Ring crimp terminals come in two forms with the same tip: bare terminals, whose crimp barrel is exposed metal, and insulated terminals, whose barrel is covered by a PVC insulating sleeve. Both connect a wire to a stud, but they differ in size range, length, tooling and finishing. Here is how to choose, based on the Allpum specification tables.
How they differ
| Item | Bare ring terminal | Insulated ring terminal |
|---|---|---|
| Crimp barrel | Exposed metal | Covered by a PVC insulating sleeve |
| Wire size | 1.5–10 SQ | 1.5–6.0 SQ |
| Stud size | 3–8 mm | 4–6 mm |
| Sizes | 14 | 11 |
| Overall length L, e.g. 2.5-4R | 16.0 mm | 21.0 mm |
| Crimping tool | Tool and cavity for bare terminals | Tool and cavity for insulated terminals |
| After crimping | Insulate separately where needed | The sleeve covers the crimp |
Where insulated terminals fit
- Close to other terminals On terminal strips and in panels where terminals sit side by side, the sleeve keeps crimps from touching each other.
- Where hands may reach If hands or tools may reach the connection during inspection or servicing, it is better that the crimp is not exposed.
- When separate insulation is a hassle Crimping also finishes the insulation over the crimp, so there is less tubing or taping to do terminal by terminal.
Where bare terminals fit
- Heavier wire, larger studs Allpum insulated ring terminals go up to 6.0 SQ and 6 mm studs. For 10 SQ wire or an 8 mm stud, use a bare terminal (10-6R or 10-8R).
- Tight spots needing a shorter terminal For the same size, a bare terminal is shorter because it has no sleeve. A 2.5-4R, for example, is 16.0 mm bare versus 21.0 mm insulated.
- 3 mm studs The 1.5 SQ bare range includes a size for 3 mm studs (1.5-3R).
- Where insulation is specified separately Where the wiring calls for the crimp to be covered separately, for example with heat-shrink tubing, crimp a bare terminal and finish it as specified.
Because a bare terminal leaves the crimp exposed, insulate it or keep clearance wherever it could touch another terminal or metal part. Match the tool to the terminal type, too: crimping an insulated terminal in a bare-terminal cavity can tear the sleeve, and crimping a bare terminal in an insulated-terminal cavity can leave it under-crimped.
Choosing in four steps
- 1. Wire size (SQ) The first number in the size name is the wire cross-section (1.5, 2.5, 4.0, 6.0, 10). Above 6.0 SQ, go bare.
- 2. Stud diameter The second number is the stud size in mm. A 4.0-5R is for 4.0 SQ wire on a 5 mm stud.
- 3. Insulation Decide whether the crimp may stay exposed or will be insulated separately, then pick insulated or bare.
- 4. Tool Get a crimping tool and cavity that suit the terminal type you chose.
Cap spare wire ends
Cover any wire end left without a terminal with a terminal cap so no conductor is exposed. Allpum terminal caps come in four sizes — 1.5, 2.5, 4.0 and 6.0 SQ — each in red, blue, yellow, green and white, so you can match the wire size and tell circuits apart by colour.
For choosing between ring, fork, blade and disconnect tips, see our guide to crimp terminal types; for checking that a crimp is done right, see our crimp quality guide. Dimensions for each size are in the product specification tables.
