21
GUIDE TO TIG WELDING
Before starting any welding activity ensure that you have suitable eye protection and
protective clothing. Also take the necessary steps to protect any persons within the welding
area.
TIG torch body and components
The torch body holds the various welding
consumables in place as shown and is covered by
a either a rigid phenolic or rubberised covering.
Collet body
The collet body screws into the
torch body. It is replaceable
and is changed to accommodate the different
sizes tungstens and their respective collets.
Collets
The welding electrode (tungsten) is held in the torch by the collet. The collet is
usually made of copper or a copper alloy. The collet
’
s grip on the electrode is
secured when the torch back cap is tightened in place. Good electrical contact between the collet and
tungsten electrode is essential for good welding current transfer.
Gas lens body
A gas lens is a device that can be used in place of the normal collet body. It screws into
the torch body and is used to reduce turbulence in the flow of shield gas and produce
a stiff column of undisturbed flow of shielding gas. A gas lens will allow the welder to
move the nozzle further away from the joint allowing increased visibility of the arc.
A much larger diameter nozzle can be used which will produce a large blanket of shielding gas. This can be
very useful in welding material like titanium. The gas lens will also enable the welder to reach joints with
limited access such as inside corners.
Ceramic cups
Gas cups are made of various types of heat resistant materials in different shapes,
diameters and lengths. The cups are either screwed onto the collet body or gas
lens body or in some cases pushed in place. Cups can be made of ceramic, metal,
metal
-
jacketed ceramic, glass or other materials. The ceramic type is quite easily
broken so take care when putting the torch down.
Gas cups must be large enough to provide adequate shielding gas coverage to the
weld pool and surrounding area. A cup of a given size will allow only a given
amount of gas to flow before the gas flow becomes disturbed due to the speed
of flow. Should this condition exist the size of cup should be increased to allow the flow speed to reduce
and once again establish an effective regular shield.
Back cap
The back cap screws into the rear on the torch head and applies pressure to the back end of the collet
which in turn forces up against the collet body, the resulting pressure holds the tungsten in place to
ensure it does not move during the welding process.
Back caps are made from a rigid phenolic material and generally come in 3 sizes, short, medium and long.
