In my experience with chatter on a lathe. I have noticed that it’s mostly caused from poorly adjusted end shake (pre-load) in the main spindle bearings. Or from a flexing tool bit or something else in that area. Not to say jib adjustment is out of the question but I have not seen too much of that. A crack in the casting on a cross slide once. Of course this depends on the size of lathe, lathe design, material being cut, type of tool profile and a gamut of other excuses…Dave
If you do not have chatter but a funny tool cut pattern? Then that could be from harmonics within the power train being transmitted to the work finish. Like motor noise, whining gears, belt(s) too tight, etc.