Bent bracket

The surface is developable and the flat pattern is solved in closed form. Cut the part to the drawing and it fits — the whole uncertainty sits in the K-factor, which belongs to the material and the machine, not to the geometry.

Dimensions are entered as: Outside dimensions. The flat pattern itself is always computed on the neutral fibre — at Ø800 in 3 mm sheet the difference between the inside and the outside dimension is 18.8 mm of developed width, and then the seam does not meet.

En 90°-bøjning af vinkeljern (L-profil): to lige ben med L-tværsnit — en flange i hver retning og samme godstykkelse — der mødes i et fælles hjørne med ret vinkel mellem benene.

Hjørner i rammer, beslag og afstivninger hvor et vinkeljern skal dreje 90°. Bruges i stålkonstruktion, maskinrammer og bæringer hvor L-profilets stivhed udnyttes i hjørnet.

Smed, metalsmed og industritekniker — hjørner i rammer, beslag og afstivninger, hvor et vinkeljern skal dreje 90°.

Konstruktionsstål S235/S355 vinkeljern. Gering skæres og svejses; ved koldbøjning af flad plade til L: R ≥ t.

Source: Bærende stål: EN 1090 (smede-artikel i src/lib/skoler/indhold/data.ts + kilder.ts). Materialer/tykkelser: src/lib/kasse/materialer.ts (DIN 6935 for stål; massefylder og handelstykkelser; springback). Fremstillingsfælder: docs/PLAN-UDFOLDNINGSBIBLIOTEK.md §9.2/§4.

Flange — Flange width

Bredden af hver af L-profilets to flanger i mm. Den udfoldede strimmel bliver 2 × flange bred, med folden i midten ved x = flange.

Godstykkelse — Goods thickness

Profilets pladetykkelse i mm (clampes altid til mindre end flangen, så tværsnittet forbliver et ægte L).

Benlængde — Leg length

Længden af hvert ben i mm — svarer til strimlens højde (ekstruderings-dybden langs profilet).

Step by step with compass and square — in cardboard first, in sheet metal after.

1. 01Tegn pr. ben et rektangel: bredde = 2 × flange, højde = benlængde.
2. 02Sæt en fals-/foldlinje på langs i midten ved x = flange — det er L'ets indvendige hjørne mellem de to flanger.
3. 03Gentag så du har to ens strimler (Ben A og Ben B), med lidt luft imellem.
4. 04Skær strimlerne ud langs yderkanterne og fals langs midterlinjen.
5. 05Buk hver fals til 90°, så hver strimmel bliver et L-profil-ben.
6. 06Stil de to ben vinkelret på hinanden og saml dem i det fælles hjørne.

Bukketillæg ved den indvendige radius er ikke fratrukket i målene — mål efter midterfiber ved præcision. Vælg en bukkeradius der passer til godstykkelsen, så flangen ikke revner i folden.

• ·Er delen bærende (indgår i et byggeri), er den en byggevare omfattet af EN 1090 — CE-mærkning, udførelsesklasse (EXC) og svejsekoordinering. En illustration erstatter ikke dokumentationen.
• ·Stål fjedrer 1–3° tilbage — overbøj efter prøvebuk; regn udfoldningen med den ønskede vinkel.
• ·Denne figur er en illustration uden DXF-udfoldning (skæres ikke direkte).

The words and formulas the trade uses for a flat pattern. The symbols are the same throughout Discebo: α is the bend angle in degrees, R the inside bend radius, t the sheet thickness and K the K-factor — all in millimetres.

Flat pattern (development)

The part's surface laid out flat as one continuous cutting outline — the way the sheet looks BEFORE it is bent or rolled. Only a developable surface can be unfolded exactly; a doubly curved surface cannot be laid flat without stretching the material.

Flat length

The flat length the part must be cut to so the dimensions come out right once it is bent. It is either the sum of the outside dimensions minus the bend deductions, or the sum of the flat legs plus the bend allowances — both routes must give the same number.L = Σ(udvendige mål) − Σ(BD) = Σ(flade ben) + Σ(BA)

Bend allowance

The length of material that sits in the bend itself, measured along the neutral fibre. The bend allowance is always positive and is added to the flat legs.BA = (π/180) · α · (R + K · t)

Bend deduction

The amount subtracted from the sum of the outside dimensions, because the two outside dimensions between them count the corner twice. Here the bend deduction is taken as POSITIVE and subtracted; DIN 6935 writes the same quantity as the compensation value v with the opposite sign.BD = 2 · OSSB − BA

Outside setback

The distance from the theoretical outside corner point in to where the bend starts. Above 90°, tan(α/2) is clamped to at most 1 per DIN 6935, so the number does not explode towards 180°.OSSB = tan(α/2) · (R + t)

Compensation value v to DIN 6935

The standard's own way of writing the same corner loss: the flat length is a + b + v, where v is negative. Our bend deduction is therefore the same quantity with the opposite sign — never flip one without the other.L = a + b + v ⇒ v = −BD

K-factor

Where the neutral fibre sits in the sheet, given as a fraction of the sheet thickness. DIN 6935 writes the correction factor k, which applies to the neutral line in the form (R + t·k/2); the American CAD convention writes (R + K·t), so K = k/2.k = 0,65 + 0,5 · log₁₀(R/t), k ≤ 1,0 ⇒ K = k/2

Neutral fibre

The layer in the sheet that is neither stretched nor compressed when the part is bent. The flat pattern is always computed on the neutral fibre — which is why it matters whether the drawing's dimensions are inside or outside.

Bend angle

The angle the material is turned through, not the angle between the legs. The bend angle is 180° minus the included angle, so a square corner is 90° and a seam fold is 180°.α = 180° − åbningsvinklen

Inside bend radius

The radius on the inside of the bend. It is set by the tooling and the material, not by the drawing — too small a radius cracks the part in the outer fibre.

Sheet thickness

The thickness of the material. It enters every single bend allowance, so sheet delivered 0.2 mm thicker than ordered shifts the flat length at every bend.

Fold line

The line on the flat pattern where the part is to be bent. It is drawn but never cut through — in a laser file it therefore sits on its own layer.

Test bend

A strip of known raw length, bent in the material and the tooling that production will use. Measure the two outside legs afterwards and the bend deduction and K-factor can be worked back. The machine's own measured bend table beats any table.BD_målt = (A + B) − L₀

DIN 6935 covers only cold bending of flat products in structural steel. Stainless, aluminium, copper, brass and titanium zinc are not included — there the formulas are an extrapolation, and a test bend in the actual material settles it.

38 fields. The starting values belong to the figure itself — they live in one place in the code, so the tool, the share link and the smoke test can never disagree about what «default» means.

A preset sets every dimension at once. The name is often the word the part goes by in the workshop — the library's search knows them all.

Read them before the part is cut. They are here because they cannot be calculated away — not as legal text, but as craft.

• The figure draws GEOMETRY. It does not size: load capacity, deflection, the bolts' capacity and the bracket's anchoring have not been calculated. If the bracket is to carry load, the calculation belongs under EN 1993-1-1/-1-8 (steel structures) or the relevant product standard.
• Lifting gear (eye bolts, lifting brackets, slings, hooks) is CERTIFIED equipment with requirements for WLL marking, traceability and testing in accordance with the Machinery Directive 2006/42/EC. A bracket from this figure must not be used for lifting.
• Load-bearing scaffolding components (couplers, brackets, frames) are covered by EN 12810/12811 and must be type-tested — they must not be manufactured according to this figure.
• The K-factor is a qualified SUGGESTION. DIN 6935 covers only structural steel; for stainless steel, aluminium, copper, brass and titanium zinc the formula is an extrapolation. The workshop's own trial bend on YOUR tool and YOUR sheet always takes precedence — enter it under ‘K-factor → Trial bend’.
• Springback has not been allowed for. The development corresponds to the DESIRED angle; the over-bending is the machine's and the operator's responsibility.
• The bend sequence is a suggestion derived from one stated rule (bend from the ends inward, lowest first). The figures that decide the matter — upstanding height and reach per step — are given in the table and must be checked against your own punch, die and back gauge.