LGS3 150G Mig Torch Parts FAQs
Consumables and wear parts for a light-duty, gas-cooled MIG torch: contact tips, nozzles and wire liners, and how to choose and look after them.
How do I know when a contact tip is worn?
The main sign is the bore. A new tip has a round hole; a worn tip has a hole that has become oval or egg-shaped, or noticeably larger than the wire. Wire friction wears it, and heat speeds that up. A tip with wire fused into it after a burnback should be replaced too.
Symptoms include an unstable arc, poor starts, wire that sticks or feeds unevenly and more spatter. Spatter or blackening on the outside is not by itself a reason to change a tip, so inspect the bore rather than changing tips by habit. Compare it against a new tip if you are unsure.
Why does a loose contact tip cause problems, and what causes burnback?
A tip that is not seated firmly in its holder makes a poor electrical joint. That raises resistance and heat, wears the tip faster and can discolour the threads. Tighten consumables so they seat firmly, but do not over-tighten, and let the torch cool before changing parts.
Burnback is when the wire fuses to the tip. It is more likely if the tip is too close to the work, if the tip bore is worn or the wrong size, or if wire feed is poor. Check the tip, the liner, the drive rolls and your technique before blaming a single part. The maker's manual gives the correct tip position for your torch.
Do I need a different contact tip for aluminium wire?
Often, yes. Aluminium wire is soft and expands with heat, so a tip for aluminium usually has a slightly larger bore or a design made for aluminium, to stop the wire binding. Using a tip sized for steel on aluminium wire can cause sticking and burnback.
Check the tip marking against the wire size and follow the torch and wire maker's recommendation. Aluminium also needs a suitable liner and the correct drive rolls, so treat the tip as one part of a set-up. Keep tips for aluminium separate from those used on other wires, so that you do not mix them up. Details depend on the equipment, so check your manual.
What are the differences between nozzle shapes?
Conical nozzles give good gas coverage with a clear view of the weld, and suit much manual welding. Cylindrical (straight) nozzles have a large straight bore and are commonly used at higher currents, but give less access in tight spots. Bottle-shaped and tapered nozzles have a narrower tip for better access, but gas coverage is tighter and more easily disturbed by draughts.
As a guide, use the largest bore that still lets you reach the joint. Choose the shape that fits your torch and the joints you weld most often. Check the nozzle matches your tip and diffuser.