Timing the Needle with the Shuttle

Figure 9-5.0iling points at the base of the machine

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2. Move the needle bar up or down as required; and then tighten the screw. 239.443 Figure 9-6.—Timing needle with shuttle. be in proper time for the machine to function properly. See figure 9-6. Timing the Needle with the Shuttle If a class 31 sewing machine does not form the lockstitch, if it skips stitches, or if it frays or breaks thread, the needle is not moving in the proper relationship with the shuttles motion. First make sure you have the right needle. Check the needle for the correct class, variety 16 x 87, and size. Insert the needle in the needle bar (long groove to the left) as far as it will go (fig. 9-6). Next compare the needle stroke to the shuttle stroke. To do this, remove the throat plate. Turn the balance wheel toward you until the point of the shuttle on its forward stroke reaches the center of the needle while the needle is on the upstroke. At this time, the needle bar should have risen 1/10 inch and the point of the shuttle should be 1/16 inch above the eye of the needle, as shown in A o f figure 9-6. NOTE: Prior to making adjustments to the sewing machine, always follow the troubleshooting chart in Table 9-1. If the needle eye is not in this position, the following steps should be taken: 1. Loosen the needle bar connecting stud screw, as shown in B of figure 9-6. 3. Rotate the balance wheel through the full cycle to check the timing. 4. Replace the throat plate. Timing the Feed Dog with the Needle The feed driving eccentric is an adjustable connection between the arm shaft (the shaft in the head) and the feed rock shaft (first shaft beneath the bed of the machine). If the feed mechanism is properly timed, the feed dog should be on its downstroke and level with the throat plate when the point of the needle reaches the material. If there is a twisted knot every 1 to 2 inches on the bottom of your material, check the timing of the needle before adjusting the feed mechanism. To adjust the feed eccentric, first lower the stitch regulator to the lowest position so the machine forms its longest stitch. Turn the balance wheel until the feed dog is on its downstroke and is flush with the throat plate. Move to the rear of the machine and take off the arm side cover. Turn the balance wheel away from you until the feed eccentric collar setscrew is visible (fig. 9-7). Hold the collar with your left thumb. Loosen the screw and rotate the balance wheel away from you until the needle, on its downstroke, reaches the material. Tighten the setscrew. Rotate the balance wheel to check the timing. Recheck the timing of the shuttle point with the needle. When you time the feeding mechanism, you may throw the needle out of time with the shuttle. 239.444 Figure 9-7.—Feed eccentric. 9-6

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