Connecting elements are the brackets, connectors and plates that join aluminium profiles. They divide into two families: concealed connectors that sit inside the slot and leave the outside faces clean, and visible brackets that bolt onto the outside of a joint. Choose by joint type first, then by load, then by whether the outside faces have to stay clear.
Below: the four joint types, the hardware options for each, and the load-path rule that prevents most frame failures.
Start with the joint type, not the part
Almost every aluminium frame is built from four joints. Identify which one you are making and the hardware shortlist becomes obvious.
| Joint | Description | Typical hardware |
|---|
| Butt / in-line | Two members meet end to end in a straight run | Linear connector or a joining plate |
| Corner | Two members meet at 90° in the same plane | Anchor connector, die-cast bracket, angle profile bracket or an internal joining plate |
| Tee | One member ends against the middle of another | Anchor connector into the through member, or a bracket plus a plate |
| Cross | Two members cross, either at the same level or one over the other | Cubic connector, or a bracket pair where one member is continuous |
Concealed or visible?
The first real decision is appearance, because it removes half the options.
Concealed joints
A concealed connector sits inside the slot and is tightened through a hole in the profile or from the end face. The outside of the frame stays clean, which matters on furniture, display structures, doors and any frame the customer will see. The cost is that the members need machining — usually an end tap or a counterbored hole — so the frame has to be planned before it is cut.
Visible joints
A visible bracket bolts onto the outside or inside of the corner. It needs no machining, can be fitted with a standard hex key, and can be added or removed on an assembled frame. The cost is appearance and, on the inside of a corner, the space the bracket occupies. Inside-mounted brackets are usually invisible in service and are the pragmatic choice for machine frames.
| Criterion | Concealed | Visible |
|---|
| Outside faces | Clean | Bracket or fastener heads show |
| Machining needed | Yes — end tap or counterbore | No |
| Assembly speed | Slower; needs correct orientation | Fast |
| Retrofit onto an existing frame | Difficult | Easy |
| Typical use | Furniture, displays, doors, visible frames | Machine frames, guarding, prototypes |
The load path rule
Frames rarely fail in the middle of a member. They fail at joints, and they fail because the load is concentrated on a short length of slot lip.
A connector transfers load into the profile through the lip of the slot. The lip is thin, and it is the weakest feature of an otherwise strong section. The rule that follows is simple: never let one connector carry a load that a pair could share.
- At a corner, use two connectors, or one connector plus a joining plate, wherever the frame carries a machine or a moving load.
- At a tee, the through member is being loaded across its slot. Use a plate to spread the load, or fit the connector into the through member rather than the abutting one.
- On a cantilever, the moment at the joint rises with the length of the arm. Two brackets separated along the profile are far stronger than one larger bracket.
- Where a frame vibrates, a joint that is adequate statically will still loosen. Add a second load path, or use a serrated washer and a thread-locking compound.
Practical point: adding a second connector at a corner costs a few cents and a few seconds. Replacing a frame that has moved under load costs the whole build. When in doubt, over-specify the joints and under-specify the profile.
The accessory families
Anchor connectorsConcealed corner and tee joints. Tightened from the end face or through a hole, leaving the outside clean. See anchor connectors.
Die-cast bracketsCast corner brackets that bolt into the slot. Fast to fit, available for every standard series. See die-cast brackets.
Angle profile bracketsExtruded or machined L-brackets for heavier corners and for retrofitting a brace. See angle profile brackets.
Joining platesFlat plates that span a butt joint or reinforce a corner, spreading load over a long length of slot. See joining plates.
Other connecting elementsCubic connectors, end connectors, screw connectors and linear bar connectors for the joints the standard range does not cover. See other connecting elements.
Fastening elementsT-nuts, hammer nuts, flange nuts, bolts and washers — the hardware every joint also needs. See fastening elements.
Materials and what they mean
Brackets are made from die-cast zinc, die-cast aluminium or steel, and the material affects how the joint behaves.
| Material | Behaviour | Use it when |
|---|
| Die-cast zinc | Strong and dimensionally accurate; heavier than aluminium | General structural corners at standard loads |
| Die-cast aluminium | Light; slightly lower strength; anodises to match the frame | Appearance matters and the load is moderate |
| Extruded or machined aluminium | Strong in the direction of the extrusion; heavier section | Heavy corners and long brackets |
| Steel, zinc plated | Highest strength; different colour from the frame | High-load joints where appearance is secondary |
Common mistakes
- Mixing series. A 30 series bracket will not seat on a 40 series profile. Slot width and bolt centres both differ, and the same trap exists between 40 and 45 series.
- Using a bracket as a structural member. A bracket joins two profiles; it does not replace a diagonal brace. Where a frame needs stiffness, brace it.
- Forgetting the fastener. A bracket is only half the joint. The T-nut, the bolt length and the washer matter as much as the bracket, and bolt length is series-specific.
- Overtightening. Torquing a small slot beyond its limit crushes the lip permanently. Use the fastener maker's figure rather than tightening by feel.
- Assuming a corner is square. A corner joint aligns two members but does not guarantee 90°. Assemble on a flat surface and check the diagonals.
How to specify joint hardware
The fastest way to order is to send the frame layout and the series. From that we can list the connectors, plates, fasteners and quantities, which is usually quicker and cheaper than ordering part by part. If you already know the parts, give the series, the joint type, whether the joint is concealed or visible, and the quantity. Standard hardware is quoted within one working day. Related ranges: strut profiles, 30 series, 40 series, profile accessories and panel installation elements.
