Sewing machine trouble: uneven seams

[hutzelbein]

My sewing machine is driving me crazy. I haven't got a clue what's wrong with it; I think I have tried everything, unless somebody has an idea that I haven't yet had. The problem is, that the seam isn't consistently even. Every once in a while, it doesn't pull the thread coming from the top back up through the fabric. Sometimes it's hardly noticeable. Sometimes the top thread creates a small loop (on the bottom side). Here is one of the most extreme examples:





Of course I have tried adjusting thread tension: top thread tension as well as bobbin tension. I have used differently colored threads to better see where the threads meet. I do a lot of test seams, and I also sew two identical seams and pull the top thread out first, and then the bottom thread to feel how tight it is held. I tried to get the tension adjusted so that both threads need about equal force to pull out. And the seams look perfect for the most part. But every 40" or 50" or so, the top thread isn't pulled up properly. Most of the times it just creates a saw-tooth pattern for 2 or 3 stitches before it goes back to perfect:



I have been having this problem for about 7 months now. I brought my machine to a repair shop and had it serviced. During the last summer, the mechanism that lifts / lowers the foot got sluggish. This was fixed during the service. But afterwards the seam problems started.

I did contact the shop to find out what could cause the problem. They advised me to clean the slot where the top tension is set. There was no dirt in there. The problem persisted.

They advised me to exchange the needle and to try a larger needle. I did both. The problem persisted.

They advised me to change the top tension. I did that, and I also changed the bobbin tension. The seams got a bit better, but the problem persisted.

I brought the machine to the shop and tried to recreate the problem. Of course it didn't show as clearly as at home. But then I remarked that I had bought a new sewing foot, and it turned out that the foot didn't have a slot in the bottom and probably jammed the thread. I took the machine home without having it checked by a mechanic because everybody was very sure that this was what had been causing the problem. I went back to my old sewing foot, and things improved. But the problem never went away completely. With thin 1.0oz and 1.1oz fabrics in double layer hammocks, it still crops up now and then. Always in the channel. Although I have been OCD about top thread and bobbin tension since then. I never bothered about it before, and when I look at seams I did before that service, I don't see any loops or any saw-tooth patterns.

I'm completely lost now. I don't want to go back to the repair shop if I don't have to, because it's a one-hour drive (which is a lot for Europeans...), because it will cost more money, and I didn't get the impression that they had a clue either.

Has anybody had a similar problem and found a solution? Any ideas what could be causing it? Could it have something to do with the repair on the sluggish sewing foot? I tried opening the machine, but apparently you need to have special tools or know where to push. For what it's worth, it's a Pfaff creative 1475 CD. The problem now mostly occurs with Gütermann Tera 60, and when I do the channel seams of a double layer hammock made from thin 1.0oz or 1.1oz fabrics.

Thanks!

[hutzelbein]

I forgot: I also used different bobbins. For a time I suspected that it was due to the bad quality of some el cheapo bobbins I got off eBay. But the seams in the pictures where done with the best bobbin made by Pfaff.

[Peter_pan]

If your machine has a top loading bobber; when you drop in the bobber then wrap the thread to the clockwise direction there is a tiny slit that must capture the tread in the bobbin case... you have it correct if the tread is over the top of the visible bobber side with the viewing panel open... If it is within the bobber the slit was missed and must be rethreaded... FWIW this error causes the problem you are seeing.


Note: to get it right every time, use your right hand pointer finger to keep the thread on the sewing deck as you wind it IAW the threading pattern for the bobber thread.

Pan

[sqidmark]

With tera 60 may need a 100 needle. Use Jellyfish's technique of testing how well the needle slides down the thread. https://www.youtube.com/watch?v=XwynEzDwDoM

[hutzelbein]

If your machine has a top loading bobber; when you drop in the bobber then wrap the thread to the clockwise direction there is a tiny slit that must capture the tread in the bobbin case... you have it correct if the tread is over the top of the visible bobber side with the viewing panel open... If it is within the bobber the slit was missed and must be rethreaded... FWIW this error causes the problem you are seeing.


Note: to get it right every time, use your right hand pointer finger to keep the thread on the sewing deck as you wind it IAW the threading pattern for the bobber thread.

Pan

Hm, I'm not sure if I understand you right. You say that the thread has to run in the right direction and needs to be threaded correctly? I have a manual with pictures that show how to insert the bobbin. I have checked and re-checked this. Also, the shop checked me loading the bobbin. I always do it the same way, and they said it looks alright. I can take a couple of pictures, though, if you think that I do something wrong.

[hutzelbein]

With tera 60 may need a 100 needle. Use Jellyfish's technique of testing how well the needle slides down the thread. https://www.youtube.com/watch?v=XwynEzDwDoM

You're right; Gütermann recommends a 90 needle for the Tera 60, not the 70 I'm using. But I did try a 90, and it didn't solve the problem. It only makes it harder to sew thin fabrics like 1.0oz HyperD, since it pushes the fabric into the sewing plate. After I saw Jellyfish's video a couple of weeks ago, I switched back to 70 because the thread slides easily through the 70 needle. I don't think that's what's causing the problem. Especially since I had been using a 70 needle with Tera 60 for about 2 years and didn't have this problem. It all started after the dang service :/

[georgecarr]

If it's a metal bobbing make sure it's true. If it gets dropped or it's not straight from the factory it could get a little out of whack and cause uneven tensioning. I had this issue recently on one of my Jukis and it was a bobbin.

[hutzelbein]

If it's a metal bobbing make sure it's true. If it gets dropped or it's not straight from the factory it could get a little out of whack and cause uneven tensioning. I had this issue recently on one of my Jukis and it was a bobbin.

No, I'm currently using a plastic bobbin. I do have different bobbins - some no-name metal ones, some no-name plastic ones (some cheap ones off eBay, some more expensive ones from a sewing shop) and some expensive plastic ones made by Pfaff. They say they are their best bobbins. I think they are milled, not molded. I also used more than one bobbin of each sort. I guess that makes it less likely that the bobbin is the cause.

[hutzelbein]

I did mark my bobbins with a silver marker on the outside, to differentiate between Tera 60 and Tera 80. Unfortunately they don't sell differently colored bobbins for my machine model. Do you think the mark could make the bobbin run uneven?

[georgecarr]

I did mark my bobbins with a silver marker on the outside, to differentiate between Tera 60 and Tera 80. Unfortunately they don't sell differently colored bobbins for my machine model. Do you think the mark could make the bobbin run uneven?

Doubtful. Your right, doesn't sound like a bobbin problem. Seems like a tension issue. Hopefully the shop didn't assemble something incorrectly when they services your machine.