Plain answers on which spare parts wear on a small air-cooled TIG torch, how the part families differ and how to fit and look after them.
What are the different families of parts for this type of torch, and can I mix them?
TIG torch parts are normally grouped into families: standard, gas lens, gas saver, large diameter and short (stubby). Each family has its own cup, collet body, heat shield and sometimes back cap, and the maker's parts chart lists them as matched sets.
As a rule, keep to one family at a time. A cup made for one family may not seal against the heat shield or collet body of another. The collets themselves are usually common across families and are chosen by tungsten diameter, although short and wedge versions exist, so check the chart. Check the torch series on the data plate or in the manual, then pick parts from a single column of the parts chart.
Which parts wear out first, and how do I tell they are worn?
The parts that take the heat and handling wear first: collets, cups, O-rings and the back cap. A worn or deformed collet can cause poor arc starts and an unstable arc. A cracked cup or back cap, or a flattened or dried-out O-ring, can let shielding gas leak or draw air in, which shows up as porosity or discoloured welds.
A damaged heat shield or insulator can allow arcing or overheating. Look over these parts each time you change the tungsten, and replace anything cracked, distorted, burnt or loose rather than waiting for a failed weld.
Why does a standard collet jam or twist, and is a wedge collet worth fitting?
An ordinary collet has a slot cut along its end. Under heat and repeated tightening that slotted style can split, twist or jam, which shortens its life. The maker's troubleshooting guide suggests changing to a wedge style when collet life is short, and the maker's parts guide says wedge collets can improve arc starting, stability and control.
A wedge collet has no slot and grips by an angled end pressing into the collet body. Claims that it lasts many times longer come from makers and sellers, and independent tests are not widely published, so treat them as a guide only. Always match the collet to the tungsten diameter and make sure it is made for your torch series.
Why does my gas cup crack or shatter, and what can I change?
Cups take radiant heat, thermal shock and knocks. The maker's troubleshooting guide lists cup cracking or shattering in use as a short-parts-life problem and suggests changing the cup size or type, or changing the tungsten position, rather than just replacing like for like.
Cup material matters. Alumina is the general-purpose, impact-resistant choice, while lava-type ceramic cups are generally used where a lot of heat is reflected back, such as in confined joints. Never scrape spatter off with a tool that could chip the cup, and replace any cup that is cracked or chipped, as a damaged cup can let gas leak and spoil shielding.
Should I choose a glass cup or an alumina (ceramic) cup?
Glass cups are chosen when you need to see the arc and joint, for example inside corners or awkward positions. They are generally regarded as more fragile than ceramic and can break if dropped or knocked.
Alumina cups are opaque but are the usual general-purpose, impact-resistant choice. Lava-type ceramic cups are generally used where reflected heat is high, but are less impact resistant. The cup material itself does not save gas; any saving comes from the gas lens or gas saver design behind it. Whichever you choose, it must match the collet body, heat shield and torch series.
What does the heat shield do, and when should I replace it?
The heat shield (sometimes called the insulator or cup gasket) sits between the torch head and the cup. It helps protect the head from radiant heat, helps seal the gas path so gas goes to the cup, and provides electrical insulation between the head and the cup.
Let the torch cool before removing it, and check how it fits in your manual or parts chart. Replace it if it is cracked, burnt, loose or no longer seals. Heat shields are shaped to suit the cup and torch, so use the shield from the same parts family as your cup.