api500010,000 PSI - Type 6BX API 6A - Table E.4 . Nominal size of Flange: Maximum Bore: Outside Diameter of Flange: Max. ChamferAPI has specified weld necks for many 6BX flanges, and not done so for many others, but API has provided the basis for determining the dimensions of a 6BX integral flange that the manufacturer may attach to a