Birds Nest

[jaunvie]

I've actually been having this problem for quite a while. It doesn't happen all the time, just kind of randomly.

I'll be sewing and in the middle of a stitch the top thread will catch, then break on the bobbin. The machine will then just continue sewing like normal. This doesn't happen at the beginning or end of a stitch. It's literally in the middle and I can usually hear it snap when it happens.

I've tried multiple tension adjustments and switching out needles, diffrent size threads and needle sizes. AND I've had this happen on multiple machines. (Again not an every day thing, but it can happen several times in a row then miraculously go away for a week or two) Also, I can't seem to reproduce it. 

[jaunvie]

I also caught it in the middle one time and this is what the bobbin looked like. 

Is it a random gremlin? Or is there something I can adjust? 

PS. It's happened to me on a few diffrent machines.  (Juki LU-563, Consew 206)

[Wizcrafts]

There is such a thing as sh_tty thread. Have you tried using a different spool or batch or thread?

As for adjustments, try altering the settings on your check spring mechanism. Since you haven't yet identified the machine in the photo, I can't be more specific. Most check spring assemblies have the following three adjustments.

1. Amount of downward travel. This movable curved bracket is usually set to keep the thread taut until the point of the needle passes into the material. Once the spring stops moving down there will be slack in the thread.
2. Strength of the moving spring. This is based upon the strength of the thread. It must have enough force to go all the way down to the bottom stop bracket, wherever it is set.
3. Position of the screw inside a curved slot which controls the slack in the available top thread on the down stroke. This setting is affected by the distance the spring can travel downwards after lifting on the take-up stroke. Moving the slot one way increases the slack and vice versa.

[DonInReno]

Is there a chance you’re moving the material too fast with hand pressure and deflecting the needle enough that the hook point is snagging the thread?   The more dull the hook point the more likely this will happen.   

[jaunvie]

Sorry, the machine used in both photos is the Juki LU-563. I have tried several different types of thread, size, brand, ect. With no real improvement. (Although some were definitely much worse) as well as new needles in diffrent sizes. 

Although I do sew a large variety of things, my typical set up consists of

1. the Juki LU-563

2. size 18 or 20 organ needles (depending on material)

3. size T-90 weight UV bonded polyester thread (A&E, though I've used sunguard and Tenara)

4. Sewing marine grade Sunbrella or Weather Max canvas

And this is an issue that has gone on for many years. (I've been sewing professionally for 30 years now) It doesn't happen often enough to really cause too much concern, and even when it does the top thread becomes "tied in" enough that it really doesn't affect the strength of the stitch. It's more of one of those little annoying things that I've been meaning to try and really figure out for a while now. 

Thanks for the suggestions (I didn't know about the #1 adjustment to the check spring) and for any future suggestions anyone might give. 

[CowboyBob]

It is best to start with a simple thing,when was the last time you cleaned in between the tension discs?Alot of the polester thread is fuzzy & the lint builds up after while.

It's real easy to take the nut & spring off,then the release washer,then take the discs out & look in between them for lint & sometimes there might even be grooves that the thread wore into thereby not allowing them the grip the thread like they should.

[Constabulary]

Have you checked the bobbin case opener? Is it working properly or is the thread probably handing there?

Or do you have a tension release while sewing maybe because foot rests on foot lift pedal or knee is touching knee lift lever? Just guessing.