Check spring range of motion

[Wyowally]

Thanks  Wiz!   I'll try what you suggest about timing. With mine although I think I've done it all correctly,  the needle bar/needle clamp will bump against the the presser feet when lifted manually. When I think I've got the needle 3/32" above bottom it does this. One other oddball thing - with the hook I've got, just about the time I get the checkspring jerk, the opening in the bobbin case hits the gap in the shuttle/hook and there's a little jump there, too. Don't know it they/re related. I'll keep playing and studying Uwe's videos.

[Uwe]

When I adjust machines I make sure the check spring engages a little to put some tension on the top thread when it’s about to get pulled through the gap between the bobbin case tab and the throat plate cutout. This will look a like secondary little jump of the check spring as it goes through the stitch cycle. 

This kind of contradicts the statement @Dave4 made in the original post at the top of this topic that stated:

“If my observations are correct, the check spring should not enter the game again until after the hook has carried the captured upper thread more than half way across the bobbin face on its journey to becoming a lockstitch.”

If the thread is too slack at the moment it gets pulled around the far side of the bobbin case, then it may not slip though the gap before it closes up again. This could cause a potential snag and loops.

I don’t have a separate video about it but I sorta-kinda mention it in the Juki LS-341 stitch cycle video at the 1:30 mark

 

 

Edited August 4, 2021 by Uwe

[Gymnast]

7 hours ago, Uwe said:

If the thread is too slack at the moment it gets pulled around the far side of the bobbin case, then it may not slip though the gap before it closes up again. This could cause a potential snag and loops.

@UweI looked at your video and noticed your comment, that the check spring should only engage a bit at this position in sewing cycle. After thinking a bit about that, I would guess, that it should depend on the thickness of the fabric. With higher thickness of fabric, you got more thread use and then more pull of the check spring should be expected at that point. Can you agree to that?

Edit: I am not so sure about this. I guess some trial or analysis in more detail is needed.

Edited August 4, 2021 by Gymnast

[Wyowally]

10 hours ago, Uwe said:

When I adjust machines I make sure the check spring engages a little to put some tension on the top thread when it’s about to get pulled through the gap between the bobbin case tab and the throat plate cutout. This will look a like secondary little jump of the check spring as it goes through the stitch cycle. 

This kind of contradicts the statement @Dave4 made in the original post at the top of this topic that stated:

“If my observations are correct, the check spring should not enter the game again until after the hook has carried the captured upper thread more than half way across the bobbin face on its journey to becoming a lockstitch.”

If the thread is too slack at the moment it gets pulled around the far side of the bobbin case, then it may not slip though the gap before it closes up again. This could cause a potential snag and loops.

I don’t have a separate video about it but I sorta-kinda mention it in the Juki LS-341 stitch cycle video at the 1:30 mark

 

 

Uwe, thanks again. Mine is snagging a little right at 2:25 in your video, like it is catching on the gib plate or something related.

[Wizcrafts]

Just now, Wyowally said:

Uwe, thanks again. Mine is snagging a little right at 2:25 in your video, like it is catching on the gib plate or something related.

Try advancing the hook a couple degrees. Also, loosen the set screw in the check spring disks and rotate them clockwise to the right of center. You might also have to back off the round nut on the shaft. I change my check spring centering often so I leave the set screw a little loose in the slot and loosen/tighten the round nut when I want to readjust the position in the slot. This setting gives more or less slack thread to the hook. I rarely change the bottom stop bracket once it is dialed in.

[Wyowally]

Wiz and Uwe, I'll try those ideas. Might be able to get a picture today. Thanks again. Still wonder if that 3/32" rise from bdc should make the needle bar bump into the presser feet when they are raised. Mine does that, so I can't manually turn the wheel with the feet up!

[Wizcrafts]

Just now, Wyowally said:

Still wonder if that 3/32" rise from bdc should make the needle bar bump into the presser feet when they are raised. Mine does that, so I can't manually turn the wheel with the feet up!

So, lower the presser and vibrating foot bars until they clear the needebar.

[Wyowally]

I can lower them. Think I was going for maximum lift, which I don't need. Thinking the 3/32" is priority over manual lift height.

[Wizcrafts]

2 hours ago, Wyowally said:

Think I was going for maximum lift, which I don't need.

You can probably find lower profile feet, or grind down and polish the bottom of a standard set.

[Wyowally]

I think this might have some sort of aftermarket Brand X hook. It has no markings from Simanco or anyone else. I'm trying to figure out where the entire upper thread is at each stage after the hook catches the loop at the needle.