Gas lens, cup, diffuser, O-ring and cover spares for a large-cup TIG torch, and how to match and look after them.
What should I do before changing consumables on a hot torch?
Switch off and isolate the machine, close the gas supply and let the torch cool completely before changing cups, lenses or O-rings. TIG torch heads get very hot in use, and the manual for your torch may call for gloves, so follow its instructions.
Avoid levering with tools that could chip or crack a ceramic or glass cup. Fit the parts in the order the manual shows and tighten them only as far as it says, because over-tightening can damage threads and cups, and unsuitable parts or incorrect assembly can damage the torch. Follow the torch maker's instructions and your risk assessment for isolating and handling the equipment.
How do I identify the right replacement parts for my torch?
Start with the torch series or the code stamped on the torch head or lead, then use the manual's parts list or exploded diagram to find each part. A torch maker's manual warns that unsuitable consumables or incorrect installation can damage the torch and impair results, so use the parts the maker specifies.
Consumables for different torch families often look similar but do not interchange, and cups, gas lenses and O-rings must match each other as well as the torch. Check your tungsten diameter, the cup number on the old cup and whether you use a standard or large-diameter lens. If a part has no markings, measure its thread and bore. Do not mix series unless the maker says they fit.
How often should the torch itself be inspected and serviced?
There is no universal interval, so follow the manual for your torch and your risk assessment. Torch heads, cables and connections are exposed to high temperatures, so makers generally call for regular checks, and more often in heavy or demanding use. Some manuals leave periodic maintenance to a qualified person.
Between services, look over the cups, gas lens, O-rings, insulator, threads and cable each time you change consumables. Before any maintenance, isolate the electrical supply, close the gas supply and let the torch cool, because the head becomes very hot in use. Use only the consumable parts the torch maker specifies.
What does a gas lens do compared with a standard collet body?
A standard collet body releases shielding gas through a few small side holes, which can leave the flow uneven and turbulent. A gas lens passes the gas through layers of fine mesh, so it leaves the cup as a smoother, more even column. That usually gives better coverage of the weld pool and lets the tungsten extend further than the inside diameter of a standard cup.
The difference is often small with a very short stick-out and grows as the stick-out increases. A gas lens does not replace a sensible cup size and gas flow, and it needs a cup that matches the lens, so check the torch manual for which parts go together.
How do I choose the right cup size?
Cups are normally numbered in sixteenths of an inch across the bore, so a larger number means a wider cup and a wider gas shield. Larger diameters generally give a longer, steadier gas flow, while smaller ones suit tight spaces but raise gas velocity. With a standard collet body, keep the tungsten extension within the cup bore. A gas lens lets you go further.
A bigger cup is not always better. It can block your view and access into the joint, and it uses more gas to fill. Make sure the cup fits your torch style and gas lens, as parts for different torch series often do not swap.
Should I use a glass cup or an alumina cup?
Glass cups, usually borosilicate, are clear, so you can see the arc and the joint. That helps in corners and on fiddly work. Alumina (ceramic) cups are opaque but are generally regarded as the tougher, more durable choice, and many welders prefer them with larger cups and longer stick-outs, where the visibility advantage matters less.
Glass breaks more easily than ceramic if it is dropped, knocked or exposed to intense heat, so inspect it before use and replace it if it is chipped or cracked. Cups of any material are brittle and are often the first part to break if a torch is dropped. Follow the torch manual for which cups suit your torch and gas lens.