Parts of a MIG Gun – Labeled Gun and Welder Diagram

All 15 parts on the diagram

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The gun 7

Nozzle The tube round the front end of the gun. It directs the shielding gas evenly onto the weld area.
Contact tip A small tube, normally copper, that the wire slides through. It passes the welding current to the wire and aims the wire at the weld.
Gas diffuser A piece inside the nozzle, behind the contact tip. The shielding gas passes through it.
Welding wire The wire is the electrode. It is fed through the gun all the time and melts into the weld.
Torch handle The part of the gun held in the hand. The trigger is on it.
Trigger It is the control switch. Pressing it starts the wire feed, the electric power and the flow of shielding gas.
Liner A tube inside the cable. It guards and guides the wire on its way to the contact tip.

The machine 8

Gas cylinder The tank that holds the shielding gas. The gas keeps air away from the weld.
Regulator It lowers the gas pressure from the cylinder and controls its flow.
Gas hose It carries the shielding gas from the regulator to the machine. Then on to the gun.
Wire spool A reel of welding wire. The wire is pulled off it as it is used.
Drive rollers Two rollers that grip the wire between them. They push it toward the gun.
Wire feeder Drives the wire through the cable and on to the contact tip.
Power source The cabinet that supplies the welding current. Most MIG welding uses a power supply that holds a constant voltage.
Ground clamp A clamp on a cable from the machine. It is fastened to the work.

How this list was compiled: Every name checked on 2026-09-30 and kept only where at least two of these use it. (1) Wikipedia, Gas metal arc welding, https://en.wikipedia.org/wiki/Gas_metal_arc_welding : the equipment is a welding gun, a wire feed unit, a welding power supply, a welding electrode wire and a shielding gas supply; the gun has a control switch or trigger, a contact tip, a gas nozzle, an electrode conduit and liner and a gas hose; its cutaway names the torch handle and the shielding gas diffuser. (2) US Army, TM 9-237, Operator's Manual for Welding Theory and Application, full text at https://archive.org/details/micro_IA41152616_0592 : MIG torch nomenclature (contact tube, nozzle, torch handle, trigger, the spool of wire electrode), the argon gas hose, regulators to reduce pressure and control the flow of gas from cylinders, the work clamp, the welding power supply. (3) A welder maker's operator's manual, https://archive.org/details/manualzilla-id-7307992 : contact tip, nozzle, gun liner, trigger, drive roller, spool of wire, ground clamp, power source. (4) A second maker's manual, https://archive.org/details/manualzilla-id-5920770 : contact tips, gas diffusers, drive rollers, wire liner, torch trigger, spool holder, ground clamp, gas hose and regulator, power source. (5) A third maker's manual, https://archive.org/details/manualzilla-id-6890509 : wire spool, wire feed mechanism, liner, gas hose, regulator on the gas bottle, power source. (6) A gun maker's product guide, https://archive.org/details/manualsbase-id-664577 : gas diffuser, nozzle, contact tip, wire feeders. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's tool, nothing traced. Licence: own work

How it works

In MIG welding a wire is fed through a gun and melts into the weld, while a shielding gas keeps air away. The first view shows the gun; the second shows the machine.

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The gun

Pressing the trigger on the torch handle starts the wire, the power and the gas. The welding wire runs through the liner inside the cable and out through the contact tip, which passes the current to it. The gas comes through the gas diffuser, and the nozzle directs it onto the weld.

The machine

The power source is the cabinet. Inside, the wire feeder pulls wire off the wire spool and pushes it to the gun with its drive rollers. Shielding gas comes from the gas cylinder through the regulator and the gas hose. The ground clamp is fastened to the work.

MIG stands for metal inert gas. The full name of the process is gas metal arc welding.

Questions and answers

What are the parts of a MIG gun?

At the front, the nozzle with the contact tip and the gas diffuser inside it. Behind them, the torch handle and the trigger. Inside the cable, the liner that guides the welding wire.

What are the parts of a MIG welder?

A power source, a wire feeder with its drive rollers, a spool of wire, a gun on a cable, a ground clamp, and a gas supply: the cylinder, its regulator and the gas hose.

What does the contact tip do?

It passes the welding current to the wire as the wire slides through it, and it aims the wire at the weld. It is normally made of copper.

What is the liner in a MIG gun?

A tube inside the cable between the machine and the gun. The wire runs through it, and it guards and guides the wire so that the feed is not interrupted.