How to Tack Weld
The Voice: Hey, Kevin. What are you doing?
Kevin Caron: Well, I got an email the other day from Sandy in Columbus, Ohio, who is going to school to learn how to weld. She's an artist like me; a sculptor. She asked, "How do you decide between tacking something and just flat welding? Where do you draw that line, and what in the heck is tacking anyway?"
Well, I thought, that's a good idea for a video. Let me show you.
I'll begin with some pieces of eighth-inch steel plate that I've pulled out of the scrap bucket. I've just cut some little pieces, and I'm going to tack them together to make a little box, then I'll show you what to do.
Here's my Miller 251 MIG, set at 19.8 volts and 289 inches of wire. What I want to do is just hold these together (with the gloves, of course), and get a couple of little tacks on there, just to hold the metal - stop it from moving, so you can get another piece in place and adjust it a little.
Afterwards you can step back to look at it. Basically, it gives you a third hand, another set of arms to help hold something while you're trying to get everything all jigged up and put together.
Here's a good tip for you: this MIG has a 25-foot hose on it. When it sits overnight, it loses the gas out of the hose. It just leaks out naturally from the end of the hose. When you go to weld with it first thing in the morning; if you don't bleed the oxygen out of it - bleed the air out - you get the inert gas back in again, and you'll get this ugly-looking little weld.
So, what I do the first time I turn it on in the morning as I'm about to weld with it is, run one, two, three worth of wire out of the end of it. That helps purge all of the oxygen, or the atmosphere, out of it. Now it's full of inert gas again. Then you can either cut that off with wire cutters or snap it off on the end of the table.
So, put your helmet on. Let's take a look at this.
Because I'm welding on this big one-inch-thick table, I can put a little more of my heat down on the bottom piece. (tack welding)
And that's a tack. That's all it is: just to get a little spot here, a little spot there. Now the metal is going to sit there while you come back in with another piece. Let me see, we'll add that one, and that one.
Gloves. You gotta love 'em.
Let's try this one over here. Now you just get it close, get it right where you want it. (tack welding)
And you snap it on there. Now you can just keep going; you can assemble some fairly decent-sized pieces, just by putting little tacks in them.
If it's not structural; if it's just to "hold a little feather on a bird" or something like that, then, yes, it's just a little tack. That's all you?ll need, a little zap. If you're going to put a big, long, heavy piece on, then, yes, you're going to want to tack it. Wherever the metal is moving, and you want to stop it from moving; give it a little tack. Then you can come back and get your whole big long weld across there.
So now, if I was going to finish up this job, I would come back and weld in between; go over, get it on the other side, and grind it down. Then it would be smooth; ready to go. We'd have a nice little; I'm not sure what that is - we've got the beginning of a little sculpture or something going on there.
I hope that answers your question. Bye.
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