Hello Ann,
The 348 was one of my favourite machines, make sure first of all that the machine is threaded properly with the presser foot up, make sure the needle is in the correct way round, remember that these models are very fussy on the type of thread, use 40 or 50 sylko or Guttermans if you can, top tension should be about 4 or 5, you should only just be able to pull the bottom thread through with slight resistence, if it is too tight slacken the screw on the bobbin case about a quarter of a turn anti clockwise at a time and test.
ken
drivewithken
July 2009
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