Upper Thread Keeps Breaking: Find the Snag, Needle or Excess Drag Before You Change Parts
When the upper thread keeps breaking, the useful first question is where the thread is failing, not how far to turn the tension dial. Repeated snapping can come from an obstructed spool path, incorrect threading, excessive upper tension, a damaged or unsuitable needle, a poor needle-and-thread match, or a rough user-visible surface that is abrading