Ferrules - can they go over the wire sheath?

CinSen · Jan 20, 2023

I'm replacing a threaded lamp holder and the original wires had ferrules on the end so I'm replicating this as it seems like it ensures a more reliable grip between the contacts.

Given that the entry point for the contacts will create a 90 degree bend in the wires, I think that the kink will be a weak point which, over time, could cause the wire to break off, which is what appears to have happened previously.

My 'solution' is to apply the ferrule partly over wire sheath itself to minimise the risk of the wire breaking.

Does this approach seem sensible, or am i being an idiot?

westward10 · Jan 20, 2023

So is that ferrule over the insulation.

mattg4321 · Jan 20, 2023

Awful idea if it’s over the insulation

DPG · Jan 20, 2023

CinSen said:
I'm replacing a threaded lamp holder and the original wires had ferrules on the end so I'm replicating this as it seems like it ensures a more reliable grip between the contacts.

Given that the entry point for the contacts will create a 90 degree bend in the wires, I think that the kink will be a weak point which, over time, could cause the wire to break off, which is what appears to have happened previously.

My 'solution' is to apply the ferrule partly over wire sheath itself to minimise the risk of the wire breaking.

Does this approach seem sensible, or am i being an idiot?View attachment 105496

No, don't do that. The ferrule just goes over the copper wire.

Darkwood · Jan 20, 2023

That is a poor crimp if over sheath but given the load and why we use crimps it's not really going to be detrimental as the terminal it goes in has a clamping effect, we simply use these on flexes to stop stray strands or terminal damage to the fine wires.

MJPD29 · Jan 20, 2023

Terrible idea. Its for the copper only

timhoward · Jan 20, 2023

If there is concern about the cable bending, and there is space, a bootlace ferrule might be a better option.
These can be trimmed in length and even slightly angled (if you want to copy my questionable bad habits that is!)

Lucien Nunes · Jan 21, 2023

As above, not keen on that. Granted, your intention would be to make sure that the part of the ferrule clamped in the terminal is the part over the stripped conductor not the insulation, but I don't think it will gain you anything in terms of supporting the cable. I could imagine that any flexing will cause the ferrule edge to chew the insulation and make an even sharper transition to the bend.

Use a bootlace type as above, or a plain ferrule with a short piece of heat-shrink sleeving bridging from the last few mm of the ferrule to the insulation as a bend relief. It must bridge that gap, if it was just on the insulation and not gripping the ferrule, it would make things worse. If there is limited space behind the terminal for the cable to bend, and there is flexure, you might find that anything you add makes it worse by increasing the necessary bend radius, and it was best how it originally was.

brianmoooore · Jan 21, 2023

Heat shrink, as Lucien suggests above. Often use it on things like crimped on ring terminals as well, to make it look that bit tidier and a little safer.
Helps that I aquired a few hundred metres of the stuff for free, a few years back.

littlespark · Jan 22, 2023

For the load on a lampholder, I don’t think a 90 deg bend is going to cause much problem.

Old filament lamps, causing heat within a fitting, or moisture getting in and rusting the metal would be bigger issues.

I know I’m talking fractions of a mm here, but to get the crimp to go over the insulation, you’ll need a size bigger than the one for just going over the conductor…. So when you crimp it up, there will be excess material.
It may not crimp against the conductor as it should.

CinSen · Jan 22, 2023

Thanks all - that was quite unanimous! I picked up some insulated bootlace ferrules as suggested by timhoward, however there wasn't enough space, so opted for Lucien's solution and used some heatshrink.

Cheers