Thread Tension; Main Thread Tension; Adjusting The Sub Tension Timing; Adjusting The Thread Presser Tension Opening Amount - Brother BM-917B Instruction Manual

10. THREAD TENSION

10. THREAD TENSION
Turn off the power switch before carrying out this operation.
The machine may operate if the pedal is pressed by mistake, which could result in injury.
* The motor will keep turning even after the power is switched off as a result of the motor's inertia. Wait until the
motor stops fully before starting work.
When turning the machine pulley by hand, turn the pulley until the needle is at the final position after one cycle.
If the needle is at a point midway through the cycle when the power is turned on, the machine will immediately start
operating, which could result in injury.

10-1. Main thread tension

Becomes
weaker

10-2. Adjusting the sub tension timing

45mm
10mm

10-3. Adjusting the thread presser tension opening amount

Opening amount
becomes larger
Loosen
0.5-0.8mm
15
Becomes
stronger
Reference line
Slow looseing
Quick looseing
Sub tension
Loosen
Opening amount
becomes smaller
CAUTION
The main thread tension is adjusted by turning the tension nut
(1).
1995M
Pass the thread through only the sub tension, and then
!
1996M
while gently pulling the thread, check the timing at which
the pressure of the tension discs (1) starts to loosen.
Turn the machine pulley by hand to raise the needle bar (2)
!
until the reference line is aligned with the top edge of
needle bar bush U (3) (needle bar height 45 mm), and
adjust the timing so that the tension discs (1) start to
loosen at this point.
1. Loosen the set screw (4), and then turn the sub tension
stud (5) to adjust the timing.
2. Tighten the set screw (4).
1997M
Adjust so that the tension disc presser (1) opens by 0.5-0.8
mm when the sewing machine starts (when the machine
pulley is turned by hand).
1. Loosen the nut (2), and then turn the thread presser
tension stud (3) to adjust the opening amount.
2. Tighten the nut (2).
1998M
BM-917B, 917C