someone’s’ asked me to model something for a lathe to make… any ideas on the format? They don’t seem to know anything about it. I thought here might be a good place to start but im about to hit google 
stl probably, make sure to hit it with the stl check utility to be certain it is waterproof
Well the modelling shouldnt be too hard considering it will be on a lathe in the real world hence use a lathe modifier, 
Max is not an option I would use for creating engineering models with, if you have Rhino (possible you can d/l a trial) it would be a breeze, as it intergrates with CAM software. Anyway if u r confined to MAX I think you’re only option is a stl format which is biased towards the sterolithographic process, but it still may work.
If you’re not going to use Rhino then maybe model in Max using nurbs and then export it out as iges. Most CAM apps would prefer to have nurbs than polys I think.