Shroud Size

[Will_Davis]

Ok, Lets stop the funny comments straight away!. I'm 6' 3" so when I snuff it I will need 6' 6" of shroud wrap!!

Seriously though my TIG has been supplied with 3 different shrouds: Nos: 5,6,7

These numbers seem to be unrelated to actual diameter ( but thats not a problem )

How do I know which size to use? The tutorial mentions "For general purpose work on steel a number 7 shroud is a good compromise. A smaller number 4 shroud would be more suitable for fillet welds, and larger shrouds might be used for aluminium. As a rule the larger the shroud the better the gas coverage."

I am concentrating on butt welds in 1.2mm or thinner SS sheet.

I assume that the bigger the shroud the more gas is needed ( More gass = More Money per mm of weld )

As an overall request is there a one-off "covers-all" table of Tig specs:

Material / Weld Orientation / Thickness / Tungsten dia / Filler Rod dia / Current / Shroud dia / Gas Flow / 'Owt else I've forgotten!

Cheers

Will

 

[hotrodder]

They're sized in 1/16ths of an inch i.e. a #6 is ~ 3/8" bore. As per the tutorial bigger = better gas coverage, you don't need higher flow rates when going from a #4 to a #7 but with say a fillet weld the larger cup requires more stick out to reach the weld. More stick out = possibly and sometimes lesser shield quality than a small cup with less stick out. Turning the gas flow up to compensate for more stick out can actually make things worse by creating a sorta venturi effect and drawing air in

Personally i use a gas lens set up (several threads if you search the TIG forum) which cope with lots of stick out better instead of swapping to a smaller cup. Probably 90% of the time it's a #7, gas flow varied from 4 or 5 lpm upto 7 or 8 depending on amperage (higher amps = bigger weldpool), joint type and amount of stick out.

As an overall request is there a one-off "covers-all" table of Tig specs:

Material / Weld Orientation / Thickness / Tungsten dia / Filler Rod dia / Current / Shroud dia / Gas Flow / 'Owt else I've forgotten!

Probably several and i promise you they won't agree with each other everywhere... some set cup size by amperage, tungsten size and material and then set gas flow but don't consider weld joint access for example. Ask 6 welders and you'll get at least 6 answers. About the only thing they're likely to agree on is that arc length is very important and (probably) use the largest ceramic/cup that's practical