Owner's Manual

LK3-B438E Mark II
23
Turn off the power switch before removing and replacing the bobbin case, otherwise the machine
may operate if the foot switch is depressed by mistake and serious injury could result.
q
30mm
CAUTION
7-5. Replacing the bobbin case and threading the thread
Pull the shuttle race cover q toward
you to open it.
Insert a new bobbin into the bobbin
case, and then pass the thread
through the slot w and pull it out
from the thread hole e. Check that
the bobbin turns in the direction of
the arrow when the thread is pulled
at this time.
Pass the thread through the lever
thread hole r, and then pull out ap-
proximately 30 mm of thread.
7-6 . Thread tension reference guide
w
e
r
7. CORRECT USE
Weaker
Stronger
Weaker
Stronger
w
q
7-6-1 . Lower thread tension
Adjust the thread tension to the weakest possible ten-
sion by turning the thread tension nut q until the bob-
bin case will not drop by its own weight while the
thread end coming out of the bobbin case is held.
7-6-2 . Upper thread tension
Turn the tension nut q(main tension) to adjust the
tension as appropriate for the material being sewn.
Furthermore, turn the thread nut w(sub-tension) to ad-
just the remaining length of upper thread to 35 - 40
mm when the thread take-up lever is not used.
weaker stronger
q
Upper thread tension (N)
Lower thread tension (N)
Thread take-up spring height
(mm)
#60 or equivalent
0.7 - 1.3
0.3 - 0.4
6 - 8
Thread
Pre-tension (N)
Needle
0.4 - 0.6
0.1 - 0.3
TQ × 1#12
Thread take-up spring tension
(mm)