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Setting the Needle
Regulating the Length of Stitch - 14218_197

Aircrew Survival Equipmentman 2 - Aviation theories and other practices
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guide (10), which is located on the needle clamp. The needle is now threaded from left to right through the eye of the needle (11). After the needle is threaded as shown in figure 9-19, pass the thread down through the hole in the lifting presser foot (12). Draw about 4 inches of thread through the hole in the lifting presser foot with which to begin sewing. Notice that the lubricating cup has been bypassed. No lubricant is used on the threads and cords used in the manufacture or repair of parachutes. Removing the Bobbin Turn the balance wheel forward to bring the needle bar and thread take-up lever to its lowest position. With the aid of the shuttle opening tool or a small screwdriver, insert the blade end in the slot in the spring latch beneath the shuttle cylinder (fig. 9-20). Press the latch away from the cylinder and it will swing out. The bobbin will then slide out of the shuttle cylinder. Winding the Bobbin Place the bobbin on the bobbin winder spindle and push it up closely against the shoulder. The small pin in the shoulder must enter the slot in the bobbin. Pass the thread from the thread stand through the hole in the left side of the bobbin from the inside. Push the bobbin winder pulley up against the balance wheel, and place the bobbin winder Figure 9-20.—Removing the bobbin cylinder. 239.277 from the shuttle 239.278 Figure 9-21.—Replacing the bobbin. latch in position. Raise the presser foot and start the machine. The end of the thread should be held until a few turns are wound on the bobbin to prevent slipping. When sufficient thread has been wound on the bobbin, the bobbin winder will stop automatically. Replacing the Bobbin and Threading the Shuttle Take the bobbin between the thumb and forefinger of the left hand, as shown in figure 9-21. The free end of the thread should be drawn off from the underside toward the right. Place the bobbin in the shuttle cylinder as far as it will go. Draw the thread into the slot in the cylinder and under the tension spring into the delivery eye. Push the shuttle cylinder in until it is locked by the spring latch. There should be about 3 inches of thread hanging free from the shuttle with which to begin sewing. Regulating the Tension The tension on the needle thread is regulated by the thumb nut at the front of the thread retainer disks. The tension on the thread retainer disks should be just enough to cause the tension wheel to turn when the thread is taken from the spool. The tension on the bobbin thread is regulated by the small screw that holds the tension spring to the shuttle cylinder. To increase the tension, 9-16







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