TIG O’Rings:

TIG torch o’rings, are normally found in two places:

  • On the back cap, where it screws into the TIG gun body (to provide a shielding gas seal).
  • On a glass gas nozzle (heat resistant o’rings x 2). Used for holding a glass gas cup in place, when there is no thread present.
TIG Back Cap, Gas Cup & Gas Nozzle O’Rings


TIG Torch O’Ring Properties & Temperature Range:

The Viton type o’ring appears to be the most durable type, due to its ability to resist heat and its wear resistance…

TIG Torch O’Ring Properties & Temperature Range
O’Ring Type Notes Temp’ ℃
Nitrile General purpose. -50 to 120
Silicone Liable to tear. -50 to 200
Viton Stronger chemical resistance. -25 to 210
The Viton o’ring appears to be the most durable…

TIG Torch O’Ring Sizes:

TIG Consumables – Back Cap O’Rings

Table showing TIG Torch Back Cap O’Ring Sizes:

TIG Welding Torch – Back Cap O’Ring Sizes
Group O’Ring
Back Cap O’Rings
mm Inches
Air WP-17 A 012 1.78 x 9.25 ID
(12.81 OD)
1/16 x 3/8 ID
(1/2 OD)
Air WP-26
Water WP-18
Air WP-9 B 008 1.78 x 4.47 ID
(8.03 OD)
1/16 x 3/16 ID
(5/16 OD)
Water WP-20

This is only a guide, please refer to the torch manufacturers data sheets…
1 Manufacturers may use a different code, sometimes replacing the first two letters with their own combination.


  • Measure the o’rings fitted to your TIG torch before purchasing, as there could be slight differences between torch manufacturers.
  • As the table shows (in the link above), there are two different sizes between Groups A & B.
  • The O’Ring code relates to the BS or AS standard. i.e. The reference might be BS-012, or AS-012.
  • The colour of an O’Ring doesn’t mean it’s a particular type, as they can be manufactured in any colour you want. Therefore check the material specifications.

TIG Glass Gas Cup & Gas Nozzle O’Rings Sizes:

TIG Consumables – Glass Gas Cup, O’Rings, Gas Nozzle & Insulator

TIG Glass Gas Cup & Gas Nozzle O’Rings Sizes:

TIG Glass Gas Cup & Gas Nozzle O’Ring Sizes
O’Ring Code Gas Cup & Gas Nozzle O’Rings
mm Inches
110 2.62 x 9.19 ID (14.43 OD) 0.103 x 0.362 ID (0.568 OD)
This is only a guide, please refer to the manufacturers data sheets.

Buying O’Rings:

When ordering O’Rings, you can use the BS or AS reference number, (e.g. BS-012, or AS-012). Or, you can just use the measurements…

  • ID = Internal Diameter.
  • OD = Outside Diameter.
  • W = Width (the O’Ring thickness, or ‘wire’ size).
To get the Outside Diameter:

Use the… Internal Diameter (ID) & Width (W):

ID + (W + W)    =   OD

To get the Inside Diameter:

Use the… Outside Diameter (OD) & Width (W):

OD – (W + W)    =   ID

To get the Width (O’Ring Thickness, or ‘Wire’ Size):

Use the… Outside Diameter (OD) & Internal Diameter (ID):

(ODID) / 2    =    W


  • Beware when using measurements. The size is often defined by either the Internal Diameter (ID), or the Outside Diameter (OD) and the o-ring thickness (‘wire’ size). Sometimes suppliers will offer both the ID and OD measurements for you to check (but not always). So check you’re using the correct measurements (ID or OD?).
  • A manufacturer may use different colours to indicate the different types of o-ring. However, the colour doesn’t always indicate the type of o-ring it is? O-rings can be manufactured in any colour you want, therefore always check the type, don’t rely on visual ‘colour’ identification.
  • Don’t forget, o-rings are often fitted to provide a seal. Therefore the Internal Diameter (ID) may need to be ‘snug’ fit, and the Outside Diameter (OD) a ‘proud’ fit.

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