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Answers on cups, collet bodies, back caps and screens for a small TIG torch with a gas saver set-up.
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.
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.
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.
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.