Fronius MTG320i & MTB320i Parts FAQs
Straight answers on choosing, fitting and looking after the wearing parts of a gas-cooled MIG torch from one maker's range.
How do I make sure I order the right part for my torch?
Start with the torch itself. Note the type designation on the torch body or handle and look it up in the maker's operating instructions or parts list, which show every wearing part for that torch. Then note your wire diameter and wire type, and the shape and thread of the old part.
Parts are tailored to a particular torch and process, so a part that looks the same may not seat or conduct properly. If you are unsure, compare the old part with the parts list, or ask the maker or our team before you order.
Which parts wear out first, and what does a worn part look like?
The contact tip, gas nozzle, insulating parts, nozzle fittings and spatter guard are the usual wearing parts, because they face heat, spatter and the constant rubbing of the wire.
The maker's instructions describe the signs to look for. On a contact tip, the wire entry and exit holes wear oval or the tip is heavily covered in spatter. On a gas nozzle, the edges are burned off, notched or clogged with spatter. Check the wearing parts every time you start work and replace any that are damaged rather than waiting for the weld to suffer.
What are contact tips made from, and does the material matter?
Yes, it can. Plain copper tips have good electrical conductivity and are the usual choice for general work on steel, stainless steel and aluminium. Harder copper alloys, such as copper-chromium-zirconium, resist heat and wear better, so they suit heavy use, long arc-on times and abrasive wires such as some cored or uncoppered wires, though their conductivity is slightly lower.
The right choice depends on your wire material, your welding current and how long you weld at a time, so follow the torch maker's recommendation. Some tips are made specifically for aluminium wire. Whatever the material, the bore must match your wire size.
How do I choose between gas nozzle shapes and sizes?
A nozzle trades gas coverage against access. A straight (cylindrical) nozzle gives the best gas flow and is common at higher currents, but it limits access. Conical nozzles spread gas well and keep a good view of the weld. Bottle-shaped or tapered nozzles reach into tight joints but give tighter coverage and gather spatter faster.
In general, use the largest bore that still lets you reach the joint, because a small nozzle clogs sooner and can starve the weld of gas. Heavy-duty versions are made for longer life in demanding use. Nozzles are made for a particular torch, so check the fit.