46
17. Adjustment of bobbin thread tension
Requirement:
The force required for pulling cotton thread 50/2 or synthetic fiber thread 100/3 off the bobbin must be
approximately 25 - 30 g.
Check:
● When a threaded bobbin case hangs on its thread, it must not slide downwards by its own weight.
● With a sharp upward movement of the hand, the thread must run off gradually (fig. 46).
● There must not be any thread waste under the tension spring.
● The tension spring must rest evenly and parallel on the bobbin case.
Adjustment:
Loosen the knurled screw a little and turn it in again until a resistance is felt when the thread is pulled off.
Check:
● Carry out as described under "Check"
Note:
● Once the bobbin thread tension has been set correctly, tension adjustments must be made only to the
needle thread tension.
18. Adjustment of needle thread tension
Requirement:
Within the adjusting range from 3 to 5, the interlacing of the needle thread and the bobbin thread (cotton
thread 50/2 or synthetic fiber thread 100/3) must take place approximately in the middle of the fabric in
straight and zigzag stitch setting (fig. 47 and fig. 50).
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