Fabrication process for noncircular vacuum seal

An improved process for fabricating a sealing flange assembly useful for oval and other noncircular access ports in high vacuum equipment is disclosed. The process is applicable to sealing flange assemblies of the type which include relatively hard metallic flange members having opposed, mating surfaces at least a portion of which are chamfered to define a V-shaped notch therebetween and a relatively soft metallic sealing member disposed in the notch under compression against the chamfered surfaces. The process relates specifically to the machining of the chamfered sealing surfaces by a milling process which utilizes a specially ground end mill and selected depths of cut to provide a more or less grooved sealing surface profile essentially devoid of tool chatter marks and metal folds which represent nonsealable surface defects. The as-milled chamfered sealing surfaces are much coarser (32 mu inch finish) than those produced by grinding (8 mu inch finish) but nevertheless are effective in maintaining a vacuum tight condition in the assembly at a pressure level of 8x10-8 torr whereas the ground, finer finish sealing surfaces are not.