Crimp terminals and butt sleeves join wires by pressing them with a tool instead of soldering. Crimps can all look alike, but a poor one may pull out under vibration or tension, or make poor contact and heat up. Here is what you can check by eye and by hand on site.
Match three things before you crimp
- Terminal and wire Each terminal is made for a set wire cross-section (SQ). Allpum insulated ring terminals cover 1.5–6.0 SQ and butt sleeves 1.5–4.0 SQ. Wire thinner than the range ends up loose; thicker wire will not fit the barrel.
- Tool Use a crimping tool and die cavity suited to the terminal type (bare or insulated) and size. Squashing it with pliers is not a crimp.
- Stripping Strip the insulation to the length of the crimp barrel without nicking or cutting strands. Twist the strands lightly so they go in as one bundle.
What a good crimp looks like
- The conductor goes all the way through the barrel; the strand ends are just visible at, or reach, the front of the barrel.
- On bare terminals no insulation is inside the barrel, and the bare gap between barrel and insulation is short.
- On insulated terminals the wire insulation reaches inside the insulating sleeve, so no bare conductor shows.
- No strands are left outside the barrel.
- The crimp mark sits evenly in the middle of the barrel, with no cracks in the barrel or tears in the sleeve.
- Holding the wire and the terminal, a hand pull or twist does not move it.
Spotting a bad crimp by its symptoms
| Symptom | Common cause | What to do |
|---|---|---|
| Wire turns in the barrel or pulls out | Under-crimped, die cavity too large, or wire too thin | Re-crimp with the right terminal and cavity |
| Split barrel or broken strands | Over-crimped or die cavity too small | Cut off and redo with the correct cavity |
| Insulation trapped in the barrel | Insulation stripped too short | Re-strip to barrel length and use a new terminal |
| Strands outside the barrel | Strands not twisted together | Twist the strands and use a new terminal |
| No conductor visible at the front | Wire not fully inserted | Insert fully and use a new terminal |
| Torn or pierced insulating sleeve | Tool or cavity meant for bare terminals | Redo with a tool for insulated terminals |
Joining wires with a butt sleeve
Insert a wire from each end of the sleeve so they meet in the middle, then crimp each half separately. If one wire goes past the middle, the other has less length to grip. Allpum sleeves come in 15 mm (M) and 30 mm (L) lengths, so choose one with room for two crimps. Sleeves are bare metal, so insulate the joint afterwards where needed.
A quick on-site routine
- With a new terminal and tool combination, crimp a few on spare wire first and look at the result.
- Check each crimp against "What a good crimp looks like" above.
- Give it a hand pull to make sure nothing moves. Where a pull-force requirement applies, follow it and the tool maker's instructions.
- Cut off any doubtful crimp and redo it on the spot.
Crimp quality depends as much on the size you choose and how you work as on the terminal itself. For choosing tip shapes and sizes, see our guide to crimp terminal types; dimensions and wire ranges are in each product's specification table.
