I found a great video I wanted to share on TIG welding techniques for tubular stainless steel header fabrication. It's a professionally done video with some great, very clear welding puddle shots, and at the end the completed welds look fantastic.
highlights:
3:38 - recommended accessories: flexible TIG torch cable, large diameter gas lens & cup
(that big cup, which looks like a #12, takes 30 cfh gas flow! Looks like he is using a WP-17 torch. 1/16" tungsten)
4:27 - backpurging equipment and technique
6:50 - tack welding without filler rod
7:10 - butt welding of .065" tubing without pulse
(he states with 45 amps and a .045" filler rod)
7:45 - butt welding with low speed pulsing
(he states 90 amps peak, 10% background, 30% pulse duty cycle, and it looks like about ~1.5 pulse per second)
8:54 - fillet welding of .065" tubing to 3/8" flange