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Aircrew Survival Equipmentman 1 & C - Aviation theories and other practices | Next
Troubleshooting Chart-Continued |
Table 4-4.—Troubleshooting Chart—Continued
2. Feeding Problems—Continued
Trouble
Probable Cause
Remedy
F E ED
Feed-driving crank pinch screw
Recenter feed and tighten pinch screw.
F A I L U RE
loose
Feed-driving eccentric out of spline
Reset.
Feed dogs set too high
Reset.
Set at negative feed
Set for stitching.
F E E D I NG
Feed lifting cam out of spline
Reset in spline.
B A C K W A R DS
Feed-driving eccentric out of spline
Reset in spline.
Presser-lifting eccentric out of
Time eccentric.
time
Timing collar our of spline
Reset in spline and retime machine.
S T I T C H ES
Insufficient presser foot pressure
Add spring pressure.
NOT IN
L I NE
Feed dogs too low
Set height to one full tooth.
M A T E R I AL
Presser foot pressure too great
Reduce pressure.
DAMAGED BY
S C U F F I N G
Feed dogs too high
Set one full tooth or less.
3. Miscellaneous Problems
T H R E A D
Operating machine without ma-
Unthread when running without fabric.
J A M M I NG
terial
Failure to hold free ends of thread
Maintain pressure.
for first stitches.
Bobbin-case opener incorrectly set
Readjust opener.
Needle thread not between tension
Thread discs.
discs
Hook too high
Lower hook.
Turning balance wheel backwards
Remove jam.
with needle threaded
Thread, dirt, lint under bobbin
Remove case; clean and replace.
case
4-15
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