Cast corner brackets
A die-cast bracket is a cast corner piece that sits in the slot on both faces of a joint and is fixed with two or three bolts. It needs no machining, fits with a hex key, and is the fastest way to build a square aluminium frame. This page covers the materials, when the casting becomes the limiting part of a joint, and how to use brackets well rather than just often.
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A die-cast bracket is a cast corner piece shaped to fit into the T-slot of two profiles at a joint. It is fixed with two or three bolts and needs no machining of the profiles, which makes it the fastest and most forgiving way to build a bolted aluminium frame. It is available in sizes matched to each series, in die-cast zinc or die-cast aluminium, and in internal and external forms.
Below: how the casting behaves compared with a machined bracket, where the design limit sits, and how to use brackets so that a frame is stiff rather than merely assembled.
The bracket is an L or a triangular gusset with a ribbed profile. It drops into the slot of each member, and bolts through the bracket into T-nuts in the slot draw it tight. The ribs are what make the casting work: they carry the bending load from one leg to the other without the bracket needing to be solid.
Two features separate a good bracket from a poor one, and neither is visible in a photograph.
| Material | Strength | Weight | Finish | Use it when |
|---|---|---|---|---|
| Die-cast zinc | Higher | Heavier | Bright or coated; different colour from the frame | General structural corners at standard loads |
| Die-cast aluminium | Moderate | Light | Can be anodised to match the frame | Appearance matters and the load is moderate |
| Machined or extruded aluminium | Higher in the extrusion direction | Light to moderate | Matches the frame | Heavier duty and visible joints |
| Zinc-plated steel | Highest | Heaviest | Plated; distinct colour | High-load joints where appearance is secondary |
Cast brackets are deliberately the weakest part of a bolted joint, and that is not a defect. A bracket that fails before the slot lip is crushed protects the profiles, and profiles cost far more than brackets. But it does mean the bracket sets the ceiling on the joint.
Three signs that a die-cast bracket is at its limit:
Practical point: on a heavy frame, use a die-cast bracket for assembly and alignment, and add a joining plate for strength. The bracket pulls the corner square quickly; the plate carries the load. This combination costs very little more than two brackets and performs far better.
| Type | Where it sits | Advantage | Watch out for |
|---|---|---|---|
| Internal corner bracket | Inside the corner, in the slot | Invisible in service on most frames | Occupies the inside of the corner; can clash with a panel or a drawer |
| External bracket | On the outside faces | Nothing inside the frame; easy access to the bolts | Visible, and it uses the outer slot that a panel may need |
| Tee bracket | At a member end meeting a through member | Simple way to build a mid-span joint | Loads the through member's slot across its width; add a plate where load is high |
| Angled bracket | Inside a corner, at a set angle | Allows frames that are not rectangular | Usually a bespoke casting; check availability for your series |
A frame with a bracket at every corner is not automatically a good frame. Four habits separate a well-built structure from one that merely assembles.
Brackets are only half the joint. The T-nut, the bolt length and the washer matter just as much, and all three are series-specific. A bolt that is too long bottoms out in the slot before the bracket is tight; a bolt that is too short engages too few threads and strips under load. Where a bracket is fitted into a slot that already carries other hardware, check that the T-nut positions do not compete — two items cannot occupy the same point in a slot. The full hardware range is described under fastening elements.
Give us the profile series, the joint type, whether the bracket is internal or external, the material and the quantity. If the joint carries a machine or a cantilevered load, say so — that is the point at which we would recommend a machined bracket or a plate instead of a standard casting. Standard brackets are quoted within one working day. Related ranges: connecting elements, anchor connectors, angle profile brackets, joining plates and fastening elements.
FAQ
A cast corner piece shaped to fit the T-slot on both sides of an aluminium profile joint. It is fixed with two or three bolts and needs no machining of the profiles.
For standard corners, yes. Where a corner carries a machine, a cantilevered load or vibration, use a machined bracket or add a joining plate so the load is spread along the profile.
Zinc brackets are stronger and heavier. Aluminium brackets are lighter and can be anodised to match the frame. The choice is usually about load and appearance.
Usually because the joint is being worked by a load it was not designed for. Add a second load path, check the bolt length, and use a thread-locking compound on dynamic structures.
Internal brackets are invisible in service and are the usual choice. External brackets leave the inside clear and give better access to the bolts.
Use every position the bracket provides. Leaving positions empty concentrates the load on fewer points and is a common cause of a joint that moves.
Yes, a washer under the bolt head spreads the load and protects the bracket. Serrated washers also help resist loosening under vibration.
No. Bracket sizes are matched to a series because the slot width and bolt centres differ. A 30 series bracket will not seat correctly on a 40 series profile.
Send the drawing, the section size or a sample and we will confirm the alloy, the tolerance, the finish and the commercial terms. Quotes for standard items normally go out within one working day.
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