SINGER 331K4 - Manual (Page 9)

REGULATION
BOBBIN THREAD TENSION:
For average sewing, tension on bobbin thread should
be very light.
To regulate tension on bobbin thread, remove the
bobbin case and turn screw in tension spring, as in­
structed in Fig. 20.
^When tension on bobbin thread has been correctly
adjusted for ordinary stitching, the required stitch
can usually be obtained thereafter to suit the work in
process by varying the tension on needle thread
only.
Fig. 20. Regulating Bobbin Thread Tension
NEEDLE THREAD TENSION:
To avoid accumulating excessive tension on needle
thread, first obtain correct tension on bobbin thread, as
instructed above.
Regulate needle thread tension only when
presser foot is down (since needle thread tension is
automatically released when presser foot is raised).
Tension on needle thread should be just enough to
set stitch correctly in material.
Having lowered presser foot, turn thumb nut at the
front of tension discs either over toward right or left, as
required. See instructions in Fig. 21.
PRESSURE OF PRESSER FOOT
ON THE MATERIAL:
Fig. 21. Regulating Needle Thread Tension
The correct presser foot pressure helps feed the
work efficiently. You can regulate the amount of pres­
sure exerted by the presser foot on the material by
means of the thumb screw, as shown in Fig. 22.
The pressure on the material should be as light as
possible, while sufficient to insure correct feeding.
To increase the pressure turn the thumb screw down­
ward.
To reduce the pressure turn this screw upward.
The pressure is correct when the work moves steadily
and smoothly without stalling.
MORE PRESSURE
Fig. 22. Regulating the Pressure on the Material