Answers to common questions about light-duty, air-cooled TIG torches and the small-head consumables that go with them.
What is the difference between a gas lens and a standard collet body?
A standard collet body releases shielding gas through a few small holes, which can leave the flow slightly turbulent. A gas lens holds a diffuser and mesh screens that smooth the gas into an even, laminar stream, so you usually get better coverage and a cleaner weld.
A gas lens also lets the tungsten stick out further, which helps you see the joint and reach into tight corners. The standard collet body is perfectly adequate for general work. Whichever you choose, match its size to your tungsten diameter and make sure it is made for your torch head.
How do I choose a gas cup size and the right argon flow?
Cups are numbered by their internal diameter in sixteenths of an inch, so each step up adds about 1.6 mm. Smaller cups give better visibility and access; larger cups give wider gas cover and allow more tungsten stick-out.
A common rule of thumb is to set the flow in litres per minute close to the cup number, and a gas lens often needs less than a standard collet body for the same cup. Too much flow causes turbulence that can pull air into the weld, so more is not better. Follow the guidance for your torch and consumables, and adjust for drafts and the material.
What does a duty cycle rating mean on a torch?
Duty cycle is the number of minutes out of a 10-minute period that equipment can run at its rated output without overheating; some makers use a 5-minute period instead. For example, 60% at a given current means about 6 minutes of welding and 4 minutes of cooling.
The rating only applies at the current stated beside it, and lower currents generally allow longer arc-on time. A torch rated below the current you actually set can overheat, so check the rating on the torch or its data plate and the maker's conditions for it, such as gas, AC or DC, and cable length.
Which tungsten electrode type and size should I use in a small air-cooled torch?
Pick the tungsten diameter to suit the current you will actually weld at, and the type to suit AC or DC. For AC work, mainly aluminium, zirconiated tungsten is the usual choice. For DC, lanthanated or ceriated electrodes are accepted alternatives to the older thoriated type and need no special precautions.
A smaller air-cooled torch head takes smaller electrode diameters, so check the maximum size on the torch data plate. Collets, collet bodies and gas lenses should be sized to match the electrode (for example, a 2.4 mm electrode needs a 2.4 mm collet).
Are there risks when grinding tungsten electrodes?
Yes. Thoriated electrodes are slightly radioactive. The external hazard is negligible, but grinding creates fine dust that is potentially radioactive, and the dust is the main concern.
Use a grinder reserved for tungsten with local dust extraction, wear a suitable dust mask and eye protection, and avoid breathing or spreading the dust. Lanthanated and ceriated electrodes are non-radioactive alternatives, so it is worth asking whether you need thoriated at all. Follow the electrode maker's instructions and your own risk assessment.
What are the fume and eye hazards when TIG welding?
The HSE says that welding fume carries both short-term and long-term health risks, and that ozone in particular can be produced when TIG welding stainless steel and aluminium, causing throat dryness, coughing or chest tightness. Use extraction or other controls, as set out by your risk assessment.
Ultraviolet light from the arc can cause arc eye, an injury to the front of the eye that usually becomes painful and red a few hours later. The skin can also be burned. Wear appropriate welding eye protection and cover exposed skin, and screen the area so others are not exposed.