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Practical answers on the torch consumables, wire feed parts and holder spares used with a multi-process MIG welder, and how to match them to your machine.
The bore is made only slightly larger than the wire so that the wire makes good electrical contact as it passes through. Running a smaller wire through an oversize tip limits current transfer and causes constant micro-arcing inside the tip, which wears it out early. An oversize bore also hurts current pick-up, so tips should be replaced when wear is excessive.So check the wire diameter on the spool and use a tip marked for that diameter, and the thread and length your torch takes. Look at the markings on the tip and in the torch manual.
It matters a lot. A tip that is loose, or not sitting flat on its holder, gives a poor electrical connection, which makes it overheat and wear quickly. The tip should sit flat on the tip holder with the threads in full contact, tightened with a suitable tool.As a rule, screw it in by hand and then snug it with the correct tip tool; over-tightening can damage the tip or the holder. Do this with the torch cold and the machine isolated, and make sure the tip, holder and diffuser are all clean and fully seated before you start welding.
The liner guides the wire from the feeder to the contact tip and must suit both the wire material and its diameter. Hard wires such as steel and stainless generally use a spirally wound steel liner, while soft wires such as aluminium and copper generally use a PTFE liner. A liner with too large a bore gives the wire too little support, so it can fold and tangle in the feeder.So choose by wire type first, then by the diameter range printed on the liner, and make sure it is long enough for your torch. Do not rely on colour codes alone, as these can differ between makers. Check the torch manual for the liner type it takes.
Cut the liner with a sharp side cutter for a clean edge and remove any burrs, because burrs shave the wire and cause feeding trouble. A common reason for a liner wearing out early is cutting it too short. The liner should seat flush against the contact tip, with slight pressure when the tip is screwed in.Keep the cable as straight as possible while fitting, and compare the new length against the old one and the torch manual. A pull test helps: if you cannot pull the wire through by hand with the feed rolls released, the wire or liner needs attention. Isolate the machine first.