All of my vintage machines are actually set at 3, when I was introduced to sewing machines both at home and at school I was told by my mother and teacher not to change that so I didn't. That being said there were not the different weights of thread then as there are now. Even now I can't say I make changes to the settings on most of my machines, the computerized one's came with a setting of 4 that's where I leave it unless my thread weight changes dramatically.