VIDEO: Basic MIG Welder Tour

In this video, I want to give you an overview of what's called a MIG welder

It's a kind of electric arc welder and the word MIG is an acronym. It stands for

metal inert gas. It is actually the easiest welder for beginners to use. I'm not a professional welder but I've been welding on and off for more

than 30 years and the MIG welder is the thing if you want to get involved in

hobby welding, this is just the ticket because it's so easy to use. So as I

mentioned, it's a kind of electric welder which means that it forms an arc

and the arc during use, as you'll see, travels from this little wire here to

the metal workpiece. And the reason it travels to the metal workpiece is because it wants to complete a circuit. This is called a ground cable and it

also connects to the metal you're welding and it provides a path for the

electricity to flow. So there's an arc jumping in the airspace between this

little wire and the metal you're welding and that arc creates heat. And something

else too, one of the important features of the MIG welder is that it

automatically advances new wire into the weld. So this is just sitting here right

now but if I were to turn it on, it's gonna boot up in a second, you'll see

that that wire actually extends on its own. I'll just press it for a second and

you'll see. Now the reason for that is because most welding involves adding new

metal to the joint that you're connecting and this happens automatically with the MIG welder. The wire comes out, you can adjust the rate at which the

wire comes out, as well as some other parameters on the machine, but this

automatic wire advance is one of the reasons MIG welders are so easy to use

It's also why there's sometimes called wire feed welders because they're feeding the wire in automatically. But let's go around to the front of the

machine now and I'll show you a few parameters and how this machine

is adjusted and used too. There are two main parameters when it comes to a MIG

welder. One of them is voltage, you can see that here. I'm doing some welding

right now, welding some some steel pipe. It's about an eighth of an inch wall

thickness or so and as it turns out, 17.4 volts is what I want. Now voltage on a

MIG welder translates to the intensity of the arc. Now you want that arc to be

intense enough that it melts metal on both pieces that are being joined, but

not so powerful that it actually blows a hole through the metal. So you can see

here, all MIG welders allow you to control the voltage. Now I'm in the

green zone here because I have, as I'll show you, pre-programmed this machine for

the kind of metal that I'm welding. So it's giving me a range of voltages so I

can safely go from 16 volts to 18 volts. This would be too much, that would be too

little given the metal that I've told the welder that I'm welding. So

voltage, one parameter. Now the other parameter is inches per minute of wire

feed travel. So once again I have a range of 261 here, 310 on the top end

and 210 on the bottom end. So 261 is about right. In practice, and I'll get into this

more in subsequent videos, but in practice you want a balance between the

two. It doesn't have to be an identical balance each time. Sometimes you can

crank up the heat voltage more and sometimes you want a little more wire

feed, but those are the main two parameters that all MIG welders need to

be adjusted for. Now how you adjust is different from machine to machine. This

is fairly sophisticated and it's got a digital control so it's basically

infinite control over those two parameters. Less expensive machines you kind of have a preset level for the voltage and wire feed rates. Another big

thing you need to realize when you're talking about MIG welders is the the two

different modes that you can MIG weld in. One is using shielding gas and the other

is using what's called self shielding wire. In both of those cases it comes

down to the simple physical fact that when an arc is occurring, the metal of

course involved is molten. It's very hot, way too bright to look at with your bare

eyes, and in that state, in that heated state, it becomes very reactive with

oxygen. So you can get what amounts to a very fast rusting right in the weld pool

area and you're going to get a terrible weld. There's just no way around it. If oxygen is allowed to encounter the molten weld pool, then you're going to

have a bad weld. So there's two solutions to that. One solution is the

configuration that I have my machine set up here and that's to use an inert gas

So inert means that it doesn't react. An inert gas that floods over the weld zone

while it's molten and it displaces the oxygen. So it protects the weld from

oxygen for that second or two that it's molten as you move along when you're

welding. So in addition to the wire that comes from a spool inside the machine, I

will show you that in a minute, there's also gas traveling through this cable

It's a pretty sophisticated cable really. The gas flows out of these holes here

I've taken this shroud off. The gas flows out of these these holes and out the end

of the nozzle, which you can see is kind of hollow around the outside, and that

gas protects the weld. So this is a blend of argon and carbon dioxide and this is

the shielding gas of choice for welding mild steel. If you're going to be welding

other metals with the MIG welder, you might have to change and go for a

different shielding gas. Now it's kind of a complicated thing though. To have

shielding gas, you don't just need the welder, you also need a regulator and a

hose and you need the tank. Where I live, these tanks aren't available to own. You

have to rent them. They're about $100 a year and it costs about $100 to fill

this tank up. How long does it last? It's hard to put your finger on it, but fairly

long we'll say because there is a lot of gas in there, but it's still a hassle and you have to pay more for a machine that can operate with shielding gas. So

there's another alternative. You don't have to use any gas at all and the wire

that's used is actually hollow and inside the hollow of the wire is a

substance that when it's heated and burns I guess during, well in the arc is

generating some heat, it creates a shielding cloud around the weld zone. Now

it's a little bit smoky. There's no smoke when you use something like this. It's a

little bit smoky and the results aren't quite as good for shielding. So the weld

is not going to look quite as good, but it's still going to look pretty good and

there are many people, hobbyists especially, who just use the self shielding wire. They keep things simple. No gas, no tank rentals, no regulator and

it works just fine. It's not an issue of strength really. It's an issue of appearance. The weld is going to look nicer, neater, smoother, more controlled

when you use the shielding gas. So now I want to show you inside. All MIG welders

have an inside of some kind or another where the spool of wire is stored. So

this is just straight wire as I said because it's designed to be used with

the shielding gas. It's 25 one thousandth of an inch in diameter. This machine can

use 25 thou, 30 thou, 35 thou, even larger I think in some cases, but I find that

the 25 thou to be good for small welding. The bigger wire is suitable when you

have to deliver more metal to the joint, so a bigger joint. Now the self shielding

wire, because it's got that little space in the middle, is larger than 25 thou

It's 35 thou, but it doesn't deliver quite as much metal as a regular 35 thou

wire because it's got that shielding gas stuff inside of it. But let's just switch

on here and I'll show you how it works. So the spools come large like this or

smaller, whatever you like, and as soon as I pull the trigger there's a motor feed

in here that's going to start drawing the wire off the spool and pushing it

all the way through the cable. So you see I... That's the way it works. Now the speed at which it draws wire through the

mechanism is controlled by that wire feed knob I was telling you about before

And if I wanted to change the wire or if I ran out of wire, I would

loosen this off. This comes apart like this and you can see the drive mechanism

in here. It's pretty clever really. See there's the drive wheel. Now this wheel

here, you can see it's got a little groove in it, that groove is suited to

this size of wire. So if I was changing wire diameter, I'd need to take this off

replace it with one that has a slightly larger groove. The actual driving happens

up here. As you see there's a gear here. The gear engages the other side of the

gear right here. There's a motor drive in there and this surface of this top disc

is what drives the wire through. It doesn't seem like it should actually

work, does it? I mean pushing a little wee wire like this all the way through a

cable that could be bent or twisted as you use it, but it works. It works

quite well. Oh, right down here you can see too, another thing. This guide

right here comes off and you see it's for 0.025 to 0.035, so 25

one thousandths of an inch to 35 one thousandths of an inch. That's the size

of wire that this backing plate is suitable for. I use my welder almost

exclusively for welding mild steel, so that's steel pipe, plate, things like that

And you'll probably be the same too, but a machine like this is much more

versatile than that and then this chart shows. So we've got metal thickness here

and then we have the type of wire we're using and the different sorts of metals

that we can weld. So this would be for mild steel. We have some stainless steel

options here and aluminum with the right kind of gun and you can also use this

machine for stick welding, which is kind of just like a regular arc welder in

that there's a holder that holds a welding rod and that rod takes the place

of the wire feed that you see on here. So a lot of variety and in practice you'll

probably settle down and just use, you know, a few of these. Typical thicknesses

you know, eighth inch, three-sixths, quarter inch, three-sixteenths, quarter inch. That's probably what you're going to stick to. Most of the material that we want to

weld in the home shop is like that and it is a bit of a hassle too, to be honest

to change over. I mean, it could take me 15 or 20 minutes to change a kind of a

wire. I don't want to do that all the time, but that's an overview of things

And now I'm going to give you a little welding demonstration and I'm going to

show you not just how the MIG welder works, but also the difference that gas or

no gas makes to the results. So I did two different passes on this test chunk of steel here. The first pass

is from here to here and that's with shielding gas running. And you can see

the weld is quite smooth. I think I would have liked better penetrations or better

melting with the surrounding metal, but the bead itself is quite handsome

looking nice and smooth and solid. The second pass was from here to here and I

shut the shielding gas off, just so you can see the difference that it makes. I

actually started from this end and I don't know if you noticed, but the sound

of the arc changed as I went past about this point. Because there was still some

shielding gas in the hose, but when that was spent, there was just full-blown

oxidization going on here and we lost our regular sort of sound that we want to hear

the frying eggs, frying bacon sound here, and it changed to a much more spattery

sound here. Now, there are some pockmarks in the weld. This weld doesn't actually

look as bad as I thought it was going to. It's not as bad as it sometimes gets

but it's not very strong and it's because there's holes and gaps and little pockmarks

because of that oxidization that's going on. So, there you have it. There's the

basic MIG welding tour and an example of gas and no gas welding