Bernina 900 electronic - Lower Thread Tension Check; Regularity and Tension Check; Regulation of Lower Thread Tension

Check
of lower
thread
tension
Metrosene:
mercerised
thread 100X3
(Ne 60/3) or
Daming
thread:
mercerised
thread 120/2
(Ne 70/2)
or
mercerised
thread 100/2
(Ne 60/2)
Regularity check
Check
whether
the
thread
can be
moved
Bobbin
case
spring
screw
must be
on top
to-and-fro perfectly
freely as it leaves
be-
low the bobbin case
spring.
The
bobbin case spring
screw must
be at
the
top
without
fail.
Fig
58
>
rS_
i~
Tension
check
The
shuttle must be
used as a weight
to
check
the
tension.
As illustrated,
the shuttle
with bobbin case
is suspended
from the lower
thread
to
Fig.
58
check the
tension,
When
the hand is lightly
jerked, the shuttle
and bobbin
case should move
slowly
downwards.
They must stop
moving immediately,
how-
ever, when the
movement of the
hand
ceases.
Regulation
Regulation
is performed
on
the bobbin
ca-
se spring
screw with
the aid of a small
screwdriver,
turning to
left = weaker
turning
to
right
=
stronger
Upper thread tension
Adapt
the upper
thread
tension
to that
of
the lower
thread set as described
above.
138
Fig, 59