Bernina 531 Manual - Page 29

The threading of the bottom thread when sewing buttonholes automatically t.- •,- I Lever (for actuating the locking catch) 4. joh,,, 44 • An increased tension of the bottom thread produces best results when sewing buttonholes automatically. To get this higher bottom thread tension without changing the lower tension itself, which is correct for normal sewing, a hole was drilled through the finger of the bobbin case through which the bottom thread has to be threaded (see adjoining illustration). 0 Stitch-length lever 530-2 Fig.27 a Through this measure the bottom thread tension is slightly increased and the hook a will take leas thread from the bobbin which is correct for good buttonhole sewing. For normal sewing the bobbin case is threaded as explained in the instruction booklet on page 17. 52 Fla. 28