm | 10 mm V-Die | 1.21 mm | 0.42 | 2.15 mm |
| 16 ga CRS Mild Steel | 1.52 mm | 12 mm V-Die | 1.52 mm | 0.42 | 2.70 mm |
| 14 ga Structural Steel | 1.90 – 2.00 mm | 16 mm V-Die | 2.00 mm | 0.42 | 3.55 mm |
| 1.5mm 304 Stainless Steel | 1.50 mm | 12 mm V-Die | 1.50 mm | 0.44 | 2.62 mm |
| 2.0mm 5052-H32 Aluminum | 2.00 mm | 16 mm V-Die | 2.00 mm | 0.40 | 3.61 mm |
| 3.0mm 5052-H32 Aluminum | 3.00 mm | 24 mm V-Die | 3.00 mm | 0.40 | 5.42 mm |
Generate Custom 1:1 .DXF, .SVG & .PDF Files Using This Standard
Sheet Metal 4-Flange Pan
Generate 1:1 unfolded sheet metal 4-flange pans, chassis trays, and electrical enclosures in .DXF, .SVG, and .PDF with automatic DIN 6935 K-Factor bend deduction and corner relief notches.
Sheet Metal U-Channel Bracket
Generate 1:1 unfolded sheet metal U-channels, clevis brackets, and 2-flange mounting brackets in .DXF, .SVG, and .PDF with DIN 6935 K-Factor bend deduction and bolt holes.
HVAC Duct Transition / Reducer
Generate 1:1 unfolded HVAC sheet metal duct transitions, concentric reducers, and pyramid hopper flat patterns in .DXF, .SVG, and .PDF with true slant height triangulation.
90° Corner Gusset Plate
Generate 1:1 90-degree structural corner gusset plates and T-slot aluminum extrusion brackets in .DXF, .SVG, and .PDF with weld-relief corner notch and ISO bolt holes.
Ready-to-Cut Product Presets (Sheet Metal & HVAC)
220 mm x 140 mm Base with 40 mm Vertical 90-Degree Press-Brake Flanges
120 mm Web Width × 80 mm Depth × 50 mm Side Flange Legs (Formed 90° U-Bracket)
200 × 200 mm (8") Bottom Inlet Reducing Concentrically to 150 × 150 mm (6") Top Outlet
EIA-310 19-Inch Rack Inner Chassis Width (430 mm) × 200 mm Depth × 44.0 mm (1U) Height
Fits Standard 40 × 40 mm T-Slot & V-Slot Aluminum Extrusion Framing (120 × 120 mm Legs)
Braces 50 × 50 mm (2" × 2") and 75 × 75 mm (3" × 3") Square RHS Steel Tube Frames
Shop-Floor Troubleshooting & Engineering FAQs
Why does CadFold use K = 0.42 as the standard sheet metal K-Factor?
For standard press-brake air bending where the inside bend radius approximately equals material thickness (R_inside ≈ T) over an 8×T V-die opening, K = 0.42 is the empirically verified industry standard across mild steel and 5052 aluminum.
What happens if I omit corner relief cutouts on a 4-flange sheet metal pan?
Where two perpendicular bend lines intersect at a box corner, the metal is forced to deform in two planes simultaneously, causing ugly corner bulging, cracked paint/galvanizing, and inaccurate flange angles.
How are HVAC square-to-round and trapezoidal duct transitions unfolded?
Because tapered hopper and duct reducer walls slope inward, our HVAC Transition Generator calculates the true 3D slant height S = sqrt(H² + ((L - W)/2)²) rather than using vertical height H.
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