Harold E. Johnson wrote:
Solder strippable wire is also called "Bicelflux wire" and it's a
polyurethane enamelled heat removeable insulation. Long ago, I bought
several small putups from a no longer remembered US supplier, however, among
others, it's available from:

http://www.greenweld.co.uk/acatalog/...melled_49.html

in a variety of wire sizes.

When the insulation is removed with a dollop of molten solder, a toxic gas
is released (in small quantities to be sure) and it ought to be done with
good ventilation in the workplace.

There are two totally different families of enameled wire, and the
original question didn't say which one.

For the pretty-coloured polyurethane enamels, solder stripping is the
way to go. As Harold says, that is how they are designed to be stripped.
Professionals use a solder pot, while the rest of us make do with a big
bead of molten solder on the tip of the iron. Don't use a flame for
solder-strippable wire - it's too hot, and charred polyurethane enamel
sticks to the wire.

Heated for long enough at the right temperature, the enamel comes right
off with no scraping required. The decomposing enamel also acts as a
solder flux, so the stripped end is bright and ready-tinned.

The other type of enamel is usually brown - some of it is your
grandfather's brown lacquer, but the modern stuff is not.

The really old stuff can be charred in a spirit burner (chosen for its
cool flame which doesn't oxidize the copper) and the loose carbon
scrapes off easily. Note: this is the *only* kind of enamel that is
suitable for flame stripping.

The modern brown enamels are totally different. They are mainly intended
for motor and transformer windings, are often double-coated, and are
specifically designed to be heat-resistant and tough as old boots. They
are almost as tough as the copper underneath... and there's your problem
in stripping it.

This stuff laughs at molten solder and spirit burners. Heat stripping is
no good because flame temperatures high enough to decompose the enamel
will also oxidize the copper underneath. As far as I know, the only ways
to remove it are by scraping, sandpapering or filing... all of which are
difficult to do without nicking the copper wire.

So how do the professional winding shops do it?



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek