Cobra 26 thread binding around bobbin shuttle.

[bdeming]

Hey there, I might not be using the correct terminology so pardon me.

I recently bought a Cobra Class 26 (JUKI 341 Clone). I have an intermittent thread binding issue, notable by its popping/crackling noise when the bound  thread is released and causing the thread to jump back and fray.

I'm running size 138 thread with a 135/16 size 22 Schmetz needle. I've tried adjusting the timing, retarding, advancing and setting it spot on and this issue persists. I've also tried adjusting the bobbin and needle tension. 

This issue occurs all throughout the sewing process, not just in the starting phase. 

 

Any potential solutions would be helpful! I took a video and linked to it below

[Wizcrafts]

The thread stub should not be attached to the bobbin latch! Remove it asap. I recommend installing the bobbins backwards to the flow.This keeps the bobbin thread under constant even tension.As for the tightness in the top thread, adjust the check spring to give more slack thread. That is done by rotating the thread check disk assembly to the right on systems like your machine. Loosen the little screw inside its curved slot, then loosen the nut on the front. Turn the disks to the right and lock it back down.

[bdeming]

2 hours ago, Wizcrafts said:

The thread stub should not be attached to the bobbin latch! Remove it asap. I recommend installing the bobbins backwards to the flow.This keeps the bobbin thread under constant even tension.As for the tightness in the top thread, adjust the check spring to give more slack thread. That is done by rotating the thread check disk assembly to the right on systems like your machine. Loosen the little screw inside its curved slot, then loosen the nut on the front. Turn the disks to the right and lock it back down.

Hi, thank you for the information however I, in my inexperience don’t know all the terms you describe like the thread stub. I followed the video below on the procedure for threading the machine. In the video it instructs to feed the thread from the bobbin, through a slot then to be placed under the bobbin latch. If this is incorrect please let me know

 

https://youtu.be/HV2NDZZq7MM

[purplefox66]

Take the bobbin out. There is thread around the latch that holds the bobbin in place. Do that and your problem is solved.

Edited February 2 by purplefox66

[Uwe]

The threading is indeed correct according to the video by Leather Machine Co. you referenced.

Here’s a screen shot from that video:

 

This hook and bobbin case is different from what I have on my Juki LS-341 (your Class 26 is mostly a clone of the Juki, aside from the hook, apparently)

 

 

The orientation of the latch arm that you fold down on top of the bobbin is pointing the opposite direction on my Juki. On the original Juki style hook, the bobbin thread stays below the triangular piece that the bobbin case opener pushes against.

Previous posters expected to see the bobbin thread to have a path like on my Juki, I think. 

On your style hook the bobbin thread does indeed get threaded to the top of the latch arm, it’s clearly designed that way. The hook design on your machine reminds me of hooks I’ve seen on modern Durkopp Adler machines. 

Hook design used in the Durkopp Adler 867, with a very similar bobbin latch arm and thread path to your machine:

 

So I doubt that the thread path is the cause of the issues you’re experiencing. From watching your video, it appears to me that two things are not quite right:

 

1. The thread occasionally does not slip easily into the cutout on the underside of the throat plate, where the thread has to wrap around the tab. You may have to adjust the finger (bobbin case opener) that pulls back on the bobbin basket to open the passageway that the thread has to slip through. (See video below)

 

2. The thread also appear to be let go too late from the gib that’s on the bottom of the hook. This indicates to me that the thread take-up lever starts pulling up on the thread before the hook has let go of the thread. This snag may cause loops at the bottom and also audible snapping sounds. Advancing the hook timing *should* help with that. 

 

This video shows how the stitch cycle works on my Juki LS-341. 

 

This video shows in more detail how that bobbin case opener is supposed to work:

:

This video illustrates the problem of the thread not being let go (cast off) by the hook gib soon enough (different machine than yours, but same issue). Advancing the hook timing (making the hoo tip arrive earlier at the needle) fixed the problem shown in this video:

 

 

Hopefully these videos will help get you started on your path towards figuring out what the problem might be on your machine. 

Edited February 2 by Uwe