TM 10-3530-207-14
Table 3-1.
Operator Troubleshooting - continued.
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
CLOTHING SEWING MACHINE
10.
BOBBIN THREAD BREAKS.
Step 1. Check that bobbin case is threaded correctly and installed correctly.
Thread and install bobbin case correctly (paras. 2-11d through 2-11g).
Step 2. Check bobbin to see that it is not so full of thread as to keep it from revolving freely in the
bobbin case.
Remove excess thread until rounds of thread are even with the rim of the bobbin (para. 2-
11e).
Step 3. Check that rounds of thread on bobbin are not lapped over one another and check that
rounds of thread are evenly wound across the bobbin (no - ridges or valleys in therounds).
Use a correctly wound bobbin or remove thread and rewind bobbin correctly with proper
thread (para. 2-lle).
NOTE
In steps 2 and 3 above, the problem could be misadjustment of bobbin winder.
Step 4. Check that bobbin case tension is not too tight.
Adjust bobbin case for correct tension (para. 2-11j).
Step 5. Check that bobbin case is not sticky with oil and lint.
If bobbin case is sticky, notify next higher level of maintenance.
Step 6. Check that rough, sharp, or burred edges on oscillating
shuttle, bobbin, and bobbin case.
If defects are found, notify next higher level of maintenance.
Step 7. Check that thread being used is not damp, old, or dried out.
Discard damp, old, or dried out thread. Rewind bobbin with fresh, dry, smooth thread of the
correct weight (para. 2-11e).
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