Mig Welder Parts

These are the basic welding consumables and items that you will need for a mig welder.

If we break the machine down into parts we find that there are a few main components that we need to know how to maintain, and what their purpose is. We will start with the front end of the machine which will be the mig welding gun.

Mig gun

This is a Profax brand copy of a Tweco size No.4 MIG welding gun

This one is a genuine OTC 350amp welding gun

On smaller DIY mig welding machines quite often the mig welding gun will be proprietary to that specific model of machine. This means that they are usually hardwired into the front of the machine, and they don't have a quick connect socket. This means that you can't use the more common industrial type of mig welding guns with these smaller machines. Because these smaller DIY type machines are mass produced as the saying goes you get what you pay for. You might also find it may be difficult at times to find spare parts for those brand specific welding torches. Industrial type mig welding guns will have what is called a Euro fitting. The Euro fitting is the industry standard connection fitting for mig welding machines and welding guns.

Shroud / Nozzle

On the front of your mig welding done you are going to have what's called a shroud or a nozzle. This will usually just pull off or unscrew depending on which brand and model of welding gun you have. The purpose of the nozzle is to focus the shielding gas at the welding arc. This gas needs to be contained as close to the welding arc as possible. If you didn't have a nozzle the gas would float away into the air and it wouldn't shield the welding arc like it should.

Contact tip

Underneath or inside the shroud is the mig welding wire coming out of the gun itself. Mig wire is a consumable, this is because it is consumed as you use it. It's also an electrode as it carries electricity. This wire melts and fills in the gap where you need to weld and joint steel together. Directly before the mig wire comes out the wire must pass through a contact tip. This contact tip (or contact tube if you are in the UK), is there so that it can transfer the electricity from the tip to the wire. That's why it's called a contact tip.

Basically it's a small piece of copper that has been turned down on a cnc machine. It has a hole running through the center of it for the wire to pass through. At one end it can have a thread for screwing into the mig gun or it could have a cam lock type design. To install the cam lock type of contact tip it's just a simple matter of giving it a quarter of a turn with pliers until it locks in tight. Contact tips are available in different hole sizes for different wire sizes. Special contact tips are needed for aluminum welding which have a larger hole clearance. Mig welder contact tips are very commonly replaced mig welder parts.

Contact Tip Holder

Behind the contact tip is the contact tip holder, it accepts the contact tip and holds it in place. Depending on brand and model of welding torch, tip holders can be either single function or dual function items. Single function ones are just there to hold the contact tip in place. Dual function tip holders hold the contact tip in place and also have a gas diffuser built into them.

Gas Diffuser/ Insulator

It is also required to electrically isolate the welding shroud from the tip holder body. This is because the tip holder body has live power running through it. Some model mig guns have a gas diffuser that is ceramic and also acts as a insulator. If the welding nozzle was live, every time you would bump into the metal work piece with the sides of the shroud it would arc and spark. Then it would get stuck to onto the metal. Some will have the insulating ceramic pressed into the inside of the welding nozzle, WIA for example. When you slip the shroud over the tip holder it will then give electrical isolation. Tweco mig guns model numbers 2 and 4 have a black plastic insulator. Binzel MB24 and MB36 have white ceramic or rubber insulators/gas diffusers. OTC have ceramic insulators/diffusers or also offer high temperature versions made from plastic.

The single function ones will have another part called the gas diffuser which slips over the tip holder. These are usually a white ceramic gas diffuser/insulator. As they are made out of ceramic they can handle the heat and are offer electrical insulation between the nozzle and the tip holder.

Gooseneck / swan neck

The gooseneck or the swan neck is the part on the gun that is after the plastic handle. The neck of the gun is usually bent at about thirty to forty five degrees. The gooseneck is there so that it can smoothly bend the welding wire downwards so that it is in a good comfortable position when you are welding.

There are a few different styles of goose necks available for most brands of welding guns. The main differences are the angle of the bend in them. The angle of the bend will just allow better access to areas you need to weld into. A good idea if you are mig welding aluminum is to use a neck that has a thirty degree bend as this will have less resistance on the softer aluminium welding wire, and it will feed easier.

Goosenecks are also available which are dead straight which are used for machine welding applications. And example would be using a Koike Weld-Handy device which is a welding tractor that crawls along and positions the welding torch at the weld area. Fully flexible necks are also available which allow you to bend it this way or that way for much better access to hard to reach spots.

Mig Gun Liner

Inside the whole length of the mig welding gun is a mig liner. The liner is a length of steel wound conduit that is fitted into place and has the welding wire running inside of it. The steel liner looks like the same stuff that they use in flexible drive shafts for whipper snippers, and it also looks the same as the flexible white plastic coated springy cord that you can hang curtains from.

Liners are available in different sizes and lengths. The deal is that you buy a liner that is as long as, or longer than your welding cable. If it is longer than you need, you just use some pliers and chop some off the end. The liner will travel starting from the welding machine euro connection (or whatever connection there is) to the back of the contact tip holder. The firmness of the steel liner will allow safe passage of the mig wire and help prevent feeding issues.

You can also get plastic or teflon liners. These are used for when you have to feed aluminum wires. This is because the wire is very soft and the metal liners have more friction in them than the plastic ones. Some brands and models of welding guns will have a two piece kit. For example the OTC Daihen WT3510 torches have a small length of liner for the neck of the gun and then a longer length for the rest. You also need to use the proper sized liner for the wire. So use a 0.9mm (0.035") liner for 0.9mm wire (0.035").

Feed rollers / drive rollers

Feed rollers or drive rollers are used to feed the wire mechanically along the length of the welding gun. So when you pull the trigger on the mig welding gun and feed rollers become energized and start rolling forward. These are what control your welding wire feed speed. If they spin faster the wire will feed faster if they spin slower wire will feed slower. There will be an adjustment knob on the front of the welding machines for this control.

Feed rollers are designed to be used for certain types of welding wire. Your normal mild steel solid wire needs to be used with a V groove roller. Aluminium wire needs to be used with U-shaped rollers. This is because the U-shaped roller offers more surface area grip and traction to help feed the softer wire. Flux cored welding wires also should use a U-shaped feed roller. But most people seem to use a knurled feed roller for your gasless and flux cored wires. If you use a knurled wire feed roller on flux cored wire it will slowly over time bit by bit eat away at the surface of the welding wire, and these small pieces will eventually go down into the liner. This will cause added friction and could lead to welding wire feed problems.

Go to the mig welder page.