Adjustments; Needle Bar Height; Loop Spreader; Point Where Needle And Looper Meet - Brother CB3-B917 Service Manual

5.ADJUSTMENT
5. ADJUSTMENT
Assembly and adjustment of the sewing machine
should only be carried out by a qualified
technician.
Turn off the power switch at the following times,
otherwise the machine may operate if the pedal
is depressed 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 carrying out inspection, adjustment and
maintenance
• When replacing consumable parts such as the
loopers and knife.
If the power switch needs to be left on when
carrying out some adjustment, be extremely
careful to observe all safety precautions.

5-1.Needle bar height

Needle bar lowest position
Needle bar
With the needle bar at the lowest position, align the reference
line of the needle bar with the lower edge of the needle bar
metal.

5-3.Point where needle and looper meet

TQx1
Needle
TQx7
bar
324s
Raise the needle bar from the lowest position until it is aligned
with the needle bar metal. Adjust the tip of the looper so that it
is at the center of the needle by using the Looper setting
shaft.
* Set the delta cam lightly against the looper spreader groove
cam.

5-5.Needle guard

Needle
guard
329s
The clearance between the needle and the needle guard
should be 0.1 – 0.2 mm.
35
TQx1
TQx7
307s
501s
Looper
spreader
groove
looper
cam
Looper setting
shaft
0.1 – 0.2 mm
CB3-B916A/B917A
CAUTION
Be sure to wear protective goggles and gloves
when handling the lubricating oil and grease, so
that they do not get into your eyes or onto your
skin, otherwise inflammation can result.
Furthermore, do not drink the oil or eat the grease
under any circumstances, as they can cause
vomiting and diarrhoea.
Keep the oil out of the reach of children.
Use only the proper replacement parts as
specified by Brother.
If any safety devices have been removed, be
absolutely sure to re-install them to their original
positions and check that they operate correctly
before using the machine.
Any problems in machine operation which result
from unauthorized modifications to the machine
will not be covered by the warranty.

5-2.Loop spreader

Loop spreader
319s
Looper spreader groove cam
Move the needle to its lowest position by rotating the pulley.
When the loop spreader has been advanced to its closest
point to you by turning the looper spreader groove cam, adjust
the clearance between the needle to 0.3 – 0.5 mm by moving
the loop spreader groove cam backward and forward.

5-4.Clearance between needle bar and looper

0.03 – 0.08 mm
326s
When the tip of the looper is aligned with the center of the
needle, the clearance between the looper and the needle
should be 0.03 – 0.08 mm.

5-6.Fixed knife

Approx. 2 mm
The distance between the blade edge of the fixed knife and
the center of the needle should be approximately 2 mm.
Loop spreader
Needle
320s
0.3 – 0.5 mm
Screw
looper
Fixed knife
331s