Types of cable lugs and terminals, and how to crimp them correctly

The main types

Tube lugs also come in different wall thicknesses and barrel lengths, for example standard and DIN 46235 types. Use the type your crimp tool maker lists for its dies.

Matching the lug to the conductor and the stud

Two sizes define a lug: the conductor size (mm²) and the stud hole (for example M8, M10, M12). The barrel must match the conductor cross-section exactly; a larger lug crimped onto a smaller conductor does not compress properly. The hole must match the terminal bolt, and the palm must fit the terminal width. The same 95 mm² lug is made with several hole sizes, so always state both.

Check also the conductor class: lugs for stranded (class 2) conductors may not suit highly flexible (class 5 or 6) conductors; some makers offer lugs for flexible cable. Never use a copper lug on an aluminium conductor: the metals corrode where they meet.

Insulated terminals and ferrules

Pre-insulated terminals follow a common colour code by conductor size: red about 0.5 to 1.5 mm², blue about 1.5 to 2.5 mm², yellow about 4 to 6 mm². Crimp them with a ratchet tool made for insulated terminals, which does not release until the full crimp is done.

Bootlace ferrule colours are not the same in every system, so order them by the size printed in mm² and crimp them with a ferrule tool (square or trapezoidal profile).

Crimp tools and dies

Tube lugs are crimped with mechanical or hydraulic tools using hexagonal dies marked with the conductor size (and sometimes a die code). The die must match both the lug size and the lug type the tool maker lists. Indent (point) crimping is used by some systems, but only with the lugs and tools designed for it.

The number of crimps and their order along the barrel depend on the lug size, the tool and the die width: follow the lug or tool maker's instructions. Pliers, hammers and wrong-size dies give crimps that look tight but heat up under load.

Step by step

• Cut the conductor square, without damaging strands.
• Strip to the barrel depth, so the conductor reaches the end of the barrel with no bare conductor left between insulation and lug beyond what the maker allows.
• For aluminium, clean the strands with a wire brush and use oxide-inhibiting compound (many aluminium and bimetal lugs are supplied pre-filled).
• Insert the conductor fully, with no strands folded back or cut away.
• Crimp with the correct die until the dies close fully, the number of times the maker specifies.
• Remove any sharp edges, fit heat-shrink or insulation, and bolt to the terminal at the torque the equipment maker states.

Inspecting the crimp

A good crimp shows complete die marks with the size code readable, no cracks in the barrel, no strands outside, and no movement when pulled by hand. Compression connectors for power cables are qualified to IEC 61238-1 as a combination of lug, die and tool, which is why mixing makers' dies and lugs is risky. During maintenance, a thermal camera scan of loaded panels finds poor terminations before they fail.

Heat-shrink over lugs

Heat-shrink sleeving over the barrel and the cable insulation seals out moisture, insulates the barrel and can carry the phase colour. Size it so its expanded diameter slides over the largest part and its recovered diameter is smaller than the smallest part it must grip. Our heat-shrink sizer does this check.

What to send us for a quotation

Conductor size and material (copper or aluminium), conductor type (stranded or flexible), stud hole size, quantity, and whether you need standard or heavy-duty lugs. Add the crimp tool you already use so we offer lugs and dies that fit it, or ask us to quote the tool, the dies and heat-shrink on the same offer.

Common questions

This guide is general information. Final selection must follow the project design, the applicable standards and the maker's data.