.625 = 5/8 = #10. Sometimes I modify cups to make something that fits into a tight spot.
purge setup depends on what I’m welding and how big it is. Longer exhaust stuff I use a draw through inflatable purge bag. that reduces the gas waste as you’re not filling the entire exhaust every time you go to weld a new joint. Short stuff I just put stoppers in the ends and purge the whole tube.
ss headers built on jigs with built in purge ports. Ti stuff always goes in the chambers which fill 100% with shielding gas, unless it’s too big then I get creative. Stuff is too expensive to mess up.
I’ll use SFB on things that I can’t purge easy, like large open tanks and boxes or structures, or on repair jobs where you need to lift contaminates away from the backside of the weld(like cast stainless exhuast manifolds and crap like that. But on a turbo manifold you MUST remove the ceramic it leaves behind because it will break off and end up causing turbine damage. It’s nearly impossibly to do on long tube or twisty runner turbo headers so DO NOT use it for such a thing, only short runner/log style cast manifolds where you can see all the weld joint on the backside and can blast it away with media(I use steel shot)
that’s about it, nothing fancy. no real need to get uber fancy with it just as long as you get the atmosphere away form the weld. I know guys and shops that just stuff rags in the tube ends and stick a piece of plastic airbrake tubing in the end and fill it up. Works and get’s the job done just fine.