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Hi Jon. 1/4 inch rod is BIG stuff. I've used it a few times and it takes a
lot of power to run. The issue is really one of control. 1/4 inch rod has so
much power going through it, it vibrates. When I'm "out-of-position" like
upside down, hanging onto an I beam, I need one hand to hold on with. In the
flat position, I use two hands to hold the stinger. It really pushes a lot of
power! I've only used it on structures made of 1 inch steel and thicker,
and only because we didn't want to carry the heavy MIG machine way out on
the structure. You won't see many guys using it anymore. Mostly all field
welding is done with wire feed boxes powered by weld generators on the ground.
You simply run the stinger cable up to where you are and plug the wire feeder
into it. I just hate dragging the wire feed box way out on a bridge or
skeleton of a building if I'm just welding a few brackets on.
With a 1/2 inch thick tank or vessel, 1/4 inch is of no use. 1/8 inch is
the basic rod for most applications, requiring multiple passes. Keep in mind
that multiple passes is a good thing. One welding rod will only lay down a bead
about 3 inches long. When you begin the next pass over the top, you alternate
the stop/start spot so they don't line up with the beads you're
covering. Typically with a grooved seam on 1/2 inch joints, your first root
pass is fairly straight with maybe just a tiny bit of "weave" to make sure you
"wet out" both sides equally. Then the next pass runs along one side tying
the root pass and one side of the groove together. The next pass is from the
other side of the groove, down to the root and just slightly over the previous
pass, tying all three together. As you lay down beads, the groove is
getting wider, so more of a "weave" is used to tie everything together. By the
time you get to the top of the groove, you're "weaving" quite a bit and of
course the weld bead is shorter because it's been "weaved" back and forth. Now
the cover pass is laid over it all, going about 1/8 inch beyond the edge of the
groove and weaving back and forth across the whole thing. You'll learn all about
that in welding class. Again, it takes lots of practice.
As for "back grinding" it's a necessary step for quality
welds. Mostly the only place it isn't used is on pipes, because you can't
get to the back side. When you weld a psub seam, the root is first. then you
fill and finish the groove. The exposed part of the root on the inside will have
a bit of slag on it, and also the exposed layer of the bead will be contaminated
with oxygen from the air. Unlike the outside where you were welding, the
amount of "cover gas" produced by the burning coating on the electrode ( rod )
doesn't reach the back side of the weld. A little slag will gather there, but
the slag has solidified and the gas doesn't reach back there. To get a good
cover pass on the inside, you gotta grind it out to clean metal and get all the
bits of slag and "burned" metal out. By burned I mean the very top layer
exposed on the base of the root pass that had oxygen on it. It's only a few
molecules thick and comes right off with a grinder.
Back grinding also shows you where maybe the root pass didn't "wet-out"
completely or had a slag "inclusion" in the weld puddle. Gotta grind the back
side down to a nice clean groove so the cover bead goes on smooth and isn't
burying anything nasty in there.
You'll learn about that too, in class. Have fun and ask you instructor lots
of questions. Frank D. Great deals on Dell's most popular laptops - Starting at $479 |