"Ignoramus28225" wrote: (clip) I thought that connecting different secondary
windings in parallel would be some sort of equivalent of a short.(clip)
^^^^^^^^^^^^^^
If the windings have the same number of turns, and you don't get the
polarity reversed, they don't act like a short.

A "stick" welder has to have inductance in addition to the transformer
itself, so that while you are welding, the current remains relatively
constant. Particularly, while you are striking the arc, you are shorting
the welder output. Without the extra inductance, the current would jump way
up, possibly sticking the rod and turning it red hot.

I think building a welder is an interesting challenge, but if you try to
weld with an unknown and imperfect setup, you won't know which part of the
problem is the machine, and which part is you. I agree with the others who
say you should start by buying an inexpensive unit.

Do you know about sci.engr.joining.welding?