Duerkopp Adler 558 Operating Instructions Manual page 41

Underthread tension
The underthread tension is set by turning the knurled nut 3 on the hook bracket.
Tension increase
Tension decrease
Thread pull-on spring for the underthread
The thread pull-on spring 1 influences the pull-on of the underthread through its stopper
width and pre-tension and thus the form and beading of the buttonhole.
Setting the stopper width:
Setting the pre-tension:
Gimps
The upper and lower gimp should be pulled easily and uniformly from the guide hole in
the needle plate and the gimp guider.
For a faultless appearance of the buttonhole a braking or clamping of the gimp on its
way to the sewing station is to be avoided.
= turn to the right
= turn to the left
Loosen screw 5 and turn the angle 4.
Loosen screw 6 and turn angle 2.
43