I just got a new singer 4423. it stitches just fine for a while, then the top thread becomes a loopy knot underneath, snags, then returns to regular stitch. my old 4423 did the same but not as bad.

Re-check your stitch sample. Pull on the loopy thread. Is it really the bobbin thread, or is it the top thread looping under the fabric? FWIW, stitch problems appearing under the fabric are usually top thread issues, stitch problems on top of the fabric are usually bobbin related.

You can try this on both of your machines to see if it makes a difference.

Be sure to install a brand new needle.
Remove the top thread completely from the machine.
ALWAYS RAISE the presser foot and rethread from the beginning.
Make sure the thread path is correct.
Set the top tension to the midway point and retest your machine.

If the top thread is showing under the fabric, tighten the top tension, If the bobbin thread is showing on the top of the fabric, loosen your top tension. The perfect tension is when the two threads meet in the middle of the fabric.

...

...

Check the upper tension discs for lint: Raise the presser foot to open up the discs and blow or 'floss' between them. Any lint or thread in there will prevent them from giving the proper tension.

If that does not work then you may have a damaged hook and/or bobbin case that is snagging the thread. There are a few other reasons also, but you probably need to have it serviced to fix.

Good luck!

check that the bobbin underneath has the same thread as the upper bobbin and that you push all the way on the lever when sewing back and also, go full speed as this happened to me and that was my mistake. Hope this will help you :)

try adjusting the top thread tension one number or letter higher
and sew on a scrap piece of fabric till the stitches look normal.

Not Nancy, I am Ken, make sure the presser foot is up when you thread the mahine so the thread goes inbetween the discs, top tension about 4 or 5, the bottom thread should pull through with slight resistence, if it feels too tight slacken the bobbin case screw anti clockwise about a quarter of a turn and test and repeat until you get it right, remember to use only a good mercerised thread no thicker than a number 40

Make sure thread is not laying across the bobbin when you look down into the plastic slider that covers the top loading bobbin case. The bobbin on mine I observed was loose in the case so that as the machine ran, eventually the bobbin thread would jump out of the stitch finger (the silver piece to the far left of the bobbin case, past the tension slots). I solved this problem and so can you! Take the extra felt spool pin felt in your accessories kit that came with the machine, remove bobbin from case and drop this small felt circle into the bobbin case. Replace bobbin. On the 4423, the bobbin thread goes counter-clockwise and drops into the tension discs, and goes all the back until it falls into the space left of the silver stitch finger. Make sure take up level raised all the way up! Then pull the needle thread toward you until bobbin thread comes all the way up. If you start sewing and you actually can SEE the bobbin thread laying across the bobbin, STOP and tethered because that would mean your thread did not slide all the back behind the silver stitch finger--however, I assure you, if you go one step at a time, you did it correctly! You will be smiling in no time! Why? The felt helps to make the bobbin rest in the correct position to keep it from jumping out of the groove. I hope this helps you.
Jimmy

Check your top tension. It sounds like it may be too loose or the bobbin tension may be way too tight. Most likely it is the top tension that is incorrect though. The TOP tension effects the bottom side of the stitch and the bottom tension effects the top. If the top tension isn't tight enough it won't draw the thread up through the top side taunt enough and the excess underneath makes a big loopy mess.

Mine is doing the same thing. It's pulling the thread up from the bobbin and making a huge knot. Any suggestions. I've done all the above checks. Brand new needle, tension is on embroidery, threaded properly and no lint in bobbin compartment.

Hi Lou! This sounds like a tension problem--the tension on the top thread is too loose. Try using different color threads on the top and bobbin, then carefully rethread everything. Stitch a couple of inches and check the underside. If the top stitches look fine and the bottom ones are loose and loopy, and with the pressure foot down, tighten the tension. Move the knob or dial (whichever you have) just a little bit. Sew a couple of inches more, and recheck. Continue to sew and recheck, gradually tightening the tension, until you see little if any bobbin thread on the top or top thread on the underside of the fabric.

Let me know if this helps, ok?


Robbie

The top tension pulls the top thread up. The bobbin tension pulls the bottom thread down. A balanced tension is an an even knot between the stitches.

If the thread is messy on the bottom, the top tension is non-existent or is too low. The top thread tension dial should be on 4 or 5. Pull the thread out and re-thread the machine with the presser foot up. If it is still messy, perhaps there is a burr on the bobbin case snagging the thread.