17
MODEL 520
MECHANICAL ADJUSTMENT
NEEDLE THREAD TENSION
The standard tension should be 75 to 90 grams when the tension dial is set at "4", measured
with a #50 white polyester thread being pulled at approximately 110 mm/sec.
If the tension is outside the standard range, adjust as follows:
ADJUSTMENT:
1. Set the thread tension dial to "4" and check the thread tension.
2. Remove the front cover (see page 7).
3. Pull the adjusting plate spring (A) away from the lead screw (B) and adjust by turning the
lead screw (B).
If the tension is strong , turn the lead screw in direction “C”.
If the tension is weak, turn the lead screw in direction “D”.
4. Attach the front cover.
Thread (polyester sewing
thread (#50 white))
Pull the thread at a speed of approx. 110 mm/
sec. In the direction of arrow.
Adjusting plate spring (A)
D
C
Lead screw (B)