Brother LK3-B448E 40,46, Troubleshooting, Poor seam finish on reverse side of material

18. Troubleshooting

Problem

Cause Check

Remedy	Page
Sharpen or replace the

Upper thread is not trimmed.

Thread jamming

Poor seam finish on reverse side of material.

Incorrect thread tightness

Button breaks.

Fixed knife is blunt.

Movable knife does not pick up the thread.

The movable knife does not pick up the thread because of skipped stitches at the sewing end.

Movable knife position is incorrect.

Sub-tension is too weak.

Thread takeup spring tension and height are incorrect.

Incorrect needle and rotary hook timing

Shuttle race thread guide is not separating the threads.

Shuttle race thread guide is not separating the threads.

Upper thread is not properly tight.

Uneven upper thread length

Upper thread tension is too weak.

Lower thread tension is too weak.

Thread takeup spring tension and height are incorrect.

Needle is striking the button.

Fixed knife blade

Shuttle race thread guide position

Needle bar lift amount

Skipped stitches at sewing end

Movable knife position

Sub-tension

Thread takeup spring tension and height

Needle bar lift amount

Shuttle race thread guide position

Shuttle race thread guide position

Upper thread tension

Upper thread length

Upper thread tension

Lower thread tension

Thread takeup spring tension and height

Needle down setting

fixed knife.
Adjust the position of	43
the shuttle race thread
guide.
Adjust the needle bar lift	41
amount.
Refer to "Skipped
stitches occur".
Adjust the position of	45
the movable knife.
Turn the sub-tension	27
nut to adjust the
tension.
Adjust the tension and	30
height of the thread
takeup spring.
Adjust the needle bar	41
lift amount.
Adjust the position of	43
the shuttle race thread
guide.
Adjust the position of	43
the shuttle race thread
tension.
Adjust the upper	29
thread tension.
Adjust the sub-tension.	27
Adjust the upper	29
thread tension.
Adjust the lower thread	29
tension.
Adjust the tension and	30
height of the thread
takeup spring.
Adjust so that the	40,46
needle drops into the
hole of the button.

70

LK3-B448E MARKII/BA-16