I got one of these just a while ago . . I wish I knew how to link you, but I know I put singer 248 in my question line. someone directed me to the singer website, where you can download the manual for free. I was having trouble properly threading the bobbin. the manual helped, but I didn't get tension smoothed before I hurt my hand (dishwashing accident). Now I cannot mess with it at all. I did learn that the dial on the top is the presser foot pressure. Mine is missing the slide plate, and I wonder if that is contributing to its (my?) problem!!
Good luck with yours! I will be curious (and learning vicariously thru you!!)
Lara