Straight answers to the questions people ask when choosing a front-end consumable kit for a large-body TIG torch.
What is a gas lens and why do some kits include one?
A gas lens replaces the standard collet body. Instead of side holes that make the shielding gas swirl, it uses fine mesh screens to straighten the flow into a smoother, steadier column. That gives better protection to the weld pool and the hot tungsten.
It also lets you extend the tungsten further from the cup, which helps you see the joint and reach awkward corners. Lens kits are popular for stainless steel and other work where gas cover matters most. A standard collet body is fine for non-critical work and short tungsten extension.
How do I choose the right cup size?
A larger cup gives a wider, longer stretch of smooth gas flow, so it protects the weld better. A smaller cup helps you get into tight spots, but it pushes the gas out faster and can make it turbulent. As a general rule, use the largest and longest cup that the joint allows.
The cup must match the collet body or gas lens in your torch, because the threads and seals differ between designs. Check the torch manual for the cup sizes it accepts, and keep a small and a large cup to hand.
How far can the tungsten stick out of the cup?
With a standard collet body, keep the tungsten extension short, within the cup, otherwise the gas cover breaks down. With a gas lens you can usually extend it further, which is the main reason to use one.
How far is safe depends on the cup, the lens, the gas flow and the joint, so treat any figure as a starting point and follow the torch maker's guidance. If you see porosity or a discoloured weld, shorten the extension, check for draughts and check the gas flow before changing anything else.
Does the order I assemble the torch front end matter?
A common order is to fit the collet body or gas lens into the torch head first, then the cup, then slide in the tungsten and collet from the front, and finally fit the back cap, which clamps the tungsten. Guides differ slightly on when the back cap goes in, so follow the order in your torch manual.
Tighten parts by hand without forcing them, because over-tightening can damage threads and ceramic cups, and a loosely seated collet body can let air into the gas stream. Look over the insulators and seals whenever you open the torch, and replace any that are cracked or worn.
Which type of tungsten should I use, and is thoriated still needed?
The choice depends on the metal and on whether you weld with AC or DC. Ceriated and lanthanated types are widely accepted as alternatives to thoriated, particularly on DC, and lanthanated is often used as a general-purpose option.
Thoriated tungsten is slightly radioactive, so where it is not essential for the weld it is sensible to consider the alternatives. Colour codes help you identify the type, but check the packaging, because some mixed or newer types are not covered by the standard colours.
Is there any safety concern with the tungsten I use?
The main concern is with thoriated tungsten, and it is the grinding dust, not the arc. Grinding exposes the most thoria, so use a dedicated grinder with local dust extraction, wear suitable respiratory protection, keep the area clean and wash your hands before breaks.
Store thoriated electrodes in a closed, labelled box. Ceriated and lanthanated electrodes carry a lower hazard, though sensible dust control still applies to all tungsten grinding. Base your controls on your own risk assessment and the maker's instructions.