Originally Posted by Psimet2001
"Perfect 90 degree"???
If you mean, "how do you keep the shell faces parallel to each other?" Then yes you would have a point....doing it with a file will not achieve perfectly parallel faces, but in good hands the file will be able to put the faces close enough (in parallel) for any noticeable binding to be eliminated.
Actually, 90 degrees to the plane of the spindle. The shell faces may be parallel, but not at right angles to the spindle. But agreed that a file wouldn't do the job without a large degree of patience and checking. That is, if the facing was ever needed in the first place (which is rarely if ever is if a cartridge BB is to be used).