19
(2) Adjusting the lower thread tension
Like in figure 25, turning the tension adjustment nut
①
of the hook clockwise makes the lower thread tension
stronger and counterclockwise makes it weaker.
(3) Adjusting the tension of thread take up lever
spring
A. Adjusting the thread take up stroke
As in figure 26, loosen the stopper fastening screw
①
, and turn the thread take up lever
’
s spring stopper
②
clockwise to make the stroke smaller and counter
clockwise to make it bigger. The thread take up
stroke is normally 5~10mm.
B. Adjusting the thread take up tension
As in figure 26, loosen the screw
③
of the thread
tension control assembly, and insert the driver into
the groove
④
of the thread tension control assembly.
Turn clockwise to make the spring tension stronger
and counter clockwise to make it weaker. The thread
take up spring tension is normally 30~70g.
[Figure 25]
strong
Strong
weak
Weak
Small
Large
(4) Adjusting the thread release stroke. (for automatic trimming type)
If the upper thread falls out from the needle hole after trimming, check whether the plate
①
opens while the trimming is
in action. For the adjustment of plate opening level, put the solenoid
②
in action, and adjust by moving solenoid collar
③
back and forth to make the opening of the thread tension adjusting plate
①
0.8 mm. Also, when the thread release
solenoid is not in action, check whether the plates are closely adhered to each other. (See figure 27)
[Caution]
If the plates do not open enough during trimming action even when the assembling is correctly done, check whether or
not the upper thread length adjustment volume, which is at the front of the control box, is low.
[Figure 27]
[Figure 26]
about 0.8 mm
