Hello Lin,
The 348 was always one of my favourite machines, set the top tension on 4 or 5, make sure that you adjust the botton tension so you can just pull the thread through with slight resistence, remember to makew sure the presser foot is up when you thread the machine, remember that most Singer machines will only sew well with perfect mercerized thread no thicker than a number 40, some do not even sew well with that.
Ken
ken, December 2010
