To which Jeff replies -

Using a battery to weld CAN be done.  ALWAYS disconnect both 
cables from battery, stray electrons can fry unintended objects.

As for the starting voltage being higher.  Not exactly right.  On 
most welding machines a high frequency current is generated to assist 
in starting the arc, then backs off.  Starting without the high freq 
is tricky, but doable.  It's called a scratch start, one starts the 
arc by scratching the workpiece with the weld rod to generate an arc, 
then welding sustains arc, distance between weld rod and workpiece 
regulates power.  

Just plunging in there results in a great big short, with your weld rod 
welded onto the workpiece, overloading the circuit and hopefully 
shutting you down.  Using a raw battery would result in destruction of 
the battery, boom.  This is not for the timid, this is not for the weak
minded, this is as a last resort.  Check with serious 4WD people, 
this is something they do, and use for serious troubles in the boonies.

Flux core is well suited for automated welds, weld operators, 
and is supplied on a coil. Don't think it would be sturdy 
enough as a hand held electrode.  Works well for a point and shoot 
weld setup.

Shielded rod is usually around 12 inches long, coated with flux 
except for about 2 inches to attach to the clamp.  Would not work for 
a point and shoot weld setup, flux would crack off going through 
rollers, drive gear, etc.

- Jeff

> Jeff Carver writes:
> > SMAW = Shielded Metal Arc Weld, aka stick welding.  A solid metal rod 
> > with flux on the outside surface.  Well suited to large welds, weld 
> > suited to field repairs.  A VERY good welder can do thinner 
> > materials.   Can actually be done using a car battery (not while
>                ========================================                       
> > running though).  Weld rods are relatively short, not on a coil.
> 
> Never thought of this. Get the jumper cables out. Hook up one to the
> object, one to the welding rod. Pang, boom, Done!!! Free and portable 
> arc welder. (Bonus: only need one cable when welding on same vehicle!)
> 
> Has anybody tried? I was under the impression that the voltage
> to start the arc is a lot higher than 12v in a typical welding
> transformer. When started voltage drops. Any tricks to vary
> the current? (Yeah, I know: el cheapo jumpers = low current,
> premium...)
> 
> /Martin (flunked welding 101)
> 
> btw Why the difference between FCAW and SMAW? I thought I've seen
> sticks in both varieties (flux on the outside or in inside channels),
> and that there isn't much difference in use.