On Wed, 20 Jan 2021 19:32:10 +0000, John Rumm
wrote:

On 20/01/2021 19:25, Cursitor Doom wrote:
On Wed, 20 Jan 2021 08:55:02 +0000, Muddymike
wrote:

On 19/01/2021 22:34, Cursitor Doom wrote:
Gentlemen,

I need to replace the liner in my MIG welder. The one that's coming
out is the 'bicycle brake cable' type where the welding wire's conduit
is essentially identical to the tightly-wound coil type sleeve you
find on old bikes: a metal liner and thus conductive. The replacement
new one has a PTFE liner. It's much less friction and should feed the
wire more smoothly than the old one. However, I'm left wondering how
welding current is supposed to get to the wire since it will be now
running inside an insulated sleeve. So.... Anyone know?


Power transfers at the tip. Arking in a worn tip causes jerking in the
wire feed.

Mike


It just seems to me like a very tenuous connection to rely on. As the
wire travels through the copper tip there must be some times where
there is no contact at all and even when there is contact with the
tip, the 'footprint' as it were of the contact area is truly tiny for
such relatively high currents ! I'd have expected a system which
relied on that concept to provide only intermittent power to the wire.
:-/

The tip is quite long and should be a fairly snug fit.

Right, so in that case, replacing a metal-sleeved wire conduit with a
PTFE lined one requires no additional modification. Well, we'll see
tomorrow......