I've been shopping around for a decent surface plate or alignment table for a surface jig I have. What sort of tolerances are generally necessary/acceptable on a table for frame building? I have a friend who has a fab shop and we've been talking about building something interesting ourselves but we're not sure of the tolerances we need to be within. The various surface plates I've looked at have pretty incredible tolerances, but then I hear stories about alignment tables at various factories having tolerances with +/- multiple millimeters. That's far from the thousandths that most surface plates seem to be (granite or otherwise).
I recall e-richie saying something about his measurements being only reproducible on his alignment table, which was also the story at UBI (same model of table I believe) and in a lot of cases you couldn't even duplicate them consistently if you sat there all day flipping the frame around. When all was said on my first frame I was somewhere within 1-1.5mm of runout when I put it on the table. That was averaged out over a few times of taking it on and off the table and that's assuming the table was accurate. After fitting up the bike it seems a ton straighter than anything else I've ever owned.
Anyway, just curious what the opinion here is. And yes, buying a chunk of granite would be easier, but where's the fun in that? :)