How to mig weld part  3: Mig welding consumables

Mig welding consumables are called a consumable because as you use them they are used up (consumed).

Some of the main welding consumables on a mig welding machine are.

Contact tips

Contact tips are designed to carry an electrical current that originally came from the main power supply and transfer it to the welding wire. At this point in the electrical circuit the power is at a contact point. Because it is at the end of the gun or the tip, you put the two words together and you get contact tip. The mig wire is also called an electrode because it carries electricity.

There are different styles, shapes and sizes of contact tips for mig welding. The most important part is that you match the wire size to the correct hole size of the contact tip. So for .035" (0.9mm) wire you would use a .035" (0.9mm) contact tip. There will be a marking on the side of the contact tip that will say what size it is. For aluminum wire you need to use a slightly larger tip size to help prevent feeding issues. Often people use large tip holes sizes for flux cored wires as well.

A quick tip: I you are having trouble feeding wire, maybe it's a bad batch of mig wire try using the next size up tip. This has often worked for people before.

The more power you run the machine at, as in the higher the amperage the lager the physical size of the contact tip. Also the longer the tip the better the electrical conductivity. This is because there is more surface area for the wire to make a better contact.

Welding nozzles / shrouds

The welding nozzle, or as it is sometimes called the shroud slips over the end of the gun covering the contact tip. It's job is to (only when using shielding gas) contain the welding gas around the welding arc. If you didn't have that nozzle there all the gas would come out of the end of the gun and float off in the air from the welding arc. This is why mig welding outdoors can be a bit troublesome when it is windy, as it blows the gas away. Even in a workshop you will find they have to shut the shed doors on mildly windy days.

Gas diffuser / insulator / tip holder

Depending on what brand of welding torch you have such as a Binzel Bernard, Tweco or OTC. They all have different diffuser, insulator and tip holder setups.

The basic idea here is that you need to somehow hold the tip on the end of the mig welding gun and hold the nozzle on as well. Some guns will have a white ceramic diffuser that is also an insulator as well. You need to electrically isolate the welding nozzle from the rest of the "live" welding gun. If you don't, you find that because the shroud is live every time you bump into the metal you are welding it will spark and arc onto the nozzle.

The gas diffuser is either part of the insulator, part of the tip holder or a separate part by itself. Either way all three items here do the same thing.

The gas diffuser has a series of holes about 2mm (0.080") in diameter that go around the circumference of it. It is designed to make the welding gas come out evenly so that it flow around the contact tip as opposed to just one side of it. The tip holders job is the do just that, hold the tip in place. The welding gun liner will butt up to it on the opposite end of where the tip screws in.

Liner

Inside the guts of the mig welding gun is the welding liner. It is there to provide the welding wire a place to travel from the feed rollers to the contact tip. Liners are bought to suit a specific range of welding wire diameters. For example if you are running 0.9mm wire most liners will cover wire sizes from 0.9mm to 1.2mm. If you have a gun cable that is 10ft long you buy a liner that is 10ft long. Sometimes you can only get say a 15ft liner. Then all you do is cut is shorter to suit. They look like if you were to take a pencil and wind wire around it along it's length. Like a compressed spring. Except that they are not as thick at the diameter of a pencil, but you get the idea.

Normal liners are made from steel and are called a steel liner. If you plan on mig welding aluminum you will need a teflon or plastic liner. These are supposed to have less friction so that it is easier to feed the wire through.

Liners need replacing every so often. They are one of the most neglected items on a wire welding machine.

In part 4 of the how how to mig weld series we take a look at the mig welding wire choices available for welding with.

How to mig weld. Part 4. Mig wire.