which TIG welder

Not a big fan of aluminum spool guns(squirt gun for surface welds that will crack out when stressed!) that's what they use for mass production docks,pontoon boats and anything else the want to turn out quick!. You really need a machine that has at the minimum AC Hi Frequency.I will use argon for light aluminum with a red (pointed 1 1/2 times diameter) non thoriated tungsten to keep my arc wander down to a minimum and for heavier casts or flanges I'll use a helium argon mix or (straight helium and avoid any preheat!) I welded with green/ pure thoriated tungsten for years with the big old ball on the end but have since become been a big fan of the red lately as I like to control my arc as to were I want it! Oh yes my machine, an old Miller Syncrowave 250 but you can get by with a lot less machine than that.