How do you determine if the sub tension knob is too loose on my Juki TL2010Q? My stitches are not uniform and some have a slight zig zag.

If the zig zag function on your Elna Carina sewing machine is not working, there could be a few possible causes:

1. Incorrect stitch selector: Make sure you have selected the correct stitch on your machine. Double check that you have selected the zig zag stitch, and not accidentally switched to another stitch.
2. Incorrect stitch width: The stitch width knob on your machine controls the width of the zig zag stitch. Make sure that the stitch width is not set to zero, as this would prevent the zig zag function from working. Adjust the stitch width to the desired size.
3. Tension issues: If the thread tension is too tight or too loose, it can affect the zig zag stitch. Check your thread tension to make sure it is set correctly.
4. Clogged machine: Dust, lint, and debris can accumulate inside your sewing machine and affect its performance. Clean your machine thoroughly, including the bobbin area and the feed dogs.

If none of these solutions work, it may be necessary to have your machine serviced by a professional.

Yes, because a zig zag stitch is creating a wide stitch and the tension on the thread is going to pull the fabric within the seam together, you can't seam thin fabric with a wide zig zag. It will "tunnel together". If you are using this stitch to neaten a raw edge, then try using the serpentine or three step zig zag where the needle pierces the fabric 3 times in each leg of the zig zag, this will give better results.

could you be looking at the zig zag indicator? try turning it and see if your machine does a zig zag stitch. There might also be a tiny knob to hold the zig zag stitch size indictor in place

you start with the broad zig zag stitch bar across the top
then you go down the left side using a smaller zig zag stitch
then you make the the broad zig zag stitch at the bottom
then you make the smaller zig zag stitch on the right side
all the way to the top broad zig zag stitch & your done
the right side zig zag does not go beyond the top broad zig zag
stitch

try changing the needle
adjust the top tension if nessary

it's very possible that the machine is slightly out of time & needs to be service at a sewing machine shop
is the fabric & thread & needle compatable with each other?
did you use every thread guide when threading the machine?
is the bobbin in correctly?
is the bobbin warped?

Usually thread too loose on the bottom is caused by the upper tension being too loose. The top and bottom tensions work together with the top thread making the underside of the stitch seem too taunt or too loose and the bobbin thread causing the top side of the stitch to be loopy or too tight. Select a large zig zag stick and sew a couple of inches. Then examine the stitch. It should look identical on both sides. Look to see which side is drawn too tight, the zig zag being smaller on that side with threads from the bottom threads pulled through. Then adjust the two tensions so that they make a uniform, identical stitch.

Also, when the bobbin tension is right you can hold the bobbin dangling by the thread and it won't spool out to the floor but will let loose a bit with a slight flick of the wrist. Too loose it will just spool out. Too tight and it won't drop at all. When you get that set right then do the above zig zag test to see where the top tension should be set.

sometimes when you reset the top tension dont forget to reset the bobbin tension so try to tighten the bobbin tension

The three front dials are as follows....left to right-Stitch width, type of stitch, and stitch length. The dial on the top adjust the top tension.

For straight stitch you want 0 stitch width, straight stitch, 3 for stitch length.

For zig zag you want turn your stitch width to how wide you want the zig zag, choose zig zag stitch, and choose how close you want the stitches to be on the stitch length dial. Practice on a piece of fabric. Usually for zig zag you will want to loosen your top tension a little bit.

Because it is almost a straight stitch but the needle continues to move in a zig zag fashion is reason to believe it is in a long stitch. By changing the number of stitches per inch there will be a very noticeable looking zig zag stitch.