Aluminium cable lugs, crimped onto the conductor and bolted to the terminal
A compression terminal sized by three numbers: conductor, palm hole spacing, stud diameter. Made here from wrought aluminium, with the heat-cycle reports to go with it.
An aluminium cable lug is a compression terminal: the conductor goes into a barrel, a die closes around it, and the joint holds by cold weld rather than by solder or screw. It is the standard termination where a compression tool is available — overhead line to transformer, cable to switchgear, jumper to bushing. Specify it by the conductor, the palm hole pattern and the stud size; the catalogue number follows from those three.
What the drawing has to say
A lug that is dimensionally wrong is scrap, and it is scrap in the most annoying way: it arrives, it looks right, and the palm holes are 4 mm off the terminal. These are the dimensions that have to be on the enquiry, in the order that matters.
| Dimension | Where it comes from | What goes wrong if it is wrong |
|---|---|---|
| Conductor size and stranding | The line schedule, not the drawing | Barrel too small will not take the strand bundle; too large crimps loosely and runs hot |
| Palm hole spacing (centre distance) | The equipment terminal, measured | The lug will not bolt flat, or bolts only on one hole and tilts |
| Stud / bolt diameter | The equipment terminal | Hole too small will not pass the stud; too large loses contact area |
| Palm width and thickness | The terminal pad and the current rating | Overhangs the pad or under-connects the current path |
| Barrel length | The die set your crews carry | Barrel may need two crimps where the die only covers one |
| Material and temper | The specification | Hard temper cracks at the crimp; soft temper deforms under clamp load |
Send the terminal as a photo with a rule across the palm if there is no drawing. It is faster than a thread of messages about hole centres.
Where aluminium lugs actually fail
Not at the barrel, usually. Three failure modes account for almost every hot joint we are asked about.
The oxide film. Aluminium oxide forms in minutes and is an insulator. If the conductor is not brushed and inhibited immediately before crimping, the crimp closes on oxide and the resistance starts high — and rises. This is why the compound matters as much as the die.
Under-crimping. A die that is one size off, or a press that is worn, gives a joint that looks crimped and pulls out at half the specified load. Compression is a measured operation: the die has to match the barrel, not the conductor alone.
The galvanic couple. Aluminium lug on a copper busbar, outdoors, no bimetallic plate. The aluminium corrodes preferentially and the joint fails from the outside in. If the equipment terminal is copper, say so at enquiry — the answer is a tin-plated lug or a bimetallic palm, not a thicker lug.
Standards and what they test
Three standards come up in tenders, and they test different things. Knowing which one your utility applies shortens the approval.
| Standard | Market | What it actually proves |
|---|---|---|
| GB/T 14315 | China, and projects written on GB | Dimensions and performance of compression lugs and connectors for cable conductors |
| IEC 61238-1 | Europe, Middle East, Africa, most World Bank work | Heat-cycle and short-circuit performance of compression and mechanical connectors |
| ANSI C119.4 | North America | Heat-cycle class for aluminium-to-aluminium and aluminium-to-copper connectors |
Heat cycle is the test that matters commercially: it is the one that predicts whether the joint survives ten years of load variation. Ask for the report pages covering your conductor class — they are held and sent with the quotation.
Ordering
Lugs are quoted per size against the die list, so the answer arrives with a part number. Where a size is not on the list, a new die is quoted separately and remains a project cost, which is the honest way to price a one-off.
Tin plating, inhibitor sachets and marked packaging for site issue are all available and all quoted as separate lines, so you can see what each one costs rather than finding it inside a unit price.
Buyer questions
Crimped lug or bolted connector — which should I specify?
Crimped if the crew has a press and the joint will not be re-opened. Bolted if there is no press on site, if the joint has to come apart for testing, or if the work is done live from a bucket. The electrical performance of a correctly made compression joint is more consistent; the bolted one is more forgiving of site conditions.
Can I use an aluminium lug on a copper busbar?
Only with a bimetallic interface — a tin-plated lug or a copper-aluminium transition plate. Bare aluminium against bare copper outdoors will corrode at the joint and run hot. Tell us the terminal material at enquiry and it is priced in.
What die do I need?
The die matches the barrel, not the conductor size on its own. Send the barrel diameter from the drawing and we will tell you which standard die profile it is made to.
Do you supply the crimping tool?
No. Tools and dies are supplied by the press manufacturers, and matching a die to a barrel is a dimensional question we answer on the drawing rather than by selling hardware.
Is tin plating necessary?
Indoors, on aluminium to aluminium, no. Coastal, substation, or anywhere the joint meets copper or humid air for twenty years, yes — and it is usually a line item in the specification anyway.
Related
Send the conductor and the palm pattern.
Cross-section and stranding, plus the hole spacing and stud size from the terminal — the rest follows from the die list.