Practical answers on the wearing parts of a heavier-duty air-cooled TIG torch and how to match, fit and look after them.
What does a large-diameter parts set change, and what else must I fit with it?
A large-diameter set uses a wider cup with a larger diffuser screen so the gas covers a bigger area around the weld. Maker parts charts list it as its own matched set, with its own cup, collet body, collet and heat shield, separate from the standard and gas saver sets.
Because the parts are made to work together, do not fit a large-diameter cup onto a standard collet body or heat shield unless the manual says it is allowed. The wider cup is bulkier, so check you can still see and reach the joint. Match the parts to the torch series on the data plate and to your tungsten diameter.
How do I know a gas lens screen is worn or clogged?
A gas lens collet body has a fine mesh screen that smooths the gas flow. Heat or spatter can clog, discolour or warp the mesh, which disturbs the flow and weakens shielding. Check the screen regularly and replace a damaged or blocked gas lens or screen; many designs cannot be cleaned or have the screen removed, so follow the torch manual.
Signs include discoloured welds, uneven gas coverage or more porosity than usual with the same settings. Switch the gas off and let the torch cool before removing it, and do not poke the screen with sharp tools, as that can distort the mesh.
How do gas saver parts work, and how much difference do they make to gas use?
Gas saver parts use a wide cup with a diffuser screen so the gas leaves at a lower speed and a smoother flow. The maker's troubleshooting guide lists a change to gas saver or gas lens parts as a way to deal with turbulence and poor shielding.
Makers quote lower gas use with these parts, but the figure depends on what it is compared against and no independent test was found, so treat any percentage as a guide only. In practice the result depends on the cup, the joint, your flow setting and drafts. Use the maker's chart as a starting point and confirm coverage with a test weld.
My arc is erratic after changing parts. What should I check?
The maker's troubleshooting guide lists several causes of an erratic arc: an arc that is too long, current too low for the tungsten size, a contaminated electrode, a narrow joint, contaminated shielding gas and dirty or oily metal.
For contaminated gas, the guide says the most common cause is moisture or air in the gas stream, so use welding-grade gas and look for leaks at the hoses, back cap, O-rings and fittings. If the tungsten is contaminated, remove the affected end and prepare it again. Also check the collet is the right size and seated properly.
How do I avoid tungsten inclusions in the weld?
Tungsten inclusions mean pieces of electrode have ended up in the weld. The maker's troubleshooting guide lists causes including excessive current for the electrode size, touching the pool or filler rod with the tungsten, and excessive electrode extension.
Parts and set-up matter too. Poor shielding or drafts are a listed cause, and the fixes include increasing gas flow, shielding the arc from wind or using gas lens parts. Keep the tungsten extension within what the manual recommends for your cup, make sure the collet grips the electrode firmly, and use a high-frequency or lift arc start rather than scratch starts.
Why do torch heads and collets wear out quickly?
The maker's troubleshooting guide gives short torch head life as a result of working beyond the rated capacity and of bending rigid heads. It advises staying within the rated capacity, using a water-cooled model where you need more, and not bending rigid torches.
Short collet life is another listed problem, usually from the ordinary slotted collet twisting or jamming, with a wedge-style collet suggested instead. Heat is the common factor, so check the rating on the data plate and the manual against the current you actually weld at. Heads, collets and cups are wear parts and should be replaced when worn.