As a cost-cutting exercise, tough economic times have brought about resurgence in home sewing projects, especially among families with growing children. Since the invention of the eye-pointed needle in the 1800's, domestic sewing machines have evolved into reliable cost-effective units capable of producing a variety of plain or patterned stitches. However, regardless of the stitch type, a common problem is skipped stitches caused by the lower bobbin hook failing to pick up the upper thread.
Incorrect needle positioning is the most common cause of skipped stitches. When installing a new needle, the milled flat surface of the upper part of the needle shaft must face toward the needle set screw before tightening. This will automatically position the lower groove above the eye of the needle, called the “scarf,” so that it faces toward the pick-up hook on the lower bobbin mechanism.
A bent or blunt needle is the second most common cause of skipped stitches. A blunt tip forcing its way through the fabric may cause the tip of the needle to flex away from the lower bobbin pick-up hook. In addition, if the needle is bent, it may either hit the pick-up mechanism or position the scarf too far from the pick-up hook, thus preventing the hook from picking up the upper thread to complete the stitch.
Skipped stitches occur if the if the lower pick-up hook passes the needle scarf before or after the scarf cut-out reaches the correct position. Check the timing by first removing the screws securing upper and lower cover plates to expose the mechanism, and then removing the bobbin. Once that is done, rotate the hand wheel anticlockwise while watching the point of the needle. If the tip of the pick-up hook reaches a point just above the eye of the needle at the lowest position of the needle's stroke, the timing is correct. If not, either the needle height is incorrect, or the set screw securing the lower bobbin mechanism has worked loose causing the mechanism to slip.
Try to twist the lower bobbin mechanism on the drive shaft. If it doesn't move and the point of the needle is too high or too low when the pick-up hook coincides with the side of the needle, adjust as follows: Set the needle at its lowest position. Undo the set screw securing the upper vertical needle shaft and raise or lower the shaft so that the flat cut out needle section is positioned correctly. Check to see that the eye of the needle is just below the tip of the pick-up hook before tightening the set screw on the vertical shaft.
Undo the single set screw (or three set screws, if applicable) securing the lower bobbin mechanism to the horizontal drive shaft. Rotate the hand wheel anticlockwise until the flat cut-out section on the side of the needle is positioned at the lowest point of its stroke. Once that is done, rotate the bobbin mechanism on the shaft to the position where the pick-up hook reaches a point a half a millimetre before the cut-out just above the eye of the needle. Slide the bobbin mechanism in or out on the shaft until the inner face of the hook just clears the needle. Snug down the single bobbin mechanism set screw, or one of the three set screws if applicable, and rotate the hand wheel one full turn to double check the timing. Finally, tighten the set screw(s) securely. Reassemble the cover plates, replace the bobbin and thread the machine correctly before doing a test run. Note: If your mechanical ability is below par, ask a qualified technician to carry out the needle height and bobbin timing procedure.
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