Intermittent tension issue

[hanns]

Hello,

I've run into an issue that I haven't been able to track down with a new 1541S clone machine (Thor).

The bobbin thread intermittently shows prominently on top. This originally happened with size 138 thread (black belt photo). I am using 207 in the brown leather photo to make it more visible with black in the bobbin and white on top.

Things I have checked/tried:

• No spool snags
• Thread is pulled directly over top of spool.
• New needle/needle is large enough for thread size
• Tension discs are clean
• Machine is threaded correctly & thread is not snagging in the path (that I can see)
• Bobbin tension set based on drop test. Also tried higher tensions.
• Talked with a a technician at the seller. Got to a point where we could hide the issue by dialing in tension, but never really eliminate it or identify the source of the inconsistency.

I noticed the bobbin thread shows less often when the bobbin tension is set very high. It still happens, just very occasionally. Setting bobbin tension lower (and then adjusting the needle tension to compensate) seems to make it happen more frequently. I'm almost wondering if something is snagging in the bobbin area. Could an issue with the bobbin case cause this behavior?

Has anyone seen this before or have other ideas I should check?

Appreciated.

[Wizcrafts]

Buy different thread.

[RockyAussie]

I think that I agree with Wizcrafts about changing the thread but will add that I think that the needle hole looks a little wrong as well. If it is an LR shape then turn it slightly more around and see if it behaves any better. With the bobbin thread ....try pulling it up when it is in the machine and feel if there is any variations in pressure. If there is it could be bad bobbin winding (most common) or the bobbin is rubbing in the case. Try a different bobbin.

[bj139]

Overloaded bobbin with thread rubbing on inside of case?

Were the tracks in the brown belt sewed with a full bobbin starting from the bottom track?

Edited May 19, 2021 by bj139

[DonInReno]

I recently purchased the most idiotic gadget that I swore would never be worthwhile - a spring scale that reads up to 100 grams.    I don’t need one, and if a bobbin drop test can’t be done on a vertical hook machine it’s easy enough to guess and adjust accordingly if the material needs it.

About 30 grams of weight is roughly what a bobbin drop test shows in the machine I normally sew 138 with.    No surprise there - having a spring scale tell me that isn’t helpful...right?

Well....I had three vertical hooks and went to set the same tensions on them and discovered a lot of variation depending on slight differences in direction of pull.   The worst offenders had the roughest finish on the edges of the tension spring.    Tensions can easily double with minor changes in thread angle.   I hadn’t expected that.

Polishing the edges with 1000 grit sandpaper smooths things out considerably.   

Honestly it doesn’t sound fun to polish every tension spring that lands on my healing bench so I’m not going to check unless there is some kind of problem.  Sometimes ignorance is bliss.  

....and I’ve changed opinion of the thing - it’s rarely used, but well worth the $10.   I wouldn’t recommend the scale to anyone else, but I would recommend polishing the edges of the bobbin tension spring if you have any doubts about it.    Use a good screwdriver and don’t loose the screws!

If I were in your situation I’d first try a different high quality thread and make doubly sure there are no burrs or sharp edges anywhere in the upper and lower thread paths - including polishing the bobbin spring.

 

 

[kgg]

Any chance of a photo's showing the tread path from the spool to the eye of the needle. Also the distance from the bottom of the spool to the thread hole just above the spool of thread should be approximately 2.5 times the height of spool of thread. Are you using a 1 lb spool of thread or 8 oz? Is the thread a brand name or a Chinese brand thread?

kgg

[hanns]

41 minutes ago, kgg said:

Any chance of a photo's showing the tread path from the spool to the eye of the needle. Also the distance from the bottom of the spool to the thread hole just above the spool of thread should be approximately 2.5 times the height of spool of thread. Are you using a 1 lb spool of thread or 8 oz? Is the thread a brand name or a Chinese brand thread?

kgg

It's 8oz spools of Amann (138) and A&E (207) brand thread from Thread Exchange. I've added some pictures showing the thread path. The black spool here was for loading a bobbin, but isn't actually hooked up to anything.

Ignore the sponge. That was something the service tech had me try to ensure the thread wasn't getting caught up as the take up lever moved up and down, but it ultimately didn't help the issue.

1 hour ago, RockyAussie said:

I think that I agree with Wizcrafts about changing the thread but will add that I think that the needle hole looks a little wrong as well. If it is an LR shape then turn it slightly more around and see if it behaves any better. With the bobbin thread ....try pulling it up when it is in the machine and feel if there is any variations in pressure. If there is it could be bad bobbin winding (most common) or the bobbin is rubbing in the case. Try a different bobbin.

This was a NW type needle that is meant to make a slanted stitch. However the slants are appearing on the back rather than the front, so maybe that's related. I'm not sure why (installed needle per directions), but I'll try moving the needle around a bit and see if it helps. I think for my next test I'll try a diamond needle and see if the issue goes away.

59 minutes ago, DonInReno said:

I recently purchased the most idiotic gadget that I swore would never be worthwhile - a spring scale that reads up to 100 grams.    I don’t need one, and if a bobbin drop test can’t be done on a vertical hook machine it’s easy enough to guess and adjust accordingly if the material needs it.

About 30 grams of weight is roughly what a bobbin drop test shows in the machine I normally sew 138 with.    No surprise there - having a spring scale tell me that isn’t helpful...right?

Well....I had three vertical hooks and went to set the same tensions on them and discovered a lot of variation depending on slight differences in direction of pull.   The worst offenders had the roughest finish on the edges of the tension spring.    Tensions can easily double with minor changes in thread angle.   I hadn’t expected that.

Polishing the edges with 1000 grit sandpaper smooths things out considerably.   

Honestly it doesn’t sound fun to polish every tension spring that lands on my healing bench so I’m not going to check unless there is some kind of problem.  Sometimes ignorance is bliss.  

....and I’ve changed opinion of the thing - it’s rarely used, but well worth the $10.   I wouldn’t recommend the scale to anyone else, but I would recommend polishing the edges of the bobbin tension spring if you have any doubts about it.    Use a good screwdriver and don’t loose the screws!

If I were in your situation I’d first try a different high quality thread and make doubly sure there are no burrs or sharp edges anywhere in the upper and lower thread paths - including polishing the bobbin spring.

I was actually thinking about a gauge. I have a small one that I use to calibrate bobbin tension on my older Singer domestic machines. $10 for a heavier gauge isn't a bad idea to have on hand. And if this keeps up in spite of other changes, having a closer look at the bobbin case spring sounds like a good thing to try.

2 hours ago, Wizcrafts said:

Buy different thread.

What thread works well for you? I've just been using stuff from Thread Exchange, but I'm open to other brands/sources.

Thanks for the suggestions everyone. I will report back when I've had a chance to test them.

[hanns]

1 hour ago, bj139 said:

Overloaded bobbin with thread rubbing on inside of case?

Were the tracks in the brown belt sewed with a full bobbin starting from the bottom track?

I was actually working with maybe a 50-25% full bobbin most of the time.

The brown piece was done from the top down. What changed along the way was tension on the bobbin (tight on top, looser on the bottom). Even with the settings for the top row where it looks good, the issue would crop up if I did a longer run of stitches. So it was never really eliminated even with very tight bobbin tension.

[RockyAussie]

Couple of things I would try here is 1st don't put the thread under that last little spring guide thingy as I have found that any little thing like that the can interrupt the flow after the spring tension disks can cause an issue and secondly I would make sure the first knob with the +/- on it is set very loose. Lastly ...make sure that you have the foot pressure down enough to not let the job raise up with the needle coming out as that will also give a very uneven erratic stitch knot location.

[kgg]

The Thor Machine is similar to the Juki 1541 S but has Two extra thread tensioners (the top one with the + and - sign on it and the one located at the 9 o'clock position) which shouldn't matter, just a little more balancing needed. The tensioner system is like the the Juki 1508. I would remove the sponge in the vertical thread guide and move it up further with a very slightly tilt about the 12:30 o'clock position just to give a little extra angle on the thread going into the take-up lever. Some Juki's and clones in the 341 class have a felt pad that is inserted in the horizontal guide just below the take-up lever which I suspect the tech wanted you to insert the sponge into not the vertical guide as shown in your photo.

The Juki 1541 S and 1508, according to the Juki manual, has the thread leave that horizontal guide and go through the next guide on the "Right" side of the screw. This noted in the sufficiently noted in both Juki manuals for the threading diagram. I suspect that you need to thread your machine like a Juki 1508 not the 1541.

I see you are using a spool thread sock on the 8 oz threads. I would try not using them as they can give inconsistent thread tension and may not be perfect and catch / snag thread. Also I would try and lower the top arm and spool holder down so the thread doesn't have such a steep angle entering the first horizontal guide. I find the best angle is when the thread enters the first horizontal guide almost horizontally.

kgg