will loosen the upper thread tension causing the bobbin tension to draw the stitch into the material. A clockwise turn will tighten the upper thread, thus drawing up any stitch that may be locking below the material.

If you cannot correct the tension by adjusting the thread tension disc, adjust the bobbin tension. To do this, tighten or loosen the small screw nearest the center of the spring. This completes all the necessary timing and adjusting on the 111 W 155 sewing machine. If you still have a problem, refer to the troubleshooting portion of this chapter.

TROUBLESHOOTING

While making adjustments or timing the sewing machine, you may overlook a step or a faulty part. The troubleshooting chart (table 4-4) will help you locate and correct most problems.

If the sewing machine is binding (hard to turn), you can locate the problem easily. First, check the feeding action; then set the machine on zero feed and remove the throat plate. Turn the machine by hand. If the bind is still present, remove the arm shaft connection belt. If the bind is located in the hook-driving shaft, the machine will turn freely. Turn the balance wheel by hand. If the bind is located in the arm shaft, the bind will still be present.

SINGER SEWING MACHINES 31-15, 331K1, AND CONSEW C-30

Singer Sewing Machine 31-15, the 331K1, and the Consew C-30 are oscillating-type sewing machines that have a maximum speed of 2,200 stitches per minute. These sewing machines also make the standard lockstitch and are commonly called tailoring machines. As with the 111 W 155

Figure 4-12. - Upper thread unit.