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Backcap Long (with O-Ring).
Answers on cups, collet bodies, back caps and screens for a small TIG torch with a gas saver set-up.
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.
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.