"Calvin Henry-Cotnam" wrote in message
om...
Andrew Gabriel ) said...

You should not solder stranded wire prior to putting it into
a screw terminal. Solder creeps under pressure, so the contact
pressure will steadily reduce over time until it forms a bad
contact.

The only place I ever use stranded wire with screw terminals is in
a lamp, and I have on occasion tinned the end first.

I find the creep problem very bad and screws and stranded wire are
a bad mix. I have had a few instances where #14 or #12 stranded wire
was pulled through a conduit, so instead of trying to attach it to
a screw terminal, I would pigtail a short piece of solid wire to it
and attach it to the terminal.


Strands which are tinned during the cable manufacture
are OK, as the solder layer thickness is controlled and very thin.

That reminds me of a lecture I once attended. The speaker was telling
of an experience with a company he was working with back in the 1960s
when they got a project related to the space program. They all had to
be "schooled" in procedures such as soldering, which seemed beneath them
at the time.

The thing that stuck out in my mind was part of NASA's standards: when a
stranded wire was tinned or soldered to a terminal, you should still be
able to count how many strands it has.


Reminds me of ET-Maintenance school in the military. Spent literally a
*week* learning/practicing on just how to solder to bi-furcated and turret
terminals.

We too had to be able to count the strands after tinning. And how much
insulation to strip off so that no more than 2 mm of conductor was exposed
after attaching to terminal. And no melted insulation, and... and... and...
There was something like 14 checks for each soldered terminal connection.

Was bad enough on the bench, but then doing it laying on your back reaching
up inside a cabinet with just a drop-light to see by. Now *that* was fun
(NOT!!!).

daestrom