Dürkopp Adler 52 i Series Operating Instructions Manual page 47

Operation
Operating Instructions 52Xi, 52Xi-75 - 00.0 - 10/2021
Setting the tension spring (2)
1. Remove the bobbin case (5) from the machine and insert a
full-wound bobbin (4).
2. Do a complete threading according to picture (A).
3. Regulate the spring (2) pressure with a screw (3) so that the
thread tension is in balance with the case and bobbin weight.
 When hung down on the thread end (1) the case is dropping
slowly with its own weight.
Setting of bobbin brake spring at the thread trimming (6)
Important
Bobbin braking should be as small as possible because it causes
difference of tensions of full and empty bobbin and subsequently
of thread interlacing in the stitch (defective look of the seam).
1. Regulate the bobbin braking with a screw (7) and watch the
bobbin unwinding after the thread trimming: remove the
case (5) from the machine, grip it so that the bobbin can not
turn and pull out the thread end (8).
 At a correct adjustment, approx. 10 mm of thread will be
pulled out of the case.
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