TM 10-3530-207-14
2-12. OPERATING PROCEDURES FOR DARNING SEWING MACHINE - continued.
i. Adjusting Tension on Bobbin and Needle Threads.
(1) Proper tension locks the bobbin and needle threads in the center of the material. If needle thread
tension is too tight, or if bobbin tension is too loose, the needle thread will pull to the upper surface of
the material. If bobbin thread tension is too tight, or if needle thread is too loose, the bobbin thread
will pull to the underside of the material. If both threads are too tight, the material will be puckered
and drawn together by the stitches and the threads will break. Adjust the tensions as follows:
(2) Turn the machine pulley until tension screw is accessible.
NOTE
Tension on threads should be as sufficiently tight as possible while still sufficient to
set stitch in material without breaking the thread.
(3) Adjust the bobbin thread tension with the adjusting screw (1) in the center of the tension spring on
the outside of the bobbin case. Turn screw (1) clockwise to increase the tension and
counterclockwise to decrease tension. Check for lint or dirt under the tension spring.
(4) Lower the presser foot to close the tension disks. Adjust the needle thread tension by turning the
serrated nuts (1) clockwise to increase tension and counterclockwise to decrease tension.
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