How to crimp a bootlace ferrule
Updated: 23 October 2026
You have a ferrule in one hand and stranded flex, and the screw in the terminal looks as if it will finish the job. It will not. This is how to crimp a bootlace ferrule so the strands stay in one tube before they ever meet that screw: match the mm², strip to the pin, seat the collar if there is one, close a ferrule tool until it releases, then tug. If the conductor moves, cut that ferrule off. The five kits on the [ferrule comparison](/hub/diy-supplies/ferrule) are ferrules only. A qualifying purchase can earn us a commission at no extra cost to you.
You have a ferrule in one hand and stranded flex, and the screw in the terminal looks as if it will finish the job. It will not.
You have a ferrule in one hand and stranded flex, and the screw in the terminal looks as if it will finish the job. It will not. This is how to crimp a bootlace ferrule so the strands stay in one tube before they ever meet that screw: match the mm², strip to the pin, seat the collar if there is one, close a ferrule tool until it releases, then tug. If the conductor moves, cut that ferrule off. The five kits on the ferrule comparison are ferrules only. A qualifying purchase can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Insulation | Conductor range | Crimping tool | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  WeqeYent WeqeYent 1000-piece non-insulated wire ferrules | Non-insulated | 0.5–16 mm² | No | 8.2 | about £10.99 | View offer |
| Best value |  Newoutset Newoutset 800-piece non-insulated wire ferrules | Non-insulated | 10–22 AWG | No | 8.8 | about £5.88 | View offer |
 flintronic flintronic 1500-piece insulated wire ferrules | Insulated PVC collar | 0.5–10 mm² | No | 8.9 | about £8.99 | View offer |
What the crimp is for
Fine strands under a screw spread, and a screw can cut the ones at the edge. A bootlace ferrule is a soft metal tube that you close around those strands so they enter the terminal as one pin. The IET's Wiring Matters mythbuster puts a crimped bootlace against regulation 526.9 as the treatment for a screw terminal, and says you crimp before you insert. The screw clamps a pin that is already made. It does not form the pin.
A ferrule that is the wrong size, or a tube you push in without crimping, can be worse than bare strands under the same screw. The tool has to be a ferrule crimper, not a red, blue and yellow insulated-terminal tool.
Prepare the conductor
Cut the end square so every strand reaches the mouth together. If the ferrule is insulated, the plastic collar faces the insulation and the metal pin faces the terminal. A 1.5 mm² flex takes a 1.5 mm² ferrule. EN1508 means that cross-section with an 8 mm pin. EN1512 is the same cross-section with a 12 mm pin. The terminal depth chooses between them. One size up crimps loose. One size down will not take the strands. Which size to buy is on the bootlace ferrules buying guide.
Strip so the bare copper fills the metal barrel and the insulation sits at the collar, or at the mouth if the ferrule is bare. BuildWiz gives 8–12 mm as a domestic rule of thumb for common 1.0–6.0 mm² ferrules, not a figure in BS 7671. A light twist keeps the bundle in the funnel. A hard twist can snap the strands.
Crimp and check
Put the metal barrel in the jaws, not the plastic collar. The collar is a funnel. It is not the part the die is meant to squash. Close a ratchet ferrule tool until it releases. If your tool has marked nests, use the nest for that mm². A self-adjusting ferrule tool still does not correct a 2.5 mm² barrel on 1.0 mm² flex.
Look at the pin before you insert it. The strands should not fan out of the mouth, the barrel should not be split, and the collar, if there is one, should still sit on the insulation. Then tug. If the conductor slides or comes out, that ferrule is scrap. Cut it off and start with a new one. A hand tug is a stop rule for a joint you can remake. It is not a type test.
What to leave alone
Do not solder the whole fine-stranded end and put that tinned block under a screw. The IET states regulation 526.9.2 as a ban on that practice, because solder can cold-flow and the joint relaxes. Do not crimp with ordinary pliers. They flatten the tube and do not release at a set point. Do not let the terminal screw finish the crimp. By the time the screw meets the barrel, the strands should already be trapped.
Stop and call a registered electrician when the tug has failed, before you energise, when you cannot identify the terminal, or when the work is inside a consumer unit. A board change and other notifiable work under Part P are not a ferrule tutorial. Where a consumer unit is the wrong place to practise is on bootlace ferrules for a consumer unit. Ending a visible flex in a screw on the bench is the job this page describes.
Common questions
How long do I strip the wire?
Long enough for the bare copper to fill the metal barrel, and short enough that insulation is not inside it. BuildWiz's 8–12 mm span is a rule of thumb for common domestic ferrules from 1.0–6.0 mm², not a BS 7671 dimension. If strands stick out in a brush, you stripped too far. If the collar will not meet the sheath, you stripped too little.
Can I use ordinary pliers?
No. Pliers flatten the tube and give you no release point, so a ribbon of metal can look finished and still let the strands pull back. A red, blue and yellow crimper is the wrong die as well. Use a ferrule tool until it releases, then tug. None of these five kits supplies that tool.
Can I let the terminal screw finish the crimp?
No. The IET's instruction is to crimp before you insert. The screw clamps the pin. If you rely on the screw to close the tube, strands escape beside it and the screw can cut them. Total Connections describes that fan of strands as the reason bootlaces are used.
Is soldering the end still allowed?
Not as a whole tinned end in a screw terminal. The IET states 526.9.2 that way: solder can creep, and the joint slackens. A ferrule you have crimped and tugged is the treatment for fine strands in that screw. Soldering the ferrule onto the wire is a different joint, and it is not what these kits are for.
How do I know the crimp failed?
The conductor moves when you tug, the barrel is split, strands fan out of the mouth, or the collar is mashed into the metal. A Gorffy reviewer could crack a thin tube by wiggling the boot even after a pull held, so look at the tube as well as the tug. Cut a failed ferrule off.
When do I stop and call an electrician?
When the joint is in a consumer unit, on a new circuit, or on any notifiable Part P job, and when a crimp pulls off on a circuit you were about to energise. Also stop if you cannot prove the conductor is dead. Changing a board is not the job this page describes.
Related pages
Sources
Public UK sources and the amazon.co.uk listings compared on this page. Listings captured 21 October 2026. Updated October 2026.
- IET Wiring Matters, Mythbuster #5 (March 2020) (retrieved 22.10.2026)
- Weidmuller UK: wire end ferrules (retrieved 22.10.2026)
- Phoenix Contact ferrule guide (retrieved 22.10.2026)
- RS PRO crimping kit 513-2540 (retrieved 22.10.2026)
- GOV.UK: competent person schemes (retrieved 22.10.2026)
- Electricity at Work Regulations 1989, regulation 4 (retrieved 22.10.2026)
- BEAMA consumer-unit guidance (retrieved 22.10.2026)
- amazon.co.uk listings B0C7GJX239, B0D8PNZSPK, B0CCTJMQ9Q, B0F8B11BC8, B09T9425PF (retrieved 22.10.2026)