Brother S-7220D Instruction Manual page 77

Problem
Upper and lower threads
are breaking.
Incorrect thread trimming
Incorrect thread trimming
(Upper thread is not being
trimmed.)
(Lower thread is not being
trimmed.)
Broken needle
Possible cause
• Is the needle tip bent? Is the needle tip blunt?
If the needle tip is bent or blunt, replace the needle.
• Is the needle properly installed?
If it is incorrect, install the needle correctly.
• Is the machine properly threaded?
If it is incorrect, thread the thread correctly.
• Is the rotary hook sufficiently lubricated?
If the oil gauge is down to the lower reference line in
the oil gauge window, add more oil.
• Is the upper or lower thread tension too strong or too
weak?
Adjust the upper thread or lower thread tension.
• Is the upper thread loose because the thread take-up
spring stroke is too small?
Adjust the position of the thread take-up spring.
• Is the rotary hook, feed dog or other part damaged?
If the thread path is damaged, smooth it with
sandpaper or similar. Alternatively, replace the
1
damaged part.
• Is the thread path damaged?
If the thread path is damaged, smooth it with
sandpaper. Alternatively, replace the damaged part.
• Is the fixed knife or movable knife damaged or worn?
Replace the fixed knife or the movable knife.
• Is the needle properly installed?
If it is incorrect, install the needle correctly.
• Is the fixed knife or movable knife blunt?
Replace the fixed knife or the movable knife.
• Is the material being pushed or pulled with excessive
force during sewing?
• Is the needle properly installed?
If it is incorrect, install the needle correctly.
• Is the needle tip bent? Is the needle tip broken, or is
the needle hole blocked?
Replace the needle.
• Is the needle and rotary hook timing correct?
Adjust the height of the needle bar.
Adjust the clearance between the needle and the tip
1
of the rotary hook.
• Is the needle and feed mechanism timing correct?
Adjust to the standard timing.
Page
See Checking the
condition of the needle and
upper thread on page 50.
See Lubrication on page 7.
1
1
See Replacing the fixed
knife and movable knife on
1
page 53.
See Replacing the fixed
knife and movable knife on
page 53.
See Replacing the fixed
knife and movable knife on
page 53.
See Adjusting the height of
the needle bar on page 56.
1
See Adjusting the needle
and rotary hook timing on
page 57.
See Adjusting the needle
and feed timing on
1
page 60.
67