Cable lugs for 1.5 to 630 mm²: a sizing table

A size chart is a starting point

A cable lug chart usually lists a conductor range, a stud size and a barrel type. That is enough to order a sample, not enough to release a joint. The chart does not know the conductor class, the terminal spacing, the fault current, the ambient temperature or the crimp die on your press.

The range from 1.5 to 630 mm² covers control wiring, machine power, distribution boards, switchgear, transformers and heavy feeders. The physics changes across that range. A 1.5 mm² lug is dominated by handling and strip length. A 630 mm² lug is dominated by conductor weight, palm stiffness, crimp force and heat.

Use the chart to narrow the family, then check the five columns that matter: conductor, stud, barrel, palm and die. The rest of this guide walks through those columns and the way they change by size band.

A chart also says nothing about the weight of the finished lug or the stiffness of the palm. At the top of the range, those are handling and assembly issues, not footnotes. A part that is correct on paper can still be difficult to hold, align and torque in a cabinet.

Read the conductor correctly

The nominal area in mm² is the starting point, but the class is the next question. IEC 60228 defines conductor classes from solid and stranded through to flexible. A Class 2 stranded conductor and a Class 5 flexible conductor of the same area have different strand counts and different bundle behaviour. The flexible bundle compacts more under the die.

Strand count matters as much as the area. A 95 mm² conductor made from many fine strands needs a barrel that contains the bundle without cutting strands at the entry. A coarse stranded conductor of the same area needs a barrel that can accept the larger individual strands and still compact them.

If the cable is compacted, tinned or made to a manufacturer-specific stranding, the nominal chart may not apply. Make a sample with the actual cable and the production die. The chart is a map, not the territory.

The five columns that decide the part

Conductor: the area, the class and the strand count. Stud: the thread and the terminal surface. Barrel: the bore, the length and the wall. Palm: the hole pattern, the width, the thickness and the angle. Die: the crimp tool and the height window. If any one of these is missing, the selection is incomplete.

The stud size is often copied from the cable size, which is backwards. The stud belongs to the device: a breaker terminal, a busbar, a transformer pad or an earth bar. The lug palm has to fit that stud and the space around it. The cable only decides the barrel.

The die is the column most often left out of a chart. A lug that is listed for a 120 mm² conductor still needs the die that matches its barrel and the actual conductor class. The die number should be on the drawing and in the work instruction, not inferred from the cable size.

1.5 to 16 mm²: control and small power

At the small end, the joint is easy to crimp and easy to get wrong. The strip length is short, the strands are fine, and a barrel that is one size too large can let the conductor pull out. The bellmouth and the insulation support matter more than the pull-out load, because the cable is often moved during assembly.

A standard tubular barrel is usually enough. A long barrel adds crimp area but also adds length, which can be a problem in a crowded terminal block. Choose the palm for the device: a ring for a stud, a pin or a blade for a terminal block, a fork only where the screw will stay tight.

Inspection should focus on the strip length, the insertion depth, the bellmouth and the crimp height. A pull test at the setup stage is enough for most small joints, provided the height is checked through the run.

25 to 95 mm²: distribution and machine power

This is the working range for distribution boards, machine feeders and small switchgear. The conductor is stiff enough to load the palm, and the crimp force is high enough to expose a die or wall problem. The long barrel becomes useful because it gives room for two crimps and a more uniform compaction.

The palm often moves to two holes in this band. A two-hole lug fixes the orientation and shares the clamp load, which helps under vibration and during a fault. It also needs a terminal with matching hole spacing, so the palm and the device have to be chosen together.

At 95 mm² the difference between a flexible and a stranded conductor is visible in the crimp. Check the section for voids and strand damage, and check the pull test across the actual conductor class, not just the nominal size. A die that suits one class can be marginal on the other.

120 to 300 mm²: switchgear and transformers

At this size the lug is a structural part as well as an electrical one. The conductor weight and stiffness load the palm, and the crimp requires a press with enough force and a die that closes evenly. A long barrel and a two-hole palm are common because the joint has to carry fault current and resist vibration.

Wall thickness and concentricity become critical. A thin wall on one side can crack under the crimp force, and a crack that is invisible from the outside can become a hot spot. Section a sample at qualification and measure the wall at four points.

The palm face has to be flat enough to sit on the terminal. A lug that rocks on the pad has a smaller contact area, and the bolt torque may not close the gap. Check flatness and burrs around the hole as part of the incoming inspection.

400 to 630 mm²: heavy feeders

The largest sizes are used on transformer connections, heavy distribution feeders and high-current equipment. The crimp force is high, the tooling is heavy and the handling is a task in itself. A 630 mm² copper conductor is stiff enough that the lug orientation has to be set before the crimp, because moving it afterwards loads the barrel.

Two-hole palms are normal. The palm thickness and the hole spacing have to match the terminal, and the bolt class has to be adequate for the joint. The contact surface should be flat and clean, with the correct plating pair for the bar material.

Inspection should include a section, a pull test and a temperature rise check on a qualification sample. The section shows whether the die compacted the full bundle, and the temperature rise shows whether the joint has margin at the rated current. A visual check alone is not enough at this size.

What the chart cannot tell you

The chart cannot tell you the conductor class, the die, the crimp height, the plating thickness, the terminal spacing or the fault current. It also cannot tell you whether the lug will fit the space around the stud. Those calls need the drawing and the device.

A chart that lists a range for a barrel is a statement about the barrel, not about the joint. The joint is proved by the die, the height, the pull test and, for critical parts, a section and a temperature rise test. Treat the chart as the first filter, not the release.

If the cable is aluminium, stop and decide the transition strategy before choosing a lug. Aluminium needs a different barrel, a different preparation and usually a bimetallic joint at a copper terminal. A copper lug chart does not cover that decision.