Key Takeaways
What the marking means. KL25/10 identifies a tin-plated copper cable lug for a 25 mm² conductor with a 10 mm bolt hole; “KL” denotes the lug family.
What the extra code means. “4RH0” is a factory traceability mark; it does not change electrical or mechanical ratings.
Tools that matter. Proper installation requires matched crimping tools and dies—typically hydraulic for larger sections, calibrated ratchet for smaller.
How many compressions. Short barrels or small sections often use one compression; longer barrels and larger sections commonly use two (or more) per manufacturer guidance and DIN/IEC practice.
Why it’s important. Correct crimping delivers a low-resistance, mechanically secure joint that stays reliable under load.
Story & Details
Reading the stamp.
A lug marked KL25/10 tells a compact story. The “KL” family label appears widely in European catalogues for tubular copper lugs; “25” signals a 25 mm² conductor; “10” is the bolt-hole diameter. These lugs are typically made from seamless copper tube and supplied tin-plated for corrosion resistance. After stripping the conductor to the barrel length, the wire is inserted and the barrel is compressed to form a gas-tight, high-pressure contact that is then bolted to a stud or busbar.
The secondary line.
Marks like “4RH0” are production identifiers. They support quality tracking—lot, tooling, or line—without altering the lug’s size, hole, material, or rating. Traceability marks are common across reputable catalogs and standards-aligned data sheets.
Tools and dies—not pliers.
Crimping is controlled deformation. For mid to large cross-sections, installers use hydraulic heads or battery tools with interchangeable dies; for smaller sizes, calibrated ratchet hand tools are typical. Matched die codes and profiles—frequently hexagonal for DIN 46235 lugs—help ensure the finished connection meets pull-out and heating requirements set by international standards.
One crimp or two?
The visible imprints on the barrel vary by size, barrel length, and crimp profile. Manufacturer guidance and DIN practice indicate a single compression can suffice on short barrels and smaller sections, while longer barrels and larger sections are typically finished with two compressions spaced along the barrel; very large sections may require more. Many DIN 46235 lugs even carry small guide marks that show where each compression should land.
Finishing the joint.
After crimping, heat-shrink is often applied for strain relief and moisture protection. The goal is a low-resistance, vibration-resistant termination that stays cool in service—something only a correctly tooled compression can achieve.
Conclusions
Clear markings, clear method. KL25/10 conveys the essentials: conductor size and stud size. The extra stamp is for traceability.
Discipline over improvisation. Use the matched tool and die, follow the lug’s markings, and apply the number of compressions appropriate to the barrel and cross-section.
Reliability is engineered. When crimp geometry, material, and process align, these small parts carry big currents safely for years.
Sources
- Klauke — “Compression cable lugs according to DIN 46235.” https://www.klauke.com/se/en/compression-cable-lugs-according-to-din-46235
- Klauke — “Assembly instructions for cable lugs and connectors” (PDF). https://www.klauke.com/Media/Default/Downloads/TechnicalAppendix/processing-connecting-materials.l-en.pdf
- Klauke — “Connection technology and crimp profiles” (PDF). https://www.klauke.com/Media/Default/Downloads/CatalogsBrochures/BRFACH19GB_Klauke%20Fachwissen_02_2019_I_GB.pdf
- IEC — “IEC 61238-1-1:2018 overview.” https://webstore.iec.ch/en/publication/29515
- BSI Knowledge — “BS EN IEC 61238-1-1:2019 summary.” https://knowledge.bsigroup.com/products/compression-and-mechanical-connectors-for-power-cables-test-methods-and-requirements-for-compression-and-mechanical-connectors-for-power-cables-for-rated-voltages-up-to-1-kv-i-u-i-sub-m-sub-1-2-kv-tested-on-non-insulated-conductors
- Nexans — “Compression cable lugs, copper, DIN 46235 (KU/KU-V).” https://www.nexans.de/en/products/Power-Accessories/Conductor-connectors-and-cable-lugs/Compression-cable-lugs/Compressio27595.html
- YouTube (TE Connectivity) — “The Basics of Crimp Quality.” https://www.youtube.com/watch?v=0I1ZVXoB8Yk
Appendix
Crimp profile. The geometry created by the die—often hexagonal for DIN 46235 lugs—chosen to deliver uniform pressure and low contact resistance.
Die code. A marking on the tooling and, after crimping, sometimes impressed on the lug to confirm the correct die was used.
DIN 46235. A German standard defining applications, dimensions, markings, and processing guidance for copper compression cable lugs.
IEC 61238-1-1. An international standard specifying type-test methods and requirements for compression and mechanical connectors for low-voltage power cables.
KL25/10. A common product-style marking indicating a tubular copper lug for a 25 mm² conductor with a 10 mm bolt hole.
Traceability code. A secondary factory mark (for example, “4RH0”) used for production and quality tracking; it does not alter electrical or mechanical specifications.
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