Answers on cups, collet bodies, back caps and screens for a small TIG torch with a gas saver set-up.
Why is grinding a thoriated tungsten a safety concern, and what are the alternatives?
Thoria is slightly radioactive. Welding with the electrode is a very small hazard, but grinding is the main concern because it exposes more thoria and releases fine dust that may be harmful if breathed in. Controls include a dedicated grinding wheel with local dust extraction, a simple filter mask, closed storage and careful clean-up of the dust, for example sealing it in a bag.
Ceriated or lanthanated tungsten are generally acceptable replacements, particularly for DC welding, and zirconiated tungsten is often used for AC welding. Follow your risk assessment and the torch maker's instructions, and ask your safety adviser about storage and disposal rules.
What should I do before changing cups, collets or screens on a TIG torch?
Switch the welder off or isolate it first. A torch maker's manual warns that the electrode and work circuit are electrically live whenever the output is on, so never handle torch parts with the power live. Parts around the cup and collet get hot in use, so allow a cooling period before working on the torch and use gloves if anything is still warm.
Lay the old parts out in order, check the new ones against the torch series shown in the manual, and look for cracks, chips or stripped threads before you refit. Keep the work area clean so that grit does not get into the gas path. If you are unsure of the order of parts, follow the maker's parts diagram.
What does a gas saver body do for tungsten stick-out on a small torch?
A standard collet body passes the shielding gas out through a few small side holes, which can leave the flow turbulent. A gas saver or gas lens body adds fine mesh screens that smooth the argon into a steadier column. A torch maker's troubleshooting guide lists changing to gas saver or gas lens parts as the remedy for excessive turbulence in the gas stream, and lists a larger cup and reduced stick-out where stick-out is excessive.
A steadier column usually lets you work with a longer stick-out for access and a clearer view, though with a very short stick-out you may notice little difference. Keep within the maker's recommended stick-out. If the tungsten oxidises as it cools, the same guide suggests increasing the post-flow time.
How do I tell a worn collet or collet body, and why must they match the tungsten?
The collet grips the tungsten and passes current to it, and the collet body holds the collet and directs the gas. Torch parts lists give collets and collet bodies for each tungsten diameter, so both must match your tungsten size and your torch series. A loose or worn collet lets the tungsten move, which can give poor contact and a wandering arc.
A maker's troubleshooting guide notes that ordinary split collets can twist or jam and suggests a wedge-style collet where collet life is short, and replacing the collet where there is excessive heating inside the torch. Replace any collet that is twisted, scored, discoloured or no longer grips firmly, and check the manual if the symptom persists.
Can I mix cups and collet bodies from different torch series or types?
Not safely. A maker's parts list for this type of torch shows standard parts and gas saver parts as separate sets. The gas saver set has its own collet body and heat shield, and there is a further large-diameter set with its own matching body and heat shield. Cups, bodies and screens are designed to work together, so a cup that does not match its body may not seat, seal or direct the gas properly.
Before ordering, confirm the torch series from the torch head or manual, then match the collet body, collet, heat shield, cup and back cap to that series, the set type and your tungsten size. If your old parts carry markings, use them to identify the type, and ask for help choosing if you are unsure.
Should I choose a glass or an alumina cup?
Glass (borosilicate) cups are clear, so you can see the weld pool and the tungsten, which many welders like in corners. Supplier catalogues describe glass cups as breaking more easily than alumina, which is opaque but tougher and the more common type. A welding training site says glass suits corners but is not well suited to walking the cup, and the cup maker's data should be checked for any current or temperature limit.
A torch maker's troubleshooting guide lists cup shattering in use as a short parts-life problem and suggests changing the cup size or type, or the tungsten position. Replace any cup that is cracked or chipped, and handle glass gently.