GMAW with a 5/8" nozzle typically runs between 30-45 CFH for manual operations... Maybe slightly higher for high speed automation.

GTAW cup/nozzles are sized with a number..  The number represents 1/16" inside diameter.  Typical might be 15 CFH for a #4 up to about 25-30 for a #10

External factors such as air movement, travel speed, gun angle, diffuser type will have an effect.

Any welding textbook produced in the last 25 years has this information.

Here is a quick online reference for GTAW
http://www.ckworldwide.com/technical_specs.pdf

Good GMAW basics here
http://www.thefabricator.com/article/arcwelding/preparing-for-gmaw-back-to-basics-all-about-setup

Also....check the data sheets produced by your welding electrode mfg....a lot of times they have suggested cfh values for using their product listed on these documents.

I don't own this standard but it may be helpful.

http://pubs.aws.org/p/156/c55c55m2003-recommended-practices-for-gas-tungsten-arc-welding

as a general rule we start around 20cfh for TIG then adjust down until it gives us issues (on a test piece) then backoff. True number is usually around 15 CFH, any lower and the savings from the gas is eaten up by possible defects.   Same thing for GMAW.

Hi Jarhead,

Not sure if you're just using aluminum, but this handbook has been very helpful.

http://pubs.aws.org/p/271/phb-8-the-everyday-pocket-handbook-for-gas-metal-arc-welding-gmaw-of-aluminum

Tori