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[ShiroChaan]

I was sewing a seam and my machine was acting fine and then, when I pulled the fabric away there was a TON of thread in the seam... I cut it off to take a picture:

http://i77.photobucket.com/albums/j7...n/snapshot.png

What happened and how do I prevent it from happening again?

[benihime]

your bobbin could have been wound incorrectly or the tension could be wrong

[Aesceus]

Re thread your machine and make sure your bobbin is clear of any obstructions. This happens to me a lot and it's usually because I suck at threading or part of it came undone. If you need to, rethread your bobbin, too, it might have caught the 'start' of the thread and pulled them both at once.

[Penlowe]

That is commonly called a Birds Nest, all the above advice is good.
Birds Nests most commonly happen because an amazingly small soft bit has got to the wrong location within your bobbin housing. It could be lint, a stray thread, or the thread off your spool or bobbin going awry due to being threaded incorrectly.

when I get a birds nest I do the following:
- remove spool and bobbin from the machine, fully unthreading it
- remove the bobbin race (where I usually find big grey lumps of lint, my most common enemy)
- clean the bobbin race & race housing with a q-tip dipped in sewing machine oil and/ or canned air*
- clean the upper thread race (all the places your thread goes on it's way to the needle)
- rethread & start again.

99% of the time this does the trick.

* canned air is not recommended for computerized machines because it can send the fluff up into the circuit boards, which is bad juju.

[ShiroChaan]

It worked! Thank you!! Now to post a separate question about skirts...