Troubleshooting Stitch Quality

If you are encountering problems with stitch quality, check these things:

In this section, we will walk through the process of how a stitch is made and then troubleshoot issues.

Before you Start

Clean and oil the sewing head.
Use a cone of thread that has been proven to be good. The cone you used last week without issues is the cone you want to test the machine with. If the stitching problem disappears when using a proven good cone of thread, it might be that today's problem is being caused by bad thread.
Load the filled bobbin into the bobbin case. Check and adjust the bobbin tension using your Towa Gauge.
Load the bobbin case into the machine. Be sure to listen for the click that indicates the bobbin case is properly secured. If you don't hear the click, remove and re-install and listen again for that click.
Thread the top thread as per the diagram for your machine, and bring the bobbin thread up. Tip: After pulling the bobbin thread up, check to see that the bobbin thread still pulls freely.
Install a new 4.0 needle and make sure it is pushed all the way into the needle bar. There's a sight window about 1/4" above the needle screw, you should see that window filled completely by the end of the needle.
Load a good quality testing quilt sandwich. Muslin or other cheaper fabrics will not accurately represent how the machine will stitch on a quilt.

How a Stitch is Made

Screen Shot 2022-10-27 at 3.21.45 PM The hopping foot compresses the fabric layers as the needle is lowered. The needle enters the fabric, bringing the top thread under the fabric.

Notice that the eye of the needle is fully visible at the lowest point of travel. The top thread travels down the groove at the front of the needle to loop around the bobbin case.

If you are using an incorrect needle and thread combination, such as a thick thread with a small needle, the groove and the needle eye are too small to accommodate the thickness of the thread and thread breaks can occur.

The hopping foot continues to compress the fabric as the needle begins to rise. The friction of the thread against the compressed fabric as the needle rises causes a loop to be formed under the fabric behind the needle.

Screen Shot 2022-10-27 at 3.21.54 PM The hook captures the loop as the needle rises out of the fabric. Proper timing of the machine means that the hook reaches the loop at the exact time and location necessary to form the stitch. If the hook misses the loop, the stitch is not formed. If the hook point and needle are not close enough it can result in skipped stitches when the machine is pushed away from you.

The hook continues around the bobbin case, taking the top thread with it.

At this point, the loop of the top thread has excessive slack. The take-up lever pulls the top thread up to consume the slack and complete the stitch. When the top thread is pulled up, the stitch is complete and the formation of the next stitch begins.

Causes of Skipped Stitches

Skipped stitches occur when the rotary hook fails to capture the thread loop at the back of the needle. Skipped stitches can also occur when the rotary hook is not properly timed with the movement of the needle. Using the information we learned about how a stitch is formed, here is a summary of the possible causes:

#1 most common cause - The fabric layers are stretched too tightly on the frame. Make sure that the layers are LOOSE.
#2 most common cause - The needle size is too small. Generally the machine is adjusted for a 110/18/4.0 needle.

Here's a couple other things to check, if your skipped stitches are not caused by the solutions above:
The needle is installed backward. The belly bulge should face the front of the machine.
The hopping foot is not low enough to sufficiently clamp and hold the layers of the quilt.
The top of the machine is not threaded correctly. Refer to the diagram for your exact model.
The hook point and needle are not close enough. The required clearance is 0.0001" which is all but touching.
The hook timing is incorrect. You can use your timing tool to check the hook timing. Warning: the steps for using the timing tool are very precise and must be followed carefully and exactly.

Adjusting Stitch Tension

Once the quilt is loaded and you are ready to thread the machine, follow these steps to adjust the stitch quality:

- Pre-Test tension before stitching. When the machine is fully ready to stitch (including having pulled up your bobbin thread) you can pre-test your tension before beginning to stitch.
  A: Pull on the BOBBIN THREAD and sense the tension with your hand. As you pull, notice that it pulls smooth and light (maybe even "silky") and if there's any pulsation in the tension you feel, the pulsation should be very slight. A Towa gauge will help you identify any issues with your bobbin case. Several issues can occur with the bobbin which would cause pulsation, such as a bad bobbin, a bad bobbin case, lint somewhere inside the bobbin case, or even a poorly wound bobbin.
  B: Pull on the TOP THREAD and sense the tension with your hand. As you pull, notice that it pulls tight and "gritty". There should be little or no pulsation in the tension you feel. It must pull about 2-1/2x tighter than the bobbin or else your machine will not make a good stitch. If the top does not feel at least 2x the tension of the bobbin.... or if it feels tighter than 3x, this imbalance must be corrected. Top tension needs to feel 2.5x tighter than the bobbin or else the machine will not stitch nicely.
Test the tension by stitching a rectangle shape on your test quilt. Check the stitch quality on both the top and bottom. The top and back should look very similar to each other. Once the bobbin tension has been checked and the check spring tension has been set in the assembly, the only adjustment that should be made for the top tension is adjusting the intermittent tension. Tip: Loosen or tighten intermittent tension 1/2 turn at a time until proper tension is achieved.
If the thread on top is laying flat or you see lots of bobbin thread on the top but the bottom stitching looks good then you may have too much top tension. Loosen your intermittent tension ½ turn at a time until the stitching looks good.
If your top stitching looks good but the thread on the bottom is laying flat or you see lots of top thread on the bottom then you may not have enough top tension. Tighten your intermittent tension ½ turn at a time until the stitching looks good.

Top Thread Frays and Breaks

Probable Cause	Solution
Improperly installed or damaged needle	Replace the needle.
Restriction along the thread path	Check for proper threading. Make sure the thread cone points directly toward the first thread guide. The top thread should pull smoothly without jerking. Do not allow your arm or cords to rest against the thread cone.
The needle deflected out of alignment with the sewing hook	Use stronger (larger size) needles or do not pull fabric so tightly.
Improper needle bar height	Check the needle bar height.
Hopping foot too high or the stroke out of time	Adjust hopping foot timing so the foot holds the fabric still until the needle has risen approximately 3/8”.
Damaged hook point	Replace the hook.
Damage or burr at needle hole of needle plate or other thread handling part	Locate damage or burr and replace the part.
Too small needle for the thread being used	Use a larger (thicker) needle.
Rocking finger disengaged, tilting bobbin case base too much, or improperly adjusted	Adjust the rocking finger to eliminate stress on the thread.
The timing is off	Watch video instructions on Gammill.com or schedule a service call.

Loops on Bottom

Probable Cause	Solution
Improper threading or restricted top thread flow	Refer to the threading diagram and threading instructions.
Not enough tension on the top thread	Tighten Intermittent tension. Rotary checkspring knob should never be so tight as to stop the wheel from turning.
Checkspring improperly adjusted	Adjust the check spring.
Hopping foot too low	Adjust hopping foot bar height.
Bobbin case finger too deep in the notch	The finger should be approximately halfway to 2/3 into the bobbin case base. Adjust the hook retainer bracket (Finger).
Rocking finger improperly adjusted	Adjust the rocking finger.

“Eye Lashes” or “Railroad Tracks”

When stitches appear as a straight line with dots along either side, these are called eyelashes or railroad tracks because of the obvious resemblance. Eyelashes occur when the machine is moved too fast around curves or if the thread tension is too tight for one of the threads.

If eyelashes appear in curves, you should slow down the speed of the sewing head while stitching the curve. If the eyelashes continue to persist then adjust the tension as explained below.

If eyelashes appear on the top of the quilt, either the top tension is too tight or the bobbin tension is too loose.

If eyelashes appear on the back of the quilt, either the top tension is too loose or the bobbin tension is too tight.

Pokies

Pokies are little dots of thread showing along the stitch path. They generally occur when the top and bobbin threads are different colors. Even with the tension properly adjusted, pokies can and do happen. The best way to prevent pokies is to use the same color thread in the top as you do in the bobbin. Pokies can be less visible if a busy print fabric is used for the backing.