Lower thread

[Romana]

Hello. Could someone please help me with some advice on why the lower thread goes up in the middle (red) and not on the left (blue) on my Pfaff 335? The photo of the hook is from the internet, I just needed to read the points.

Edited Saturday at 08:10 PM by Romana

[friquant]

Are you having trouble getting the machine to stitch properly, or are you asking about the fundamentals of how a sewing machine forms stitches?

 

If the former, I suggest making a close-up video with the bobbin cover removed, while you turn the hand wheel VERY slowly and smoothly. Here is a great example of such a video:

 

[Romana]

I can't even record a video to make it look good. What I mean is that the machine sews well for a while and then seems to jerk in places. I attributed it to the lower bobbin thread coming out in the middle.

[Romana]

Here the lower thread goes correctly, but after a while it jumps to the middle

[friquant]

Does it jump to the middle when going in reverse?

After it jumps to the middle, does it ever revert to its former position?

When the lower thread is in the middle, does it interfere with the top thread clearing the bobbin case latch?

[friquant]

Which direction is your bobbin inserted?

Here is a screenshot of the pfaff 335 manual showing the correct orientation. If inserted the opposite direction, the thread can slide out of the bobbin tensioner, which is bad.

[Romana]

sometimes it jumps back, but mostly it stays in the middle. The twitches are only when the thread is in the middle

[Wizcrafts]

5 hours ago, Romana said:

sometimes it jumps back, but mostly it stays in the middle. The twitches are only when the thread is in the middle

Try reversing the direction of the bobbin. It may need to go in opposite to the way you already inserted it. I usually insert bobbins so that the thread makes  are sharp turn backwards towards the slot leading to the bobbin tension spring. This back force tends to keep the bobbin thread well placed under that spring leading to more reliable stitches.

[Michiel]

I have had similar issues with a adler 69 (which is very like your machine) 

in my case my check-spring which was not working properly , after i fixed that it was solved

 

[Romana]

I tried three different spool cases and it's still the same, but I'll try turning it again. ☺️❤️