Zigzag stitch problem, walking foot machine

[Ted B]

I have a Thompson Mini-Walker walking foot machine. Lately in zigzag mode, after several inches of perfect stitches, there are several with an huge excess thread loop on the bottom. I'm sewing 2-4 layers of Sunbrella 9 oz. canvas. And there is always a dark grease/oil stain visible on the thread on that stitch. And the top thread at those points are pulled over way too tightly.
One top side photo and two bottom side photos are attached.
Machine is in good repair and is oiled correctly. I wiped ALL of the oil off the shuttle area and the problem persists. There are no nicks on the gib hook or cap spring. The side clearance from hook to needle is in spec. The hook to needle rotation timing was in spec last time checked.
What could cause the top side thread mark? And what is wrong
Is Deck; Rigging, Sails the best forum for this?
Thanks for any advice.

[chris mac]

My sailrite was behaving similar. I took apart the tension adjustment assembly, it had some thread fibres built up inside. After cleaning it out it worked properly again

[Bill O]

Agree, looks like a tension issue vs. anything broken for the zz mechanism.

[tkeithlu]

The tension screw controls.....the tension. The tension controls the "pull" on the thread. A loop means no tension to pull it tight. Amen on Chris and Bill. Time to tear down your tension screw, which is far more likely the problem than fractured metal.

[Bill O]

We've had/repaired the fractured metal internal arm for the zz before and the way the stitches look, its not that.

[smbdyiam2]

30 years as upholsterer. Never used A thompson . Did use many different singer and Phaff. Looks like tension. Either not threaded right ,tension adjustments off, or dirt lint build up. Just a little under that tension spring in bobbin case will play all kind of tricks. I would clean, clean, then rethread and check every tension. Will find it and then say Oh I should have realized this. good luck
Lee

[Mike Banks]

Thread tension or cheap thread of uneven diameter or containing tiny lumps of fibre is almost always the cause of too loose or too tight threads. If the thread it s top quality, and use nothing else if you want your seams to last, then it must be the tension settings improperly set or somehow going off their proper settings. The oil is probably coming up from the feed claws, since you seem to have wiped the excess oil from everywhere else.

[JPA Cate]

No Thompson experience. My old Pfaff would do that if it were mis-threaded. I would also look for threads jammed as suggested above: I suspect that's what you're going to find.

Good luck with it.

Ann

[Sailing4Jesus]

The problem is quite clear. It is Zigging when it should be Zagging.

Senior Chief

[JonathanX]

I have the impression the thread is very soft or may be old. Try with another one.

[smbdyiam2]

I still believe problem is tension or dirt. I still have a bunch of thread that is over 20 years old. Has not been wet or in sun. Still as strong as 20 years ago. If he had been using his thread and didn't get wet or sunlight , it should still be good. But if he has used the machine it can get dirty or out of tension ,generally not threaded right. I still do a little for my self. My old singer still runs. Better than I do.

[MCOS]

Upper tension is too tight or bobbin tension is too loose. I have a brother and a sailrite. I have found that some thread will do this where other threads work fine. Rather than adjusting for odd thread, I use the same thread for most projects.

The upper tension is easy to adjust. The pulled through bottom loop indicates the upper is too tight. It will start out sewing ok until the tension builds up and then will pull the lower loop.

If you find the seam is too loose after running a seam and need to make the stitching tighter you may have to adjust the bobbin tension. There is a screw on the side of the bobbin. Turn in for tighter, out for looser. Generally the tension should be enough to keep the bobbin from unwinding when you hold the thread and suspend the bobbin. A gentle shake should allow the bobbin thread to feed out.

[MCOS]

Also, automotive spray carburetor cleaner can get rid of grime in hidden areas. Spray on and blow off with compressed air.

[smbdyiam2]

Originally Posted by MCOS

Upper tension is too tight or bobbin tension is too loose. I have a brother and a sailrite. I have found that some thread will do this where other threads work fine. Rather than adjusting for odd thread, I use the same thread for most projects.

The upper tension is easy to adjust. The pulled through bottom loop indicates the upper is too tight. It will start out sewing ok until the tension builds up and then will pull the lower loop.

If you find the seam is too loose after running a seam and need to make the stitching tighter you may have to adjust the bobbin tension. There is a screw on the side of the bobbin. Turn in for tighter, out for looser. Generally the tension should be enough to keep the bobbin from unwinding when you hold the thread and suspend the bobbin. A gentle shake should allow the bobbin thread to feed out.

basically right On tension of bobbin sometimes a little lint builds up under that tension bar that the little screw tightens and needs to be taken off and CLEANED then put back together. Same thing can happen to top tension but not as often. this is what I was saying in prior post clean ,clean. thanks lee

[Ted B]

Thanks all very much.


CLean: I think it's clean. Shuttle, bobbin, and tension assemblies disassembled and cleaned. No jammed threads or lint.


Top tension control: am very familiar with its cleaning, setup, and adjustment. I forgot to mention the stitching is perfect in straight stitch mode, only a zigzag problem. So don't see how it could be top tension. It is threaded correctly.


Shuttle parts: I just showed my shuttle retaining ring, gib hook and bobbin to a local sewing repair guy. He thought they looked undamaged and clean. He couldn't explain the dark thread stain exactly where there was a big loose bottom thread. BTW, I didn't mention the top left photo was the top surface. The other 2 were the bottom surfaces. If you look carefully you can see the bottom dark stain at the loose thread- distinct from the thread shadow close to it.


Thread: the repair guy also mentioned it could be bad thread. Mine is the best Sailrite V92 polyester thread. He said he has seen a bad section within a large spool cause loose loops. So I put brand new Sailrite pre-wound bobbin thread on top and bottom. Same problem.


Feed dog: Mike Banks' comment on "feed claws" was interesting. The feed dog bottom side was not oily but has a flat blackened finish, not paint. The clearance between the bottom of the feed dog and the shuttle retaining ring cap spring is VERY close. Maybe 1/32". Question: as the thread goes around the Class 15 bobbin to make a locked stitch- does it go ANYWHERE near the bottom of the feed dog?


Thanks all