The Rotary Driven Machine

If your rotary driven machine needs adjustment, always start problem solving by replacing the needle and testing the results. The needle could be bent or dull and changing it may easily solve the problem. Make sure the needle is in correctly with the long slotted groove forward. If changing the needle does not solve the problem, then move on to these instructions on timing the machine.

Timing

To understand timing better we must first understand how the machine works. There are two systems that must be kept properly related to one another in any sewing machine. First, there is the needle system. Secondly, there is the bobbin system. Working together these two systems are responsible for the proper formation of the stitch. If the machine begins to skip stitches or break thread check the relationship of these two systems.

It will be helpful if a little attention is devoted to the theory of sewing machine operation. The needle penetrates the fabric and reaches the bottom of its stroke about 1/2 inch under the fabric. It then starts up again. There is a groove on the front of the needle which allows the thread to be pulled upward with the needle there. But there is no similar groove on the back of the needle. As a result, the thread on the back side of the needle is held in place by the fabric and a loop is formed as the needle is withdrawn. The "gib" hook swings past the back of the needle roughly 1/4 inch under the fabric and catches this loop of thread. That loop is then pulled all the way round the bobbin cage by the rotation of the hook. This is what forms the locking stitch. The take up arm completes the stitch by pulling the upper thread tight. And the process repeats itself.

If the machine has a full rotary mechanism the bobbin thread hook swings round and round in a complete circle rather than oscillating back and forth. This rotary mechanism is smoother, faster, and more precise than an oscillating mechanism. But it is often more sensitive to minor maladjustment.

Steps to Proper Timing:

Step 1. Determining the Proper Rotation of the Gib Hook

On the front of the machine set the stitch width to the straight stitch position. Turn the balance wheel toward you until the needle bar (202-07 see illustration "A") is at its lowest point of travel. Near the top of the needle bar two marks have been scratched. Locate the needle bar timing mark plate (202-04), unscrew it and lower or raise it to the top most mark on the needle bar and tighten it down. This plate only serves as a reference point for timing. (If the timing mark plate does not have enough movement then lower or raise the needle bar (202-07) instead. See set screw (202-15).) Turn the machine over manually again till the 2nd mark on the needle bar is at the finger at the bottom of the needle bar timing mark plate—at this point the needle has been raised 2.2 mm from its lowest position.

At this 2.2 mm needle height set the gib hook on the rotary hook assembly (204-05) at the central line of the needle Illustration A and also as close to the needle as possible without touching Illustration B. To do this loosen the three set screws on the shaft of the rotary hook assembly. The entire assembly can now be moved left or right and also fore and aft. Position the gib hook so the space between the back of the needle and the rotating hook is about .05 - .1 mm (very, very close) and the point of the hook is at the center of the needle, then tighten the three set screws.

These adjustments can be seen more easily if the presser foot and throat plate are removed.

Step 2. Setting the Needle Bar Height

Now set the stitch width to maximum zigzag and turn the balance wheel forward manually until the needle is on the far left as you face the machine Illustration C. The shuttle hook point should cross exactly past the top of the eye of the needle as the needle is coming up from the bottom of its stroke on the extreme left (if the needle bar is too high or low, release its set screw (202-15) and raise or lower the needle bar. Retighten the set screw.

These adjustments can be seen more easily if the presser foot and throat plate are removed.

Upon reassembly, test the machine at maximum zigzag width. If it skips stitches on the left, the hook should be rotated counterclockwise. If skips are on the right, rotate the hook slightly clockwise. If the skips are randomly right and left, the needle bar is either too high or the shuttle point is too far from the back of the needle.

Step 1.
Determining the proper rotation of the Gib Hook

Getting to the Underside of the Machine

Any time there is a need to work on the shuttle assembly, replace bobbins or change feed dogs, we recommend that the machine be tilted back and rested on a spool of thread or some other sturdy support. Tilting the machine back so far that it rest on the surface on which it is sitting may damage the electrical cords.
Also be aware that since there is no cutout in the wooden case for the needle slide plate, it must be closed when the machine is lowered into the case.