Thread bunching under the fabric

Why the thread balls up underneath

A wad of thread on the underside of the seam, often with a clatter from the bobbin area, is called bird-nesting. It looks like a bobbin problem, and almost never is. Brother, Singer and Janome all trace it to the top thread: when the top thread is not held by the tension discs or has missed the take-up lever, nothing pulls it back up after each stitch, and the slack piles up under the fabric. Singer's 4423 manual puts it in one line: looping or bird-nesting on the underside means the upper thread is not threaded correctly.

The fix, in order

1. Stop sewing. Turn the machine off. Cut the threads above the fabric and pull the fabric gently away; cut the nest from underneath rather than yanking it. On drop-in machines you may need to take off the needle plate to clear it.
2. Pull the top thread out completely.
3. Raise the presser foot. With the foot down the tension discs are closed and the thread sits on top of them instead of between them. This one step fixes most nests.
4. Raise the needle and take-up lever to their highest point by turning the handwheel toward you.
5. Rethread the whole top path in your machine's order, making sure the thread goes through the take-up lever.
6. Sew a test seam on two layers of scrap. Hold both thread tails for the first two or three stitches.

If it still nests with the top thread correctly threaded, the top tension may be too loose. Janome's HD3000 table lists exactly that, along with a needle too heavy or too fine for the thread. Turn the tension up a step and retest.

What it usually is not

• Bobbin tension. Singer says the 4423's is set at the factory and should not be touched. Loops on the top of the fabric are the bobbin's side of the problem.

On your machine

• Brother XM2701 and LX3817: Brother's answer for tangled thread on the wrong side is to rethread with the presser foot raised and the needle at its highest.
• Brother CS7000X: the same fault can stop the machine with a beep and an E6 code. Clear the tangle and rethread.
• Singer Heavy Duty 4423: rethread the top before touching the dial; the basic tension is 4.
• Janome HD3000: rethread, then tighten the upper tension if loops persist.
• Juki TL-2010Q: Juki's cure for poor stitches is balancing needle and bobbin tension; do the bobbin drop test.
• Vintage Singers (Featherweight, 15-91, 401A): make sure the thread went between the tension discs and up under the take-up spring into its fork, as Singer's threading steps describe.