Rewind the bobbin. Remove lint from beneath the flat tension spring on the bobbin case. Needle too thick for fabric; tension too high.
Press the foot pedal to wind the thread. Once full, slide the spindle back, cut the thread, and retighten the inner clutch knob. Inserting the Bobbin and Case victoria 537 manual
The Victoria 537 usually features a built-in bobbin winder located on the top right or front of the machine. Rewind the bobbin