Bernina KL. 940 Service Manual page 41

1
me great majority of casesfaults can be attributed to improper handling of the
achine. Should other causes be suspected, however, the machine must be examined as
to whether:
a) The needle is properly fitted. The long groove must always be at the front from where
the machine is threaded.
b) The right needle size is being used, needle No. 7 0 for fine darning work and No. 80 or
90 for other sewing work.
C)
The hook is lubricated with a few drops of oil.
d) There are no remnants of material between the thread tensioning discs.
e) There are no remnants of material stuck underneath the bobbin case tensioning spring.
fl
The machine can be turned easily with the handwheel.
2. Thread breakage at the upper thread can be caused by the following
a) Use of poor quality, badly polished needles. Needles should always be boughtfrom the
BERNINA dealer.
3. Lower thread breakage
Can be caused by the following:
a) The lower thread tension is too great.
b) The lower thread is badly wound.
b) Needle wronglyfitted. Long groove must be at front.
c) The needle is blunt or bent.
d) The rebtiocrship of thread thickness to needle is not correct.
e) The
tension
of the upper thread is too great.
f) Poor yam
o r yarn with knots. Yarn has dried during long storage. It should never be
stored in heated, rooms.
g) The needle plate hole has been struck by the needle and must be re-polished.
h) The
hook
tip
is damaged.
c) The bobbin is crushed and jammed in the case.
d) The needle plate hole has been struck by the needle and must be re-polished.