I TIG welded a bike frame up and it turns out my jig was not terribly accurate. I set up my frame on a granite table, and clamped the bottom bracket to the top of the table. measuring from the granite table up to two points on the head tube, my head tube is off by roughly .037"[just under 1MM](measured at both ends of a 190MM HT). my seat tube is off by .077"[ just under 2 mm](measured close to the BB and right around the TT and ST junction. this is on a 58 cm frame.
my questions are, what do you measure when you build a frame, and what are your acceptable tolerances?