MIG Guns and Consumables

What it is

A MIG (GMAW) gun connects to the wire feeder. Wire runs through the liner inside the cable, gas flows alongside it, and current passes to the wire through the contact tip. The front-end consumables are:

• Contact tip: copper tip with a bore sized to the wire. It transfers current.
• Gas diffuser (retaining head): holds the tip and spreads gas evenly.
• Nozzle: directs gas around the arc and protects the tip.
• Liner: guides the wire from the feeder to the tip.

Guns are covered by IEC 60974-7.

How to identify

Gun and consumable families are matched by the gun maker and model. Tips are stamped with the wire size and often the thread or style. Nozzles are sold by bore size and recess or stick-out. Liners are sold by wire size range and length. Many guns can be converted between consumable families with a new neck and diffuser.

Consumables and wear signs

Liner types

• Steel (coiled) liners for steel and stainless wire.
• Nylon or PTFE (plastic) liners for aluminum and some soft wires. They reduce friction and avoid shaving the wire.
• Liners must be trimmed to the length the maker gives. A short liner leaves a gap where wire kinks; a long one bunches up.

Key points

• Match tip size to wire diameter. See the contact tip and wire size matching chart and the matching MIG gun consumables sheet.
• Tip recess (how far the tip sits inside the nozzle) changes with process. Spray transfer often uses a recessed tip; short circuit often uses flush or stick-out.
• Gun amperage ratings depend on shielding gas and duty cycle. Mixed gas ratings are lower than CO2 ratings for the same gun.
• Blow out the liner when changing wire spools.

Common mistakes

• Using a steel liner with aluminum wire.
• Mixing consumables from different gun families.
• Running a worn, keyholed tip until the arc wanders.
• Cutting a liner too short.

Governing standards: IEC 60974-7 (torches); AWS A5 filler metal specifications for wire size tolerances; gun maker's consumable charts.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.