Aluminium Extrusion Connector System for 20×20 to 100×100 mm T-Slot Frames

Four questions, asked in this order

The order matters. Asking them in a different sequence leads to a joint that works structurally but cannot be serviced, which is the worst of both worlds.

The five families compared

Read that table as a set of trade-offs rather than a ranking. The screw connector is the cheapest and the neatest, and it is the one you cannot take apart. The end face connector is the strongest and it needs the end of the profile to be machined. The bracket is the most flexible and the most visible.

When to choose each one

Visible bracket — the default for anything that will be modified

A die-cast or angle bracket bolted through the slot is the joint you can undo with a hex key on a finished frame. That makes it the right answer for guarding, workstations, shelving and anything that is expected to change. The angle profile brackets range covers the small sizes from 35 x 35 x 4 mm upwards, and the die-cast brackets cover the moulded corner pieces with a locating spigot that sits in the slot.

The limit is appearance and stiffness. A bracket is in bending across the corner, so the joint is never as rigid as a connection that puts the member end in compression. On a frame that has to hold a machine tool position, a bracket corner will move under load.

Inner bracket with top thread — the answer for visible frames

An inner bracket slides into the groove of both members and a set screw is driven down onto the groove floor to jam it in place. Nothing shows on the outside. It is available with M5, M6 and M8 threads to suit 6.2, 8.2 and 10.2 mm groove cavities, so one design covers the 20, 30 and 40 series. On a display frame, a door frame or an enclosure where every face is seen, this is the only family that gives a completely clean surface without machining the profile ends.

Cubic connector — three members at one node

A cubic connector is a solid block with bores on three faces, used where three members meet at a corner. Because the block is in compression rather than in bending, the node is far stiffer than three brackets would be, and it uses fewer parts. The 20 series version is a 20 x 20 x 20 mm cube with three 14.5 mm bores and a 26 mm centre; the 45 series version is 45 x 45 x 45 mm on the same geometry. A clip-on ABS cap covers the exposed face.

Screw connector — the cheapest hidden joint

A screw connector is driven into the core hole at the end of one profile and forms its own thread in the aluminium. It is the cheapest way to hide a joint, and it is the least forgiving. Re-using the formed thread more than two or three times loses its grip, so it belongs on a frame that is assembled once and left alone. Use it on production frames, not on prototypes.

End face connector — the strongest hidden joint

An end face connector bolts into a tapped hole in the end of the profile, with a spring clip to hold the position while you assemble. Because the bolt is in tension into the section rather than in shear through the slot, the capacity is set by the thread rather than by the groove. This is the joint to use wherever a member is pulled, wherever the frame has to be rigid, and wherever a bracket has already proved too flexible. It shares the design space with the anchor connectors, which do the same job with a different locking mechanism.

Mixing families on one frame

A real frame uses two or three families at once, and the rule for combining them is simple. Put the stiff, hidden joints where the load is and the brackets where the adjustment is. A typical machine guard frame uses end face connectors or anchor connectors at the four base corners, brackets on the panel-retention nodes, and inner brackets on the one face that the customer sees.

The one combination to avoid is mixing a screw connector with anything that expects to be re-tightened. Once a self-tapping connector has formed its thread, the joint is effectively permanent, and treating it as adjustable is how a frame ends up with stripped threads in the core hole.

Frequently asked questions