Lid and base joints
For a case that opens, pair the double angle with a mating lid profile (tongue-and-groove or "hybrid" section) so the lid locates and seals on closing.
Panel-joining extrusions
Double Angle Aluminium Extrusions
A double angle extrusion is an aluminium corner profile with two slots set at 90°, so that two panels slide or click into it and form a square, reinforced edge. It is the standard framing member for flight cases, road cases, display cabinets and panel enclosures. Metline supplies double angle profiles in 6063 and 6061 with slots for common panel thicknesses, cut to length and finished as required, worldwide.
- Joint
- 90° panel corner
- Panel sizes
- 1/8 – 3/4 in (3 – 19 mm)
- Alloys
- 6063-T5/T6 · 6061-T6
- Finishes
- Mill, anodised, black, powder
What a double angle extrusion does
Two panels meeting at a right angle are the weakest point of any box. A double angle extrusion wraps that corner in metal: each panel edge sits in its own channel, the outer legs lie flat on the panel faces and are riveted or screwed through, and the rounded or squared nose takes knocks that would otherwise split the board.
The profile is essentially two U channels joined back to back at 90°, sharing a common corner. Because the panels are captured on both faces, the joint resists racking and impact far better than a glued butt joint or a single external angle. Ball corners, brackets and catches are then fitted over the ends where three extrusions meet.
Double angles are made in several variants: with standard or long legs (more leg gives more rivet edge distance and stiffness), with smooth or ribbed outer faces, as a slide-on profile that accepts a range of panel thicknesses, or as a click-on profile with internal barbs that grip a grooved panel edge. Click-on types need the panel thickness held closely; slide-on types are more forgiving but rely on rivets to hold the panel.
The same idea appears in other industries under other names: corner trims for partition and cleanroom panels, glazing corner profiles, and aerospace "double angle" clips that join a frame to a skin. The engineering is the same: two perpendicular surfaces in one extrusion.
Panel thicknesses and supply range
The key dimension is the slot width, which must match the actual panel thickness, not its nominal size. Laminated plywood often measures a few tenths of a millimetre over or under nominal, so measure the panels you will use, or send samples.
| Nominal panel | Metric equivalent | Typical use |
|---|---|---|
| 1/8 in | 3.2 mm | Light display and instrument cases, polycarbonate panels |
| 3/16 in | 4.8 mm | Small cases and inserts |
| 1/4 in | 6.35 mm (often 6 – 7 mm ply) | Light-duty road and carry cases |
| 5/16 in | 7.9 mm | Medium cases |
| 3/8 in | 9.5 mm (often 9 – 10 mm ply) | Standard touring flight cases and rack cases |
| 1/2 in | 12.7 mm (often 12 mm ply) | Heavy-duty cases, large equipment and transport crates |
| 3/4 in | 19 mm | Furniture, partition and heavy panel frames |
Supply range
- Alloys
- 6063, 6060, 6061 and 6082
- Tempers
- T5 or T6 (6063); T6 (6061, 6082)
- Leg length
- Standard and long-leg versions; custom leg lengths to drawing
- Lengths
- Mill lengths around 6 m, or 2, 4, 6, 8, 10, 12 and 25 ft; cut to length on request
- Finish
- Mill, clear or black anodised, gold or bronze anodised, powder coated
- Processing
- Cutting, mitring, hole drilling at rivet pitch, notching and deburring
Alloys, tempers and properties
6063-T5 or T6 is the standard alloy. It extrudes the thin, intricate slot walls and barbs cleanly, takes a uniform anodised colour and is soft enough to rivet without cracking. 6061-T6 or 6082-T6 is used for heavy-duty crates and frames where the extrusion contributes real structural strength, or where a thicker section will be machined.
| Alloy and temper | Standard and size band | Tensile strength, min. | Yield strength (0.2 %), min. | Elongation, min. |
|---|---|---|---|---|
| 6060-T5 | EN 755-2, wall ≤ 5 mm | 160 MPa | 120 MPa | 8 % |
| 6063-T5 | ASTM B221, ≤ 12.5 mm | 150 MPa (22 ksi) | 110 MPa (16 ksi) | 7 – 8 % |
| 6063-T6 | ASTM B221 / EN 755-2 | 205 – 215 MPa (30 ksi) | 170 MPa (25 ksi) | 8 % |
| 6061-T6 / T6511 | ASTM B221 / B308 | 260 MPa (38 ksi) | 240 MPa (35 ksi) | 8 % |
| 6082-T6 | EN 755-2, open profile ≤ 5 mm | 290 MPa | 250 MPa | 8 % |
Specified minimums for extruded profiles; thicker walls fall into different bands. Typical values run 10 – 20 % higher (6061-T6 typically 310 MPa tensile, 276 MPa yield). Design to the minimums and the actual figures on the mill certificate.
| Alloy | Si | Fe | Cu | Mn | Mg | Cr | Zn | Ti |
|---|---|---|---|---|---|---|---|---|
| 6060 | 0.30 – 0.6 | 0.10 – 0.30 | 0.10 | 0.10 | 0.35 – 0.6 | 0.05 | 0.15 | 0.10 |
| 6063 | 0.20 – 0.6 | 0.35 | 0.10 | 0.10 | 0.45 – 0.9 | 0.10 | 0.10 | 0.10 |
| 6061 | 0.40 – 0.8 | 0.7 | 0.15 – 0.40 | 0.15 | 0.8 – 1.2 | 0.04 – 0.35 | 0.25 | 0.15 |
| 6082 | 0.7 – 1.3 | 0.50 | 0.10 | 0.40 – 1.0 | 0.6 – 1.2 | 0.25 | 0.20 | 0.10 |
Single values are maximums. Others 0.05 % each, 0.15 % total; aluminium is the remainder. Limits follow the Aluminum Association registrations and EN 573-3.
Density is about 2.70 g/cm³ for all of these alloys, so the extrusion adds very little weight to a case compared with steel edging, while giving it a rigid, impact-resistant frame.
Designing and assembling with double angles
- Measure panelsMeasure actual panel thickness at several points and choose a slot that gives a snug sliding fit; for click-on profiles, groove the panel edge to the profile drawing.
- Cut and mitreCut extrusions to the panel length; where profiles meet at corners, cut square ends for ball corners or mitre for a seamless frame.
- Fit the panelsSlide or press the panels fully home. A bead of adhesive in the slot reduces rattle and improves water resistance.
- RivetRivet through the outer legs into the panel at an even pitch, keeping holes a safe distance from the leg edge. Aluminium rivets avoid galvanic corrosion; steel rivets give higher pull-out strength.
- Fit hardwareAdd ball corners, brackets, hinges, catches and handles, which are riveted over the extrusion ends.
Long-leg profiles
Choose long legs on heavy or large cases: more leg gives more rivet edge distance and better resistance to panel pull-out.
Honeycomb panels
For lightweight cases, aluminium honeycomb or composite panels can be used in place of ply; check slot size and use inserts at rivet points.
Finishes and appearance
- Mill finish: the economical industrial look; tarnishes to a dull grey in use
- Clear anodised: bright, hard-wearing, does not mark hands or equipment; the standard for touring cases
- Black anodised: popular for stage and broadcast equipment where a low-visibility finish is wanted
- Gold or bronze anodised: premium display, retail and presentation cases
- Powder coated: any colour to match branding; thicker film, good on cases that will be cleaned often
Anodising can be specified to MIL-A-8625 (Type II) or to a film thickness class; for cases that see heavy handling, 15 – 20 µm gives a good balance of wear resistance and cost.
Standards, tolerances and documents
| Item | Standard |
|---|---|
| Extruded profiles, material and properties | ASTM B221; EN 755-1 and EN 755-2 |
| Chemical composition | Aluminum Association registrations; EN 573-3 |
| Dimensional tolerances | ANSI H35.2; EN 755-9; EN 12020-2 for precision 6060/6063 profiles |
| Anodising | MIL-A-8625; ISO 7599 |
| General | ISO 6362 for wrought extruded products |
Slot width and the position of click-on barbs are the critical features; they are checked against the profile drawing with gauges on each production run. Each shipment carries a mill test certificate to EN 10204 3.1, and RoHS or REACH declarations can be provided for case makers who need them.
Where double angle extrusions are used
- Flight and road cases: audio, lighting, instrument, camera and broadcast equipment cases, rack cases
- Transport and storage crates: reusable crates for tools, medical and test equipment
- Display and exhibition: trade-show cases, plinths and showcases
- Enclosures and cabinets: electrical and electronic enclosures, kiosks and machine guards
- Furniture and partitions: panel furniture, partition corners and cleanroom wall corners
- Doors and windows: corner frames that join two glazed or panelled faces
How to order double angle extrusions
- Send detailsPanel thickness and type, leg length, fit type, alloy, finish, lengths and quantity; a sample or drawing helps.
- Confirm the profileWe match an existing die or propose a custom section, and confirm tolerances and the quote on EXW, FOB, CIF or DAP terms.
- Sample checkSamples can be supplied so you can test the fit with your panels before the full order.
- ProduceExtrusion, finishing, cutting and drilling, with dimensional checks on slot widths.
- DeliverFilm-wrapped bundles in cartons or crates, with EN 10204 3.1 certificate, shipped by sea or air.
References and standards
- ASTM B221 – Extruded bars, rods, wire, profiles and tubes (aluminium and its alloys)
- EN 755-2 / EN 755-9 – Extruded profiles: mechanical properties and tolerances
- EN 12020-2 – Extruded precision profiles in 6060 and 6063: tolerances
- MIL-A-8625 – Anodic coatings for aluminum and aluminum alloys
- ISO 7599 – Anodizing of aluminium and its alloys: method for specifying decorative and protective anodic oxidation coatings
Double angle aluminium (aluminum) extrusions: FAQs
What is a double angle extrusion used for?
It joins two panels at a right angle and protects the edge. Its main use is framing flight cases and road cases, but it is also used for display cases, enclosures, crates and partition corners.
How do I choose the slot size?
Match the slot to the measured thickness of your panels, not the nominal size. For example, "3/8 in" plywood often measures 9 – 10 mm. Send a panel sample if you are unsure.
What is the difference between slide-on and click-on profiles?
Slide-on profiles accept a range of panel thicknesses and rely on rivets to hold the panel. Click-on profiles have internal barbs that lock into a groove routed in the panel edge, which needs a closely controlled panel thickness.
Which alloy is used for double angle extrusions?
6063 in T5 or T6 temper is standard because it extrudes the thin slot walls cleanly and anodises well. 6061-T6 or 6082-T6 is used for heavy-duty frames.
Can you supply black anodised double angle in cut lengths?
Yes. Profiles can be anodised black, clear, gold or bronze, or powder coated, and cut and drilled to your lengths.
Building cases or panel frames?
Send your panel thickness, finish and lengths. We will confirm the right double angle profile and a delivered price.
