14
6.2 Negligent sewing, pulling of the
material.
6.3 Needle too thin for thick material.
6.4 Needle incorrectly mounted.
6.5 Throat plate loosened.
6.6 Upper thread tension too high.
7.1 Feeder too low.
7.2 Feeder used.
7.3 Feeder teeth fouled or blunt.
7.4 Insufficient presser foot pressure.
8.1 Incised spring on bobbin case,
lower thread insufficiently braked.
8.2 Lower thread not threaded under
bobbin case spring.
8.3 Lower thread retained under the
bobbin case spring.
8.4 Unequal setting of upper and lower
thread tension.
8.5 Machine feeds too soon.
9.1 Tensioning disks incised by upper
thread.
9.2 Thread does not pass around hook
or is retained by the bobbin case.
9.3 Upper thread not threaded between
the tensioning disks.
9.4 Lower thread retained between the
tensioning disks.
9.5 Unequal setting of upper and lower
thread tension.
10.1 Lower thread wastes retained in
hook.
11.1 Excessive tension of auxiliary ten-
sioner.
11.2 Cam time setting too quick.
11.3 Machine stops before upper dead
center.
11.4 Electromagnet loosening main
tensioner is out of function.
11.5 Incorrect upper thread unwinding.
12.1 Lower thread end drawn into bob-
bin case.
12.2 Excessive winding up speed.
12.3 Excessive lower thread tension.
12.4 Burr on the covering hook sheet.
13.1 Incorrectly set up (little) pressure
of fixed knife.
13.2 Blunt fixed or trimming knife.
Let material pass freely.
Replace needle according to par. 6.3,
part A.
Mount correctly needle according to par.
6.3, part A.
Mount throat plate according to par. 5,
part C.
Set tension according to par. 6.4, part A.
Set the feeder height according par. 3,
part C.
Replace.
Clean or replace feeder.
Increase pressure according to par. 6.8,
part A.
Replace spring.
Rethread thread according to par. 6.5,
part A.
Clean.
Set thread tension according to par. 6.4
and 6.5, part A.
Set feeding according to par. 3; 6; 7,
part C.
Replace disks and set upper thread ten-
sion according to par. 6.4 and 6.5, part A.
Clean hook and set up bobbin case.
Thread correctly the thread according to
par. 6.1, part A.
Clean thread tensioner and set it accord-
ing. 6.4, part A.
Set correctly according to par. 6.4,
part A.
Move hand wheel in spite of conside-
rable resistance in both senses until the
threads in the hook get cut up. After hav-
ing removed them, let run the machine
unthreaded a while and then lubricate the
hook with 2-3 drops of oil recommended
in the par. 7, part A.
Reduce tension according to par. 6.1,
part A.
Delay according to par. 21, part C.
Set according 27, part C.
Find out the cause and repair.
Repair.
Increase lower thread winding up tension
according to par. 6.2, part A.
Maintain maximum number of revolu-
tions 140/min.
Reduce according to par. 6.5, part A.
Polish up.
Set according to par. 26, part C.
Replace or sharpen.
7. Difficult and uneven machine feed-
ing.
8. Incorrect stitch locking. Threads
locked on the top side of sewn ma-
terial.
9. Incorrect stitch locking. Threads
locked on the bottom side of sewn
material.
10. Hook blocked.
11. Little reserve of upper thread, ma-
chine does not start sewing, upper
thread leaves needle eye at the start
of next sewing.
12. Little reserve of lower thread, ma-
chine does not start sewing.
13. Thread ends untrimming or insuf-
ficiently trimming.
