Ferrules on flexible cable used for permanent wiring

[Nikki Locke]

Presumably this doesn't apply if you use tinned cable? (i.e. cable where the whole length of the wires was already tinned when you bought it).

[Dave Osborne]

Not the same thing at all. In tinned cable, the individual copper strands are coated with a microscopically thin layer of tin plate (or, in the case of expensive mil-spec stuff, nickel or silver plate. Only after plating are the individual strands made up into a multi-strand wire.

Tinning the end of a wire involves stripping the end back, usually lightly twisting the individual strands together to neaten, and then covering the whole exposed area with solder, thus consolidating the individual strands into a solid.

Now, solder exhibits a metallurgical property called "cold flow". If you tin the end of a wire and then trap the end under a screw, the pressure that the screw exerts on the solder will cause the solder to flow away from the pressure point. Over time, this gives the effect of having a loose screw and the integrity of the termination is compromised as a result.

So the tinning of wire ends destined for screw terminals is not only

*not* recommended, it is to be actively discouraged.

[Nikki Locke]

OK, so you shouldn't tin cable that is going in to a screw terminal. But the OP implied that you shouldn't tin wires at all. What's your expert opinion on the other kinds of connection you find in a boat - crimped spade terminals, crimped battery terminals, etc. ?

[tinnews]

Same, don't do it. If you tin leads and then crimp them the solder will creep and the crimp will come loose. If you want to solder connections then solder them but mixing solder with other connection methods that have been engineered to work without tinning/soldering is not a good idea.

[tinnews]

That's not the same thing.

Tinned cable is just separate copper strands each if which is covered in a thin layer of tin, still separate.

Tinning the end of a stranded cable (whether or not it was already made of tinned copper wire) is wetting all the strands with solder and thus making them all stick together into a single mass.

[Derek Moody]

Perhaps I didn't make myself clear - don't tin and then screw down - solder direct or else solder/crimp to a tag and screw that down.

Cheerio,

[Tim Lamb]

In message , Derek Moody writes

Umm.. again. My experience was with industrial electronics in the '60's

- '70's. Numerous failures were found where soldered tag connections fractured at the solid to stranded interface. Strapping cable looms and otherwise avoiding flexure at this point helped.

Terminations have moved on a lot since then:-)

regards