Crimps not staying - am I using the right type / size ?

5 Nov 2009
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United Kingdom
Hi all,

I'm lowering a socket in our kitchen at the moment and the cable is not long enough (socket was at head height due to being used for a tall fridge freezer)

I've read about extending the cable and how if it's not going to be accesible (i'm going to repair the area where the socket was) then I need to use crimps if I'm going to extend the lead.. so on the advice of this wiki;
I went out today and bought some 2.5mm twin and earth (looks to match the size that is currently installed), some crimps and a ratchet crimping tool.

Now, I've done plenty of crimping in the past on automotive electricals, but according to that wiki if I'm using 2.5mm cable then I should be using the blue connectors, these do not stay on once crimped - they easily slide right off, even if I crimp it down tighter by putting it into the 'red' slot on the crimping tool.

The red butt connectors however fit really nicely and stay on nice and tight once they are crimped.

So, can anyone clarify - do I have the right stuff, and which connectors should I be using ?

This is what I bought:

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Probably the crimps - red ones shouldn't fit onto 2.5mm wire, so if they do, they are not the size they claim to be.
It sounds like you are using the correct crimps and the right tool for the job so it's a bit strange that your crimps are not working.

Can you post a clear close up photo of one of your crimped joints? Use the macro function on your camera if it has one.

My crimper only crimp only crimps the middle 1/4" of the crimp. I wonder if yours is the same and you are inserting the crimps to the wrong side?

I was just about to tell you off for not using the DIYnot wiki, but it seems I haven't written the how to thru crimp page yet :oops:
Or the cable is not 2.5 !!! Can you post a picture of the cable and each end your trying to crimp together and we an look closer at it.

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Blue on the live conductors, red on the CPC. If you find they aren't crimping properly, it's most likely due to a poor quality crimp tool. I have a set of rather crimps that I purchased from B&Q in a moment of madness, and they don't put anywhere near enough force down to achieve a proper joint. Stick to a quality brand such as Weidmuller or Pressmaster.

That said, if you can fit all the conductors into red crimps are they are secure and won't pull out or work loose, there's no harm done.
Two things about the crimping tool;
1, the jaws are the wrong way round ie. the yellow one should be closest to the piviot not the red ones, but that shouldn't make much differance using the blue terminals.

2, the jaws look like a set i've got, and on them one side of the jaw crimps more than the other, so try putting the terminal in the jaws from the other side, looking at them i would say the wire should stick out to the left side if looking at them from the top
You should be able to tell from looking at the inside of the dies which side the conductor should enter.
B&Q crimps are ****e (on 2 occations I've not had any so resorted to the afore mentioned outlet, both times I ended up using terminal block as a temp until I got some good crimps. As you say they look like they are on ok but slip of with the smallest of tugs.....B&Q= carp)
Bin them/take them back for a refund & complain. Then go to screwfix or local wholesaler & get some decent crimps.
This may be of interest from just below halfway down click for the page :- "Making An Insulated Terminal Connection"

See the differing 'die' forms ('die' as in shaped blocks of metal used to form other metals / materials)


Have your work cut out obtaining this 'ideal' cross sectional form (on left) when crimping 'singles' (single stranded cable).

PS. To original poster - you do need to crimp both ends of the 'through' or connector crimp (note the impressed form or shape in this instance ), pix from davelx hereabouts :-


I don't use ratchet crimps that often, but from memory it looks like your jaws are not the correct type for your crimps? Are they for telecommunications industry perhaps? Also you say you got them from B n Q but they are branded JCB; anyone know if these guys make good handtools?
Get a pair of CK crimpers and buy your crimps from a wholesaler, they are much cheaper that way, or ditch crimps and use Wago push fits or Ideal Twisters.

It's been discussed to death in the past, but regardless of your viewpoint on maintenance-free terminals, I'd think you'd be hard pushed to recommend burying either of those in a wall.

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