MIG Welding - A Beginners guide. (With 8 part Video)

This article is designed as written piece associated with my eight part videos section on the same MIG welding subject. It should be treated as a guide only and not as advice. Please ensure that you consult your operators manual for the safety recommendations.

MIG welding is so called because it describes a weld process whereby the molten weld pool is protected from the atmosphere whilst it solidifies by a shroud of inert gas. This gas is usually a mixture of CO2 and Argon.

For the beginner, it is the process which uses a torch with the filler wire feeding through the torch into  the weld pool. It is usually employed in a workshop environment and could be used to weld anything from car body work right up to heavy steel buildings and fabrication work.

The components in the setup are as follows;


1. The power source of the welder.

2. The bottle of shielding gas and a regulator.

3. A wire feeder which is the mechanism which feeds the wire along a torch. (The power source and the wire feeder can be either two separate pieces or they can be combined into one machine)

4. The torch which includes a torch body and a connecting tube from the wire feeder. This is a special tube which houses a liner inside through which the mig wire is pushed, another tube, along which travels the shielding gas and a power cable which imparts a current into the mig wire when it exits the torch body at the welding end. There are also a couple of low voltage switch wires from the torch back to the wire feeder which trigger the feed motor to run and the gas to flow when a trigger is pulled on the torch.

5. An earth lead which is connected to the power supply at one end and the work piece at the other end to complete an electrical circuit when the trigger is pulled.

6. A power supply that is rated at the correct size for the welder that you are going to use. If the welder is rated at 13 Amps then you are probably ok to plug into a domestic supply. If however it is rated at something like 32Amps then you need to be sure you are plugging into the correct socket. You will soon blow the trips if you wire a 13Amp plug onto a lead that should be 32Amps or worse still, you could cause a fire by over heating a socket so be sure you know what you are doing.

So you have bought your MIG welder and you are ready to have a go at joining two bits of steel plate together.

Your check list should be;


1. Gas. Assuming you have you got the correct type and have you enough in the gas bottle?

2. MIG wire. Hopefully you will have been given the correct type and diameter (mm) for the welder you have purchased.
Do not try to use any wire that has gone rusty. The rust will come off in the torch tube (the liner) and very quickly
choke up the liner so that it causes you problems.

3. Welding mask and possibly a pair of welding gloves. The mask should have a dark glass in it with a shade value
of between 9 and 13. The 11 shade is usually suitable for low amperage welding settings when you are trying to weld
sheet metal (car bodywork). The more amps and generally the thicker metal you are welding will push you up the
shade scale into 12 or maybe even a 13 shade glass.

4. Your test bits (clean steel with no paint or rust) on a bench of some description which is not going to catch fire.
Watch out that there is nothing imflammable around or near you weld area as the sparks can fly a long way.

5. You have the correct size plug wired on the power supply lead and its plugged into the correct size socket.

6. Connect the earth cable clamp on the earth lead onto the piece you are going to weld.

7. Connect your regulator onto the gas bottle ensuring you nip it tight but not over tight.Unscrew the pressure gauge knob if you have one before you turn on the bottle. If your regulator has gauges on it then it may have up to
two pressure gauges on it. One will be the pressure in your bottle ( How full your bottle is). The other will be the  pressure setting that you are going to send your shielding gas along to the torch at. As a general rule of thumb, I
would set my pressure at about 12 LPM (Litres per Minute) Some regulators are pre set with no gauges whatsoever and if you have one of these you just need to turn it on. Obviously we are assuming that the supply pipe is connected
from the regulator to the welder otherwise all your gas will just escape into the atmosphere. Silly!

8. Before you turn on the welder at the on/off switch you will need to feed the MIG wire through a set of drive rollers in the wire feed unit and then along your mig torch cable and lastly into the torch body and out through the tip in the welding end of the torch. This can be a bit tricky but go steady and don't force anything and you should be ok. The wire feed end will have a post which you mount the mig wire onto. You usually have to unscrew a retaining nut on the end of the post to allow you to drop your roll of mig wire over the post. You then reposition the retaining nut which is usually hand tight only. Make sure you have got the mig wire roll on the right way so that when you are ready to find the end of the mig wire you can carefully feed it into a guide or small hole in the back of the feed unit.
It will then follow a straight line from the underside of the roll of wire, through the small hole and towards the drive roller mechanism. There is usually a lever with a spring tension that has to be released so that the two drive rollers
move apart and allow you to feed the mig wire between the rollers and into the small hole in the end of the torch
tube (liner).  
You might have to then pull the shielding shroud off the end of the torch body and unscrew the mig tip. This tip will be like a small nozzle with a tiny hole in the centre of it where the mig wire is supposed to come out from when
you are welding. Carefully feed the mig wire along the torch connecting tube until it pokes out at the torch body end. When you have successfully managed all that and you can screw the tip back into the end of the torch and push
the shroud back into its place.
Before you close the two drive rollers, try to pull through some wire through the  liner. It should be easy to pull. You can now close the drive rollers and just tension them slightly.
So you should now have the wire mounted and fed through into the torch end. The tip and shroud have been put back onto the end of the torch and a small length of mig wire is poking out of the nozzle/tip.
Now turn on the machine and with the wire feed setting knob turned to a very low speed you can try and pull the
trigger on the torch.
The wire should move out of the torch very slowly. The ideal setting for the tension on the drive  rollers is when you can just hold the mig wire from coming out of the torch end by squeezing the wire between your
fingers and it slips on the rollers. Increase the tension on the rollers by turning the screw on the top roller until it just overcomes your fingers.

Now you are ready to try a weld!!


Adjust the power setting on your set to suit the job. Let us say you are about to try to weld together some sheet metal (2mm thick)

Depending on how powerful your set is, you won't need too much power for this.Turn the setting down to low and set the wire speed (if you have the facility) to the middle setting.

Try it on a piece of scrap. If the torch is jumping around and bucking in your hand then the wire is too much for the power so adjust the wire speed down a bit and re try it.  Keep doing this until you can keep the end of the torch about 12mm away from the work piece and the weld sounds
smooth and crisp and even.

There you are!! off you go!!

  


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